we are writing some API which required sessionId in header and some other data in body.
Is it possible to have only one class automatically parsed partially from header and from body?
Something like:
[HttpGet("messages")]
[Produces("application/json")]
[Consumes("application/json")]
[Authorize(Policy = nameof(SessionHeaderKeyHandler))]
public async Task<ActionResult<MessageData>> GetPendingClockInMessages(PendingMessagesData pendingMessagesRequest)
{
some body...
}
with request class like:
public class PendingMessagesData
{
[FromHeader]
public string SessionId { get; set; }
[FromBody]
public string OrderBy { get; set; }
}
I know, it is possible to do this, but it means, that I have to pass SessionId into the other methods as a parameter, instead of pass only one object. And we would have to do that in every API call.
public async Task<ActionResult<MessageData>> GetPendingClockInMessages(
[FromHeader] string sessionId,
[FromBody] PendingMessagesData pendingMessagesRequest)
{
some body...
}
Thank you,
Jakub
we are writing some API which required sessionId in header and some other data in body. Is it possible to have only one class automatically parsed partially from header and from body
Your GetPendingClockInMessages is annotated with a [HttpGet("messages")]. However, a HTTP GET method has no body at all. Also, it can't consume application/json. Please change it to HttpPost("messages")
Typically, SessionId is not passed in header of Session: {SessionId} like other HTTP headers. Session are encrypted via IDataProtector. In other words, you can't get it by Request.Headers["SessionId"].
Apart from the above two facts, you can create a custom model binder to do that.
Since the Session doesn't come from header directly, let's create a custom [FromSession] attribute to replace your [FromHeader]
public class FromSessionAttribute : Attribute, IBindingSourceMetadata
{
public static readonly BindingSource Instance = new BindingSource("FromSession", "FromSession Binding Source", true, true);
public BindingSource BindingSource { get { return FromSessionAttribute.Instance; } }
}
And since you're consuming application/json, let's create a binder as below:
public class MyModelBinder : IModelBinder
{
private readonly JsonOptions jsonOptions;
public MyModelBinder(IOptions<JsonOptions> jsonOptions)
{
this.jsonOptions = jsonOptions.Value;
}
public async Task BindModelAsync(ModelBindingContext bindingContext)
{
var type = bindingContext.ModelType;
var pis = type.GetProperties();
var result= Activator.CreateInstance(type);
var body= bindingContext.ActionContext.HttpContext.Request.Body;
var stream = new System.IO.StreamReader(body);
var json = await stream.ReadToEndAsync();
try{
result = JsonSerializer.Deserialize(json, type, this.jsonOptions.JsonSerializerOptions);
} catch(Exception){
// in case we want to pass string directly. if you don't need this feature, remove this branch
if(pis.Count()==2){
var prop = pis
.Where(pi => pi.PropertyType == typeof(string) )
.Where(pi => !pi.GetCustomAttributesData().Any(ca => ca.AttributeType == typeof(FromSessionAttribute)))
.FirstOrDefault();
if(prop != null){
prop.SetValue( result ,json.Trim('"'));
}
} else{
bindingContext.ModelState.AddModelError("", $"cannot deserialize from body");
return;
}
}
var sessionId = bindingContext.HttpContext.Session.Id;
if (string.IsNullOrEmpty(sessionId)) {
bindingContext.ModelState.AddModelError("sessionId", $"cannot get SessionId From Session");
return;
} else {
var props = pis.Where(pi => {
var attributes = pi.GetCustomAttributesData();
return attributes.Any( ca => ca.AttributeType == typeof(FromSessionAttribute));
});
foreach(var prop in props) {
prop.SetValue(result, sessionId);
}
bindingContext.Result = ModelBindingResult.Success(result);
}
}
}
How to use
Decorate the property with a FromSession to indicate that we want to get the property via HttpContext.Sessino.Id:
public class PendingMessagesData
{
[FromBody]
public string OrderBy { get; set; } // or a complex model: `public MySub Sub{ get; set; }`
[FromSession]
public string SessionId { get; set; }
}
Finally, add a modelbinder on the action method parameter:
[HttpPost("messages")]
[Produces("application/json")]
[Consumes("application/json")]
public async Task<ActionResult> GetPendingClockInMessages([ModelBinder(typeof(MyModelBinder))]PendingMessagesData pendingMessagesRequest)
{
return Json(pendingMessagesRequest);
}
Personally, I would prefer another way, i.e, creating a FromSessionBinderProvider so that I can implement this without too much effort. :
public class FromSessionDataModelBinder : IModelBinder
{
public Task BindModelAsync(ModelBindingContext bindingContext)
{
var sessionId = bindingContext.HttpContext.Session.Id;
if (string.IsNullOrEmpty(sessionId)) {
bindingContext.ModelState.AddModelError(sessionId, $"cannot get SessionId From Session");
} else {
bindingContext.Result = ModelBindingResult.Success(sessionId);
}
return Task.CompletedTask;
}
}
public class FromSessionBinderProvider : IModelBinderProvider
{
public IModelBinder GetBinder(ModelBinderProviderContext context)
{
if (context == null) { throw new ArgumentNullException(nameof(context)); }
var hasFromSessionAttribute = context.BindingInfo?.BindingSource == FromSessionAttribute.Instance;
return hasFromSessionAttribute ?
new BinderTypeModelBinder(typeof(FromSessionDataModelBinder)) :
null;
}
}
(if you're able to remove the [ApiController] attribute, this way is more easier).
I m new to Azure Function. I m used to code with WebApi where I have an ActionExecutingContext which helps to validate the ModelState.
I created an ActionFilterAttribute which do it automatically:
[AttributeUsage(AttributeTargets.All, AllowMultiple = false)]
public class ValidateModelStateAttribute : ActionFilterAttribute
{
public override void OnActionExecuting(ActionExecutingContext context)
{
if (!context.ModelState.IsValid)
{
//Do something
}
}
}
How can I do that or something similar with Azure function?
For example with this DTO with a name property set as Required:
public class TestDto
{
[Required]
public string Name { get; set; }
}
I created an easy extension which validate the object and set an out parameter with the collection of errors.
public static class ObjectExtensions
{
public static bool IsValid(this object o, out ICollection<ValidationResult> validationResults)
{
validationResults = new List<ValidationResult>();
return Validator.TryValidateObject(o, new ValidationContext(o, null, null), validationResults, true);
}
}
So in my Azure function, here is what I have:
[FunctionName("Create")]
public async Task<IActionResult> CreateAsync(
[HttpTrigger(AuthorizationLevel.Anonymous, "post", Route = "test/")] TestDto dto,
CancellationToken cts,
ILogger log)
{
if (!dto.IsValid(validationResults: out var validationResults))
{
return new BadRequestObjectResult($"{nameof(TestDto)} is invalid: {string.Join(", ", validationResults.Select(s => s.ErrorMessage))}");
}
var result = await _testManager.CreateAsync(new Test() { Name = dto.Name }, cts);
return new OkObjectResult(result);
}
I think you could also write a custom attribute for this that implements the OnExecutingAsync and perform the validation in there, see https://www.c-sharpcorner.com/article/do-you-know-azure-function-have-function-filters/
I was following this example
example code:
public class Global : HttpApplication
{
private Poster _posterDetails;
private Posting _postingDetails;
private Property _propertyDetails;
protected void Application_PostRequestHandlerExecute(object sender, EventArgs e)
{
if (HttpContext.Current.Session == null) return;
_posterDetails = HttpContext.Current.Session["Poster"] as Poster;
_postingDetails = HttpContext.Current.Session["Posting"] as Posting;
_propertyDetails = HttpContext.Current.Session["Property"] as Property;
}
}
these session variables are littered throughout the app and I need to abstract the retrieval of them. Say, later I get them from a db instead of the current session.
Session is baked into the Page or Context. How do I inject that dependency into the concrete implementation of a possible current property getter.
Create an abstraction around HttpContext:
public interface IHttpContextFactory
{
HttpContextBase Create();
}
public class HttpContextFactory
: IHttpContextFactory
{
public HttpContextBase Create()
{
return new HttpContextWrapper(HttpContext.Current);
}
}
Then inject it into a specialized service for these settings.
public interface ISettings
{
T GetValue<T>(string key);
void SetValue<T>(string key, T value);
}
public class ContextSettings
: ISettings
{
private readonly IHttpContextFactory httpContextFactory;
private HttpContextBase context;
public RequestCache(
IHttpContextFactory httpContextFactory
)
{
if (httpContextFactory == null)
throw new ArgumentNullException("httpContextFactory");
this.httpContextFactory = httpContextFactory;
}
protected HttpContextBase Context
{
get
{
if (this.context == null)
{
this.context = this.httpContextFactory.Create();
}
return context;
}
}
public virtual T GetValue<T>(string key)
{
if (this.Context.Session.Contains(key))
{
return (T)this.Context.Session[key];
}
return default(T);
}
public virtual void SetValue<T>(string key, T value)
{
this.Context.Session[key] = value;
}
}
It will later be possible to replace the service with another storage mechanism by implementing ISettings and providing different constructor dependencies. Note that changing the constructor signature does not require a different interface.
That said, you should provide another service (or perhaps more than one) that takes ISettings as a dependency so you can make explicit properties. You should aim to provide focused sets of related properties for specific purposes. Your application also shouldn't have to know the type of property in order to retrieve its value - it should just call a property that hides those details.
public class SomeSettingsService: ISomeSettingsService
{
private readonly ISettings settings;
public SomeSettingsService(ISettings settings)
{
if (settings == null)
throw new ArgumentNullException("settings");
this.settings = settings;
}
public Poster Poster
{
get { return this.settings.GetValue<Poster>("Poster"); }
set { this.settings.SetValue<Poster>("Poster", value); }
}
public Posting Posting
{
get { return this.settings.GetValue<Posting>("Posting"); }
set { this.settings.SetValue<Posting>("Posting", value); }
}
public Property Property
{
get { return this.settings.GetValue<Property>("Property"); }
set { this.settings.SetValue<Property>("Property", value); }
}
}
Not sure if this is what you are asking... What I often do is create a service:
public interface ISessionService
{
object Get(string key);
void Save(string key, object value);
}
And then I implement this, which calls HttpContext.Current.Session[key] and returns the value. It shouldn't be hard to create a Get<T>(string key) to return an object either. Break all of your dependencies to use this (which is the hard part).
There is no seamless way to break the dependency... it has to be through a manual change.
When using Json.Net, I understand how to get the $type property into the rendered json, but is there a way to change that field name? I need to use "__type" instead of "$type".
http://json.codeplex.com/workitem/22429
"I would rather keep $type hard coded and consistent."
Consistent with what I wonder?
http://json.codeplex.com/workitem/21989
I would rather not - I think this is too specific to me and I don't
want to go overboard with settings. At some point I will probably
implement this - http://json.codeplex.com/workitem/21856 - allowing
people to read/write there own meta properties in the JSON and you
could reimplement type name handling with a new property name. The
other option is just to modify the source code for yourself to have
that property name.
And more recently, Issue #36: Customizable $type property name feature:
I'd rather not
This is my solution...
json.Replace("\"$type\": \"", "\"type\": \"");
Looks like this is hardcoded as public const string TypePropertyName = "$type"; in Newtonsoft.Json.Serialization.JsonTypeReflector which is internal static class unfortunately.
I needed this myself, and the only thing I can think of is having custom modified version of json.net itself. Which is of course is a major pita.
when serializing, there is a nice way to override the property name:
public class CustomJsonWriter : JsonTextWriter
{
public CustomJsonWriter(TextWriter writer) : base(writer)
{
}
public override void WritePropertyName(string name, bool escape)
{
if (name == "$type") name = "__type";
base.WritePropertyName(name, escape);
}
}
var serializer = new JsonSerializer();
var writer = new StreamWriter(stream) { AutoFlush = true };
serializer.Serialize(new CustomJsonWriter(writer), objectToSerialize);
I haven't tried deserialization yet, but in worst case I could use:
json.Replace("\"__type": \"", "\"type\": \"$type\");
I had to do this for my UI REST API as Angular.js disregards fields names starting with a dollar sign ($).
So here's a solution that renames $type to __type for the whole Web API and works both for serialization and deserialization.
In order to be able to use a custom JsonWriter and a custom JsonReader (as proposed in the other answers to this question), we have to inherit the JsonMediaTypeFormatter and override the corresponding methods:
internal class CustomJsonNetFormatter : JsonMediaTypeFormatter
{
public override JsonReader CreateJsonReader(Type type, Stream readStream, Encoding effectiveEncoding)
{
return new CustomJsonReader(readStream, effectiveEncoding);
}
public override JsonWriter CreateJsonWriter(Type type, Stream writeStream, Encoding effectiveEncoding)
{
return new CustomJsonWriter(writeStream, effectiveEncoding);
}
private class CustomJsonWriter : JsonTextWriter
{
public CustomJsonWriter(Stream writeStream, Encoding effectiveEncoding)
: base(new StreamWriter(writeStream, effectiveEncoding))
{
}
public override void WritePropertyName(string name, bool escape)
{
if (name == "$type") name = "__type";
base.WritePropertyName(name, escape);
}
}
private class CustomJsonReader : JsonTextReader
{
public CustomJsonReader(Stream readStream, Encoding effectiveEncoding)
: base(new StreamReader(readStream, effectiveEncoding))
{
}
public override bool Read()
{
var hasToken = base.Read();
if (hasToken && TokenType == JsonToken.PropertyName && Value != null && Value.Equals("__type"))
{
SetToken(JsonToken.PropertyName, "$type");
}
return hasToken;
}
}
}
Of course you need to register the custom formatter in your WebApiConfig. So we replace the default Json.NET formatter with our custom one:
config.Formatters.Remove(config.Formatters.JsonFormatter);
config.Formatters.Add(new CustomJsonNetFormatter());
Done.
We had a need for this so I created a custom JsonReader. We're are using rest in our MS web services with complex data models and needed to replace the "__type" property with "$type."
class MSJsonReader : JsonTextReader
{
public MSJsonTextReader(TextReader reader) : base(reader) { }
public override bool Read()
{
var hasToken = base.Read();
if (hasToken && base.TokenType == JsonToken.PropertyName && base.Value != null && base.Value.Equals("__type"))
base.SetToken(JsonToken.PropertyName, "$type");
return hasToken;
}
}
Here is how we use it.
using(JsonReader jr = new MSJsonTextReader(sr))
{
JsonSerializer s = new JsonSerializer();
s.DateFormatHandling = DateFormatHandling.MicrosoftDateFormat;
s.NullValueHandling = NullValueHandling.Ignore;
s.TypeNameHandling = TypeNameHandling.Auto; // Important!
s.Binder = new MSRestToJsonDotNetSerializationBinder("Server.DataModelsNamespace", "Client.GeneratedModelsNamespace");
T deserialized = s.Deserialize<T>(jr);
return deserialized;
}
Here is our MSRestToJsonDotNetSerializationBinder that completes the compatibility between MS rest and Json.Net.
class MSRestToJsonDotNetSerializationBinder : System.Runtime.Serialization.SerializationBinder
{
public string ServiceNamespace { get; set; }
public string LocalNamespace { get; set; }
public MSRestToJsonDotNetSerializationBinder(string serviceNamespace, string localNamespace)
{
if (serviceNamespace.EndsWith("."))
serviceNamespace = serviceNamespace.Substring(0, -1);
if(localNamespace.EndsWith("."))
localNamespace = localNamespace.Substring(0, -1);
ServiceNamespace = serviceNamespace;
LocalNamespace = localNamespace;
}
public override void BindToName(Type serializedType, out string assemblyName, out string typeName)
{
assemblyName = null;
typeName = string.Format("{0}:#{1}", serializedType.Name, ServiceNamespace); // MS format
}
public override Type BindToType(string assemblyName, string typeName)
{
string jsonDotNetType = string.Format("{0}.{1}", LocalNamespace, typeName.Substring(0, typeName.IndexOf(":#")));
return Type.GetType(jsonDotNetType);
}
}
You could also do it this way:
[JsonConverter(typeof(JsonSubtypes), "ClassName")]
public class Annimal
{
public virtual string ClassName { get; }
public string Color { get; set; }
}
You will need the JsonSubtypes
converter that is not part of Newtonsoft.Json project.
There is another option that allows to serialize custom type property name in Json.NET. The idea is do not write default $type property, but introduce type name as property of class itself.
Suppose we have a Location class:
public class Location
{
public double Latitude { get; set; }
public double Longitude { get; set; }
}
First, we need to introduce type property name and modify the class as demonstrated below:
public class Location
{
[JsonProperty("__type")]
public string EntityTypeName
{
get
{
var typeName = string.Format("{0}, {1}", GetType().FullName, GetType().Namespace);
return typeName;
}
}
public double Latitude { get; set; }
public double Longitude { get; set; }
}
Then, set JsonSerializerSettings.TypeNameHandling to TypeNameHandling.None in order the deserializer to skip the rendering of default $type attribute.
That's it.
Example
var point = new Location() { Latitude = 51.5033630, Longitude = -0.1276250 };
var jsonLocation = JsonConvert.SerializeObject(point, new JsonSerializerSettings
{
TypeNameHandling = TypeNameHandling.None, //do not write type property(!)
});
Console.WriteLine(jsonLocation);
Result
{"__type":"Namespace.Location, Namespace","Latitude":51.503363,"Longitude":-0.127625}
Using a custom converter should get the job done.
public CustomConverter : JsonConverter
{
public override bool CanWrite => true;
public override bool CanRead => true;
public override object ReadJson(JsonReader reader,
Type objectType,
object existingValue,
JsonSerializer serializer)
=> throw new NotImplementedException();
public override void WriteJson(JsonWriter writer,
object value,
JsonSerializer serializer)
{
var jOjbect = (JObject)JToken.FromObject(value);
jOjbect.Add(new JProperty("type", value.GetType().Name));
jOjbect.WriteTo(writer);
}
}
I'm using ASP.NET MVC and I'd like all user entered string fields to be trimmed before they're inserted into the database. And since I have many data entry forms, I'm looking for an elegant way to trim all strings instead of explicitly trimming every user supplied string value. I'm interested to know how and when people are trimming strings.
I thought about perhaps creating a custom model binder and trimming any string values there...that way, all my trimming logic is contained in one place. Is this a good approach? Are there any code samples that do this?
public class TrimModelBinder : DefaultModelBinder
{
protected override void SetProperty(ControllerContext controllerContext,
ModelBindingContext bindingContext,
System.ComponentModel.PropertyDescriptor propertyDescriptor, object value)
{
if (propertyDescriptor.PropertyType == typeof(string))
{
var stringValue = (string)value;
if (!string.IsNullOrWhiteSpace(stringValue))
{
value = stringValue.Trim();
}
else
{
value = null;
}
}
base.SetProperty(controllerContext, bindingContext,
propertyDescriptor, value);
}
}
How about this code?
ModelBinders.Binders.DefaultBinder = new TrimModelBinder();
Set global.asax Application_Start event.
This is #takepara same resolution but as an IModelBinder instead of DefaultModelBinder so that adding the modelbinder in global.asax is through
ModelBinders.Binders.Add(typeof(string),new TrimModelBinder());
The class:
public class TrimModelBinder : IModelBinder
{
public object BindModel(ControllerContext controllerContext,
ModelBindingContext bindingContext)
{
ValueProviderResult valueResult = bindingContext.ValueProvider.GetValue(bindingContext.ModelName);
if (valueResult== null || valueResult.AttemptedValue==null)
return null;
else if (valueResult.AttemptedValue == string.Empty)
return string.Empty;
return valueResult.AttemptedValue.Trim();
}
}
based on #haacked post:
http://haacked.com/archive/2011/03/19/fixing-binding-to-decimals.aspx
One improvement to #takepara answer.
Somewere in project:
public class NoTrimAttribute : Attribute { }
In TrimModelBinder class change
if (propertyDescriptor.PropertyType == typeof(string))
to
if (propertyDescriptor.PropertyType == typeof(string) && !propertyDescriptor.Attributes.Cast<object>().Any(a => a.GetType() == typeof(NoTrimAttribute)))
and you can mark properties to be excluded from trimming with [NoTrim] attribute.
In ASP.Net Core 2 this worked for me. I'm using the [FromBody] attribute in my controllers and JSON input. To override the string handling in the JSON deserialization I registered my own JsonConverter:
services.AddMvcCore()
.AddJsonOptions(options =>
{
options.SerializerSettings.Converters.Insert(0, new TrimmingStringConverter());
})
And this is the converter:
public class TrimmingStringConverter : JsonConverter
{
public override bool CanRead => true;
public override bool CanWrite => false;
public override bool CanConvert(Type objectType) => objectType == typeof(string);
public override object ReadJson(JsonReader reader, Type objectType,
object existingValue, JsonSerializer serializer)
{
if (reader.Value is string value)
{
return value.Trim();
}
return reader.Value;
}
public override void WriteJson(JsonWriter writer, object value,
JsonSerializer serializer)
{
throw new NotImplementedException();
}
}
With improvements in C# 6, you can now write a very compact model binder that will trim all string inputs:
public class TrimStringModelBinder : IModelBinder
{
public object BindModel(ControllerContext controllerContext, ModelBindingContext bindingContext)
{
var value = bindingContext.ValueProvider.GetValue(bindingContext.ModelName);
var attemptedValue = value?.AttemptedValue;
return string.IsNullOrWhiteSpace(attemptedValue) ? attemptedValue : attemptedValue.Trim();
}
}
You need to include this line somewhere in Application_Start() in your Global.asax.cs file to use the model binder when binding strings:
ModelBinders.Binders.Add(typeof(string), new TrimStringModelBinder());
I find it is better to use a model binder like this, rather than overriding the default model binder, because then it will be used whenever you are binding a string, whether that's directly as a method argument or as a property on a model class. However, if you override the default model binder as other answers here suggest, that will only work when binding properties on models, not when you have a string as an argument to an action method
Edit: a commenter asked about dealing with the situation when a field should not be validated. My original answer was reduced to deal just with the question the OP had posed, but for those who are interested, you can deal with validation by using the following extended model binder:
public class TrimStringModelBinder : IModelBinder
{
public object BindModel(ControllerContext controllerContext, ModelBindingContext bindingContext)
{
var shouldPerformRequestValidation = controllerContext.Controller.ValidateRequest && bindingContext.ModelMetadata.RequestValidationEnabled;
var unvalidatedValueProvider = bindingContext.ValueProvider as IUnvalidatedValueProvider;
var value = unvalidatedValueProvider == null ?
bindingContext.ValueProvider.GetValue(bindingContext.ModelName) :
unvalidatedValueProvider.GetValue(bindingContext.ModelName, !shouldPerformRequestValidation);
var attemptedValue = value?.AttemptedValue;
return string.IsNullOrWhiteSpace(attemptedValue) ? attemptedValue : attemptedValue.Trim();
}
}
Another variant of #takepara's answer but with a different twist:
1) I prefer the opt-in "StringTrim" attribute mechanism (rather than the opt-out "NoTrim" example of #Anton).
2) An additional call to SetModelValue is required to ensure the ModelState is populated correctly and the default validation/accept/reject pattern can be used as normal, i.e. TryUpdateModel(model) to apply and ModelState.Clear() to accept all changes.
Put this in your entity/shared library:
/// <summary>
/// Denotes a data field that should be trimmed during binding, removing any spaces.
/// </summary>
/// <remarks>
/// <para>
/// Support for trimming is implmented in the model binder, as currently
/// Data Annotations provides no mechanism to coerce the value.
/// </para>
/// <para>
/// This attribute does not imply that empty strings should be converted to null.
/// When that is required you must additionally use the <see cref="System.ComponentModel.DataAnnotations.DisplayFormatAttribute.ConvertEmptyStringToNull"/>
/// option to control what happens to empty strings.
/// </para>
/// </remarks>
[AttributeUsage(AttributeTargets.Property | AttributeTargets.Field, AllowMultiple = false)]
public class StringTrimAttribute : Attribute
{
}
Then this in your MVC application/library:
/// <summary>
/// MVC model binder which trims string values decorated with the <see cref="StringTrimAttribute"/>.
/// </summary>
public class StringTrimModelBinder : IModelBinder
{
/// <summary>
/// Binds the model, applying trimming when required.
/// </summary>
public object BindModel(ControllerContext controllerContext, ModelBindingContext bindingContext)
{
// Get binding value (return null when not present)
var propertyName = bindingContext.ModelName;
var originalValueResult = bindingContext.ValueProvider.GetValue(propertyName);
if (originalValueResult == null)
return null;
var boundValue = originalValueResult.AttemptedValue;
// Trim when required
if (!String.IsNullOrEmpty(boundValue))
{
// Check for trim attribute
if (bindingContext.ModelMetadata.ContainerType != null)
{
var property = bindingContext.ModelMetadata.ContainerType.GetProperties()
.FirstOrDefault(propertyInfo => propertyInfo.Name == bindingContext.ModelMetadata.PropertyName);
if (property != null && property.GetCustomAttributes(true)
.OfType<StringTrimAttribute>().Any())
{
// Trim when attribute set
boundValue = boundValue.Trim();
}
}
}
// Register updated "attempted" value with the model state
bindingContext.ModelState.SetModelValue(propertyName, new ValueProviderResult(
originalValueResult.RawValue, boundValue, originalValueResult.Culture));
// Return bound value
return boundValue;
}
}
If you don't set the property value in the binder, even when you don't want to change anything, you will block that property from ModelState altogether! This is because you are registered as binding all string types, so it appears (in my testing) that the default binder will not do it for you then.
Extra info for anyone searching how to do this in ASP.NET Core 1.0. Logic has changed quite a lot.
I wrote a blog post about how to do it, it explains things in bit more detailed
So ASP.NET Core 1.0 solution:
Model binder to do the actual trimming
public class TrimmingModelBinder : ComplexTypeModelBinder
{
public TrimmingModelBinder(IDictionary propertyBinders) : base(propertyBinders)
{
}
protected override void SetProperty(ModelBindingContext bindingContext, string modelName, ModelMetadata propertyMetadata, ModelBindingResult result)
{
if(result.Model is string)
{
string resultStr = (result.Model as string).Trim();
result = ModelBindingResult.Success(resultStr);
}
base.SetProperty(bindingContext, modelName, propertyMetadata, result);
}
}
Also you need Model Binder Provider in the latest version, this tells that should this binder be used for this model
public class TrimmingModelBinderProvider : IModelBinderProvider
{
public IModelBinder GetBinder(ModelBinderProviderContext context)
{
if (context == null)
{
throw new ArgumentNullException(nameof(context));
}
if (context.Metadata.IsComplexType && !context.Metadata.IsCollectionType)
{
var propertyBinders = new Dictionary();
foreach (var property in context.Metadata.Properties)
{
propertyBinders.Add(property, context.CreateBinder(property));
}
return new TrimmingModelBinder(propertyBinders);
}
return null;
}
}
Then it has to be registered in Startup.cs
services.AddMvc().AddMvcOptions(options => {
options.ModelBinderProviders.Insert(0, new TrimmingModelBinderProvider());
});
In case of MVC Core
Binder:
using Microsoft.AspNetCore.Mvc.ModelBinding;
using System;
using System.Threading.Tasks;
public class TrimmingModelBinder
: IModelBinder
{
private readonly IModelBinder FallbackBinder;
public TrimmingModelBinder(IModelBinder fallbackBinder)
{
FallbackBinder = fallbackBinder ?? throw new ArgumentNullException(nameof(fallbackBinder));
}
public Task BindModelAsync(ModelBindingContext bindingContext)
{
if (bindingContext == null)
{
throw new ArgumentNullException(nameof(bindingContext));
}
var valueProviderResult = bindingContext.ValueProvider.GetValue(bindingContext.ModelName);
if (valueProviderResult != null &&
valueProviderResult.FirstValue is string str &&
!string.IsNullOrEmpty(str))
{
bindingContext.Result = ModelBindingResult.Success(str.Trim());
return Task.CompletedTask;
}
return FallbackBinder.BindModelAsync(bindingContext);
}
}
Provider:
using Microsoft.AspNetCore.Mvc.ModelBinding;
using Microsoft.AspNetCore.Mvc.ModelBinding.Binders;
using System;
public class TrimmingModelBinderProvider
: IModelBinderProvider
{
public IModelBinder GetBinder(ModelBinderProviderContext context)
{
if (context == null)
{
throw new ArgumentNullException(nameof(context));
}
if (!context.Metadata.IsComplexType && context.Metadata.ModelType == typeof(string))
{
return new TrimmingModelBinder(new SimpleTypeModelBinder(context.Metadata.ModelType));
}
return null;
}
}
Registration function:
public static void AddStringTrimmingProvider(this MvcOptions option)
{
var binderToFind = option.ModelBinderProviders
.FirstOrDefault(x => x.GetType() == typeof(SimpleTypeModelBinderProvider));
if (binderToFind == null)
{
return;
}
var index = option.ModelBinderProviders.IndexOf(binderToFind);
option.ModelBinderProviders.Insert(index, new TrimmingModelBinderProvider());
}
Register:
service.AddMvc(option => option.AddStringTrimmingProvider())
I created value providers to trim the query string parameter values and the form values. This was tested with ASP.NET Core 3 and works perfectly.
public class TrimmedFormValueProvider
: FormValueProvider
{
public TrimmedFormValueProvider(IFormCollection values)
: base(BindingSource.Form, values, CultureInfo.InvariantCulture)
{ }
public override ValueProviderResult GetValue(string key)
{
ValueProviderResult baseResult = base.GetValue(key);
string[] trimmedValues = baseResult.Values.Select(v => v?.Trim()).ToArray();
return new ValueProviderResult(new StringValues(trimmedValues));
}
}
public class TrimmedQueryStringValueProvider
: QueryStringValueProvider
{
public TrimmedQueryStringValueProvider(IQueryCollection values)
: base(BindingSource.Query, values, CultureInfo.InvariantCulture)
{ }
public override ValueProviderResult GetValue(string key)
{
ValueProviderResult baseResult = base.GetValue(key);
string[] trimmedValues = baseResult.Values.Select(v => v?.Trim()).ToArray();
return new ValueProviderResult(new StringValues(trimmedValues));
}
}
public class TrimmedFormValueProviderFactory
: IValueProviderFactory
{
public Task CreateValueProviderAsync(ValueProviderFactoryContext context)
{
if (context.ActionContext.HttpContext.Request.HasFormContentType)
context.ValueProviders.Add(new TrimmedFormValueProvider(context.ActionContext.HttpContext.Request.Form));
return Task.CompletedTask;
}
}
public class TrimmedQueryStringValueProviderFactory
: IValueProviderFactory
{
public Task CreateValueProviderAsync(ValueProviderFactoryContext context)
{
context.ValueProviders.Add(new TrimmedQueryStringValueProvider(context.ActionContext.HttpContext.Request.Query));
return Task.CompletedTask;
}
}
Then register the value provider factories in the ConfigureServices() function in Startup.cs
services.AddControllersWithViews(options =>
{
int formValueProviderFactoryIndex = options.ValueProviderFactories.IndexOf(options.ValueProviderFactories.OfType<FormValueProviderFactory>().Single());
options.ValueProviderFactories[formValueProviderFactoryIndex] = new TrimmedFormValueProviderFactory();
int queryStringValueProviderFactoryIndex = options.ValueProviderFactories.IndexOf(options.ValueProviderFactories.OfType<QueryStringValueProviderFactory>().Single());
options.ValueProviderFactories[queryStringValueProviderFactoryIndex] = new TrimmedQueryStringValueProviderFactory();
});
While reading through the excellent answers and comments above, and becoming increasingly confused, I suddenly thought, hey, I wonder if there's a jQuery solution. So for others who, like me, find ModelBinders a bit bewildering, I offer the following jQuery snippet that trims the input fields before the form gets submitted.
$('form').submit(function () {
$(this).find('input:text').each(function () {
$(this).val($.trim($(this).val()));
})
});
Late to the party, but the following is a summary of adjustments required for MVC 5.2.3 if you are to handle the skipValidation requirement of the build-in value providers.
public class TrimStringModelBinder : IModelBinder
{
public object BindModel(ControllerContext controllerContext, ModelBindingContext bindingContext)
{
// First check if request validation is required
var shouldPerformRequestValidation = controllerContext.Controller.ValidateRequest &&
bindingContext.ModelMetadata.RequestValidationEnabled;
// determine if the value provider is IUnvalidatedValueProvider, if it is, pass in the
// flag to perform request validation (e.g. [AllowHtml] is set on the property)
var unvalidatedProvider = bindingContext.ValueProvider as IUnvalidatedValueProvider;
var valueProviderResult = unvalidatedProvider?.GetValue(bindingContext.ModelName, !shouldPerformRequestValidation) ??
bindingContext.ValueProvider.GetValue(bindingContext.ModelName);
return valueProviderResult?.AttemptedValue?.Trim();
}
}
Global.asax
protected void Application_Start()
{
...
ModelBinders.Binders.Add(typeof(string), new TrimStringModelBinder());
...
}
Update: This answer is out of date for recent versions of ASP.NET Core. Use Bassem's answer instead.
For ASP.NET Core, replace the ComplexTypeModelBinderProvider with a provider that trims strings.
In your startup code ConfigureServices method, add this:
services.AddMvc()
.AddMvcOptions(s => {
s.ModelBinderProviders[s.ModelBinderProviders.TakeWhile(p => !(p is ComplexTypeModelBinderProvider)).Count()] = new TrimmingModelBinderProvider();
})
Define TrimmingModelBinderProvider like this:
/// <summary>
/// Used in place of <see cref="ComplexTypeModelBinderProvider"/> to trim beginning and ending whitespace from user input.
/// </summary>
class TrimmingModelBinderProvider : IModelBinderProvider
{
class TrimmingModelBinder : ComplexTypeModelBinder
{
public TrimmingModelBinder(IDictionary<ModelMetadata, IModelBinder> propertyBinders) : base(propertyBinders) { }
protected override void SetProperty(ModelBindingContext bindingContext, string modelName, ModelMetadata propertyMetadata, ModelBindingResult result)
{
var value = result.Model as string;
if (value != null)
result = ModelBindingResult.Success(value.Trim());
base.SetProperty(bindingContext, modelName, propertyMetadata, result);
}
}
public IModelBinder GetBinder(ModelBinderProviderContext context)
{
if (context.Metadata.IsComplexType && !context.Metadata.IsCollectionType) {
var propertyBinders = new Dictionary<ModelMetadata, IModelBinder>();
for (var i = 0; i < context.Metadata.Properties.Count; i++) {
var property = context.Metadata.Properties[i];
propertyBinders.Add(property, context.CreateBinder(property));
}
return new TrimmingModelBinder(propertyBinders);
}
return null;
}
}
The ugly part of this is the copy and paste of the GetBinder logic from ComplexTypeModelBinderProvider, but there doesn't seem to be any hook to let you avoid this.
I disagree with the solution.
You should override GetPropertyValue because the data for SetProperty could also be filled by the ModelState.
To catch the raw data from the input elements write this:
public class CustomModelBinder : System.Web.Mvc.DefaultModelBinder
{
protected override object GetPropertyValue(System.Web.Mvc.ControllerContext controllerContext, System.Web.Mvc.ModelBindingContext bindingContext, System.ComponentModel.PropertyDescriptor propertyDescriptor, System.Web.Mvc.IModelBinder propertyBinder)
{
object value = base.GetPropertyValue(controllerContext, bindingContext, propertyDescriptor, propertyBinder);
string retval = value as string;
return string.IsNullOrWhiteSpace(retval)
? value
: retval.Trim();
}
}
Filter by propertyDescriptor PropertyType if you are really only interested in string values but it should not matter because everything what comes in is basically a string.
There have been a lot of posts suggesting an attribute approach. Here is a package that already has a trim attribute and many others: Dado.ComponentModel.Mutations or NuGet
public partial class ApplicationUser
{
[Trim, ToLower]
public virtual string UserName { get; set; }
}
// Then to preform mutation
var user = new ApplicationUser() {
UserName = " M#X_speed.01! "
}
new MutationContext<ApplicationUser>(user).Mutate();
After the call to Mutate(), user.UserName will be mutated to m#x_speed.01!.
This example will trim whitespace and case the string to lowercase. It doesn't introduce validation, but the System.ComponentModel.Annotations can be used alongside Dado.ComponentModel.Mutations.
I posted this in another thread. In asp.net core 2, I went in a different direction. I used an action filter instead. In this case the developer can either set it globally or use as an attribute for the actions he/she wants to apply the string trimming. This code runs after the model binding has taken place, and it can update the values in the model object.
Here is my code, first create an action filter:
public class TrimInputStringsAttribute : ActionFilterAttribute
{
public override void OnActionExecuting(ActionExecutingContext context)
{
foreach (var arg in context.ActionArguments)
{
if (arg.Value is string)
{
string val = arg.Value as string;
if (!string.IsNullOrEmpty(val))
{
context.ActionArguments[arg.Key] = val.Trim();
}
continue;
}
Type argType = arg.Value.GetType();
if (!argType.IsClass)
{
continue;
}
TrimAllStringsInObject(arg.Value, argType);
}
}
private void TrimAllStringsInObject(object arg, Type argType)
{
var stringProperties = argType.GetProperties()
.Where(p => p.PropertyType == typeof(string));
foreach (var stringProperty in stringProperties)
{
string currentValue = stringProperty.GetValue(arg, null) as string;
if (!string.IsNullOrEmpty(currentValue))
{
stringProperty.SetValue(arg, currentValue.Trim(), null);
}
}
}
}
To use it, either register as global filter or decorate your actions with the TrimInputStrings attribute.
[TrimInputStrings]
public IActionResult Register(RegisterViewModel registerModel)
{
// Some business logic...
return Ok();
}
OK, I have this thing and it kinda works:
class TrimmingModelBinder : IModelBinder
{
public Task BindModelAsync (ModelBindingContext ctx)
{
if
(
ctx .ModelName is string name
&& ctx .ValueProvider .GetValue (name) .FirstValue is string v)
ctx .ModelState .SetModelValue
(
name,
new ValueProviderResult
((ctx .Result = ModelBindingResult .Success (v .Trim ())) .Model as string));
return Task .CompletedTask; }}
class AutoTrimAttribute : ModelBinderAttribute
{
public AutoTrimAttribute ()
{ this .BinderType = typeof (TrimmingModelBinder); }}
It is a shame that there is no standard feature for this though.
I adapted #Kai G's answer for System.Text.Json:
using System;
using System.Text.Json;
using System.Text.Json.Serialization;
public class TrimmedStringConverter : JsonConverter<string>
{
public override bool CanConvert(Type typeToConvert) => typeToConvert == typeof(string);
public override string Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
{
return reader.GetString() is string value ? value.Trim() : null;
}
public override void Write(Utf8JsonWriter writer, string value, JsonSerializerOptions options)
{
writer.WriteStringValue(value);
}
}