I am trying to create a custom attribute in mvc to use it's parameters in a view as breadCrumb.
well, this is the code of the attribute
[AttributeUsage(AttributeTargets.All, AllowMultiple = true)]
public class BreadCrumbAttribute : Attribute {
public BreadCrumbAttribute(string title, string parent, string url) {
this._title = title;
this._parent = parent;
this._url = url;
}
#region named parameters properties
private string _title;
public string Title {
get { return _title; }
}
private string _url;
public string Url {
get { return _url; }
}
private string _parent;
public string Parent {
get { return _parent; }
}
#endregion
#region positional parameters properties
public string Comments { get; set; }
#endregion
}
this is the call of the attribute
[BreadCrumbAttribute("tile", "parent name", "url")]
public ActionResult Index() {
//code goes here
}
this is a way of how I'd like to get the values. (this is a partial view)
System.Reflection.MemberInfo inf = typeof(ProductsController);
object[] attributes;
attributes = inf.GetCustomAttributes(typeof(BreadCrumbAttribute), false);
foreach (Object attribute in attributes) {
var bca = (BreadCrumbAttribute)attribute;
Response.Write(string.Format("{0}><a href={1}>{2}</a>", bca.Parent, bca.Url, bca.Title));
}
Unfortunately, the attribute didn't get call with the way I implement it. Although, If I add the attribute in Class instead of an Action method it worked.
How could I make it work?
Thanks
The problem is that you are using reflection to get the attributes for the class, so naturally it does not include attributes defined on the action method.
To get those, you should define an ActionFilterAttribute, and in the OnActionExecuting or OnActionExecuted method, you can use filterContext.ActionDescriptor.GetCustomAttributes() method (MSDN description here).
Note that with this solution, you will likely have two different types of attributes: The first one is the one you wrote, to define the breadcrumbs. The second is the one that looks at the attributes on the executing action and builds up the breadcrumb (and presumably adds it to the ViewModel or sticks it in HttpContext.Items or something).
Related
I have different configurations all inheriting from a base configuration that are customized in forms. I want all of these to be handled by a single action result.
[HttpPost]
public IActionResult Register(AbstractBaseConfig config)
{
...do some logic...
return View("../Home/Index");
}
However, this is not possible because you cannot base in abstract classes as a parameter to an action result. Is there any work around for this so I don't need a seperate action result for each configuration? (I still want each configuration to be it's own class, I only need access to the base class methods in the action result logic).
Basically you can't, and the reason is that MVC will try to do new AbstractBaseConfig() as part of the Data Binding process (which parses the URL or the Form Post and puts the results in a concrete object). And by definition, doing new AbstractBaseConfig() is impossible for an abstract class.
It also makes sense for other reasons, I will explain why.
You seem to expect that MVC can determine the class from the parameters that are being passed in. That is not how it works, in fact the opposite is true: the Action Method has to specify the exact class, and then the Binder will instantiate that exact class and try to bind its properties.
Suppose you had this:
public abstract class Thing { public int ID { get;set; } }
public class NamedThing : Thing { public string Name { get;set; } }
public class OtherThing : Thing { public string Name { get;set; } }
and suppose it would be allowed to use:
public IActionResult Register(Thing thing)
then what would you expect to be in thing after Data Binding: a Thing object with only the ID set? Or one of the other object types, with Name set, but how would MVC ever be able to know which class you meant?
So for all these reasons, this is not possible.
You could have a base class inherit the abstract class and all your classes inherit from that base class whilst having that base class as your parameter
Take for example
public abstract class ABase
{
public void stuff()
{
var stuff = string.Empty;
stuff = "hello";
}
public virtual void otherstuff()
{
var stuff = string.Empty;
stuff = "hello";
}
}
public class Base : ABase
{
//empty
}
public class Derived : Base
{
public void mystuff()
{
this.stuff();
}
public override void otherstuff()
{
// Custom code
}
}
public ActionResult Register(Base config)
{
}
Greetings StackOverflow,
TL;DR
In a field template control's OnLoad method how can I find the Data Control of other fields in a FormView by property or column name.
END TL;DR.
I'm trying to add a some logic to the Boolean_Edit field template so that if the property bound to it has a new attribute I made the template will inject JavaScript. The JavaScript is intended to disable all of the data controls of the column/property names listed in the attribute's ControlledFieldNames property.
This is sort of confusing so I'll share some code.
Here is the attribute class I made for this:
/// <summary>
/// Attribute used to insert javascript into an ASP.NET web page that uses Dynamic Controls so that if the field's value changes it disables (or enables)
/// other web controls on the page which correspond to the other bound property names.
/// </summary>
[AttributeUsage(AttributeTargets.Property | AttributeTargets.Field, Inherited = false, AllowMultiple = true)]
public sealed class InputRestrictorFieldAttribute : Attribute
{
public Boolean TargetEnabledState { get; set; }
public String[] ControlledFieldNames { get; set; }
public InputRestrictorFieldAttribute(Boolean targetEnabledState, params String[] controlledFieldNames)
{
this.TargetEnabledState = targetEnabledState;
this.ControlledFieldNames = controlledFieldNames;
}
}
So I might have a property in some scaffolded class like so:
[ScaffoledTable(true)]
public class Person
{
/* Other properties... */
[InputRestrictorFieldAttribute(false, new String[]
{
"StreetAddress",
"City",
"State",
"Zip"
})]
public Boolean AddressUnknown { get; set; }
public String SteetAddress { get; set; }
public String City { get; set; }
public String State { get; set; }
public String Zip { get; set; }
/* some more code */
}
Now in the Boolean_Edit.ascx.cs file I am trying to check if the currently scaffold property has the InputRestrictorFieldAttribute and if so inject JavaScript onto the page such that when the AddressUnknown CheckBox control is check is disabled the TextBox controls for StreetAddress, City, State, and Zip.
Below is what I have tried most recently.
protected override void OnLoad(EventArgs e)
{
var attributes = this.Column.Attributes;
foreach (Attribute attr in attributes)
{
if (attr is InputRestrictorFieldAttribute)
{
InputRestrictorFieldAttribute restrictor = (InputRestrictorFieldAttribute)attr;
String restrictorScriptFunctionName = String.Format(RESTRICTOR_SCRIPT_FUNCTION_NAME, ClientID);
String restrictorScript = String.Format(RESTRICTOR_SCRIPT_TEMPLATE_ONCLICK,
restrictorScriptFunctionName,
restrictor.BoundFieldNames.Aggregate("", (aggr, item) =>
{
var bc = this.NamingContainer.BindingContainer;
var ctrl = bc.FindFieldTemplate(item);
return aggr + String.Format(RESTRICTOR_SCRIPT_TEMPLATE_ELEMENT, ctrl.ClientID);
}));
Page.ClientScript.RegisterStartupScript(Page.GetType(), "restrictorScript_" + ClientID, restrictorScript, true);
CheckBox1.Attributes.Add("onchange", restrictorScriptFunctionName + "(this);");
}
}
base.OnLoad(e);
}
Now I know doing things like getting the this.NamingContainer.BindingContainer many not (or probably wont) work in other pages but for now (in the context of the Insert.aspx page template) works. this.NamingContainer.BindingContainer is the FormView1 control of the Insert.aspx page. But everything I've tried so far to get the various data dontrols or field templates, or dynamic controls by their property name it always returns null or throws an exception.
Lastly, the aggregate method is just concatenating pieces of JavaScript together so that all of the controls are deactivated using just one JavaScript function. The contents of those script are not important to this question.
there is an extension method called FindFieldTemplate see see it here
I've done a few searches but haven't seem to find anything...
Using WebApi, I would like to map an input parameter to a header value: e.g.
E.g. in controller:
public User GetUser(int id){
...
return user;
}
I want WebApi to map the id parameter to a header value (e.g. X-Auth: 1234)... rather than an URL parameter.
Is this supported?
I don't think this is supported out of the box, like for example with the [FromBody] attribute.
It seems you should be able to achieve this functionality by using Model Binders, as described here. In the model binder you have access to the request and its headers, so you should be able to read the header and set its value to the bindingContext.Model property.
Edit: Reading the article further, it seems a custom HttpParameterBinding and a ParameterBindingAttribute is a more appropriate solution, or at least I would go this way. You could implement a generic [FromHeader] attribute, which does the job. I am also fighting the same problem, so I will post my solution once I have it in place.
Edit 2: Here is my implementation:
public class FromHeaderBinding : HttpParameterBinding
{
private string name;
public FromHeaderBinding(HttpParameterDescriptor parameter, string headerName)
: base(parameter)
{
if (string.IsNullOrEmpty(headerName))
{
throw new ArgumentNullException("headerName");
}
this.name = headerName;
}
public override Task ExecuteBindingAsync(ModelMetadataProvider metadataProvider, HttpActionContext actionContext, CancellationToken cancellationToken)
{
IEnumerable<string> values;
if (actionContext.Request.Headers.TryGetValues(this.name, out values))
{
actionContext.ActionArguments[this.Descriptor.ParameterName] = values.FirstOrDefault();
}
var taskSource = new TaskCompletionSource<object>();
taskSource.SetResult(null);
return taskSource.Task;
}
}
public abstract class FromHeaderAttribute : ParameterBindingAttribute
{
private string name;
public FromHeaderAttribute(string headerName)
{
this.name = headerName;
}
public override HttpParameterBinding GetBinding(HttpParameterDescriptor parameter)
{
return new FromHeaderBinding(parameter, this.name);
}
}
public class MyHeaderAttribute : FromHeaderAttribute
{
public MyHeaderAttribute()
: base("MyHeaderName")
{
}
}
Then you can use it like this:
[HttpGet]
public IHttpActionResult GetItem([MyHeader] string headerValue)
{
...
}
Hope that helps.
WebApi on DotNet Core has a has some additional attributes for extracting data from the request. Microsoft.AspNetCore.Mvc.FromHeaderAttribute will read from the request head.
public ActionResult ReadFromHeader([FromHeader(Name = "your-header-property-name")] string data){
//Do something
}
Thank you filipov for the answer.. I took your code and modified it a bit to suit my needs. I am posting my changes here in case anyone can make use of this.
I made 2 changes.
I liked the idea of the FromHeaderAttribute, but without subclassing. I made this class public, and require the user to set the param name.
I needed to support other data types besides string. So I attempt to convert the string value to the descriptor's parameterType.
Use it like this:
[HttpGet]
public void DeleteWidget(long widgetId, [FromHeader("widgetVersion")] int version)
{
...
}
And this is my FromHeaderBinding
public class FromHeaderBinding : HttpParameterBinding
{
private readonly string _name;
public FromHeaderBinding(HttpParameterDescriptor parameter, string headerName)
: base(parameter)
{
if (string.IsNullOrEmpty(headerName)) throw new ArgumentNullException("headerName");
_name = headerName;
}
public override Task ExecuteBindingAsync(ModelMetadataProvider metadataProvider, HttpActionContext actionContext, CancellationToken cancellationToken)
{
IEnumerable<string> values;
if (actionContext.Request.Headers.TryGetValues(_name, out values))
{
var tempVal = values.FirstOrDefault();
if (tempVal != null)
{
var actionValue = Convert.ChangeType(tempVal, Descriptor.ParameterType);
actionContext.ActionArguments[Descriptor.ParameterName] = actionValue;
}
}
var taskSource = new TaskCompletionSource<object>();
taskSource.SetResult(null);
return taskSource.Task;
}
}
Is it possible to specify an object as a parameter in MVC with default values in some way?
E.g.
public virtual ViewResult Index(RequirementFilters requirementFilters)
I'd like to initialize the values of a couple of parameters on RequirementFilters?
At the moment I am doing
public virtual ViewResult Index(int status=1, bool required =false)
I wanted to create a Filter Object so I could re-use it but I can't figure out way of setting defaults for the object in the Action Parameters.
Thanks
Graeme
You could create a custom ActionFilter attribute and create an instance of your Filter Object there. You can provide some properties through the custom attribute.
Here's an example:
public class DefaultQuerySettingsAttribute : ActionFilterAttribute
{
public string ParameterName { get; set; }
public Type SettingsType { get; set; }
public int Rows { get; set; }
public string SortColumn { get; set; }
public string SortOrder { get; set; }
public bool PagingEnabled { get; set; }
public DefaultQuerySettingsAttribute()
{
this.ParameterName = "settings";
var defaultSettings = new QuerySettings();
this.Rows = defaultSettings.Rows;
this.SortColumn = defaultSettings.SortColumn;
this.SortOrder = defaultSettings.SortOrder;
this.PagingEnabled = defaultSettings.PagingEnabled;
}
public override void OnActionExecuting(ActionExecutingContext filterContext)
{
base.OnActionExecuting(filterContext);
if (filterContext.ActionParameters.ContainsKey(this.ParameterName))
{
var querySettings = filterContext.ActionParameters[this.ParameterName] as QuerySettings;
if (querySettings == null || string.IsNullOrWhiteSpace(querySettings.SortColumn))
filterContext.ActionParameters[this.ParameterName] = this.GetQuerySettings();
}
}
private QuerySettings GetQuerySettings()
{
var querySettings = (QuerySettings)Activator.CreateInstance(SettingsType ?? typeof(QuerySettings));
querySettings.Rows = Rows;
querySettings.SortColumn = SortColumn;
querySettings.SortOrder = SortOrder;
querySettings.PagingEnabled = PagingEnabled;
return querySettings;
}
}
ParameterName is the name of the argument in the action method (requirementFilters in your case).
You can also specify actual type that will be instantiated by providing SettingsType.
Users sometimes prefer to see the defaults on screen, rather than allowing the system to hide the defaults internally.
A better way of having defaults will be to actually show the defaults on int UI, in the HTML by rendering it with together with the defaults. That way when someone posts the page, the defaults which you pre-rendered is also posted and binded to the model.
So try and see if you can render with defaults whatever for you are rendering and posted to the Index action.
Finally, if you can't do it that way, what is preventing you from initializing the properties with default values in the no-arg constructor while creating the object?
EDIT
Or you can use the C# language feature the null coalescent operator to implement defaults. Look here to read about it.
As long as you don't need to change the defaults per action, you can set them in the default constructor of the Model.
There are a lot of articles devoted to working with data in MVC, and nothing about MVC 2.
So my question is: what is the proper way to handle POST-query and validate it.
Assume we have 2 actions. Both of them operates over the same entity, but each action has its own separated set of object properties that should be bound in automatic manner. For example:
Action "A" should bind only "Name" property of object, taken from POST-request
Action "B" should bind only "Date" property of object, taken from POST-request
As far as I understand - we cannot use Bind attribute in this case.
So - what are the best practices in MVC2 to handle POST-data and probably validate it?
UPD:
After Actions performed - additional logic will be applied to the objects so they become valid and ready to store in persistent layer. For action "A" - it will be setting up Date to current date.
I personally don't like using domain model classes as my view model. I find it causes problems with validation, formatting, and generally feels wrong. In fact, I'd not actually use a DateTime property on my view model at all (I'd format it as a string in my controller).
I would use two seperate view models, each with validation attributes, exposed as properties of your primary view model:
NOTE: I've left how to combining posted view-models with the main view model as an exercise for you, since there's several ways of approaching it
public class ActionAViewModel
{
[Required(ErrorMessage="Please enter your name")]
public string Name { get; set; }
}
public class ActionBViewModel
{
[Required(ErrorMessage="Please enter your date")]
// You could use a regex or custom attribute to do date validation,
// allowing you to have a custom error message for badly formatted
// dates
public string Date { get; set; }
}
public class PageViewModel
{
public ActionAViewModel ActionA { get; set; }
public ActionBViewModel ActionB { get; set; }
}
public class PageController
{
public ActionResult Index()
{
var viewModel = new PageViewModel
{
ActionA = new ActionAViewModel { Name = "Test" }
ActionB = new ActionBViewModel { Date = DateTime.Today.ToString(); }
};
return View(viewModel);
}
// The [Bind] prefix is there for when you use
// <%= Html.TextBoxFor(x => x.ActionA.Name) %>
public ActionResult ActionA(
[Bind(Prefix="ActionA")] ActionAViewModel viewModel)
{
if (ModelState.IsValid)
{
// Load model, update the Name, and commit the change
}
else
{
// Display Index with viewModel
// and default ActionBViewModel
}
}
public ActionResult ActionB(
[Bind(Prefix="ActionB")] ActionBViewModel viewModel)
{
if (ModelState.IsValid)
{
// Load model, update the Date, and commit the change
}
else
{
// Display Index with viewModel
// and default ActionAViewModel
}
}
}
One possible way to handle POST data and add validation, is with a custom model binder.
Here is a small sample of what i used recently to add custom validation to POST-form data :
public class Customer
{
public string Name { get; set; }
public DateTime Date { get; set; }
}
public class PageController : Controller
{
[HttpPost]
public ActionResult ActionA(Customer customer)
{
if(ModelState.IsValid) {
//do something with the customer
}
}
[HttpPost]
public ActionResult ActionB(Customer customer)
{
if(ModelState.IsValid) {
//do something with the customer
}
}
}
A CustomerModelBinder will be something like that:
public class CustomerModelBinder : DefaultModelBinder
{
protected override void BindProperty(ControllerContext controllerContext, ModelBindingContext bindingContext, System.ComponentModel.PropertyDescriptor propertyDescriptor)
{
if (propertyDescriptor.Name == "Name") //or date or whatever else you want
{
//Access your Name property with valueprovider and do some magic before you bind it to the model.
//To add validation errors do (simple stuff)
if(string.IsNullOrEmpty(bindingContext.ValueProvider.GetValue("Name").AttemptedValue))
bindingContext.ModelState.AddModelError("Name", "Please enter a valid name");
//Any complex validation
}
else
{
//call the usual binder otherwise. I noticed that in this way you can use DataAnnotations as well.
base.BindProperty(controllerContext, bindingContext, propertyDescriptor);
}
}
and in the global.asax put
ModelBinders.Binders.Add(typeof(Customer), new CustomerModelBinder());
If you want not to bind Name property (just Date) when you call ActionB, then just make one more custom Model Binder and in the "if" statement, put to return the null, or the already existing value, or whatever you want. Then in the controller put:
[HttpPost]
public ActionResult([ModelBinder(typeof(CustomerAModelBinder))] Customer customer)
[HttpPost]
public ActionResult([ModelBinder(typeof(CustomerBModelBinder))] Customer customer)
Where customerAmodelbinder will bind only name and customerBmodelbinder will bind only date.
This is the easiest way i have found, to validate model binding, and i have achieved some very cool results with complex view models. I bet there is something out there that i have missed, and maybe a more expert can answer.
Hope i got your question right...:)