The objective is to instantiate local:MyViewModel without constructor injection as well as without static resource.
The property element syntax version below works fine.
<Label.BindingContext>local:MyViewModel</Label.BindingContext>
My attempt with XML attribute syntax below also works.
<Label ... BindingContext="{local:MyViewModel}"/>
However Visual Studio Community warns me with
Type local:MyViewModel is used like a markup extension but does not derive from MarkupExtension.
Question:
Is it safe to ignore this warning?
Is there any trick to suppress the warning?
Here is the markup extension implementation for WPF. Check if it will work in Xamarin too.
using System;
using System.ComponentModel;
using System.Globalization;
using System.Windows;
using System.Windows.Markup;
namespace CommonCore
{
[MarkupExtensionReturnType(typeof(Type))]
public class CreateInstanceExtension : MarkupExtension
{
[ConstructorArgument("instanceType")]
[DefaultValue(null)]
public Type InstanceType { get; set; }
[ConstructorArgument("instanceValue")]
[DefaultValue(null)]
public string InstanceValue { get; set; }
public CreateInstanceExtension(Type instanceType, string instanceValue)
: this(instanceValue)
{
InstanceType = instanceType;
}
public CreateInstanceExtension(string instanceValue)
: this()
{
InstanceValue = instanceValue;
}
public CreateInstanceExtension()
{ }
private static TypeExtension typeExtension;
public override object ProvideValue(IServiceProvider serviceProvider)
{
Type type = InstanceType;
string value = InstanceValue;
if (type is null)
{
value = value?.Trim(" \t\r\n".ToCharArray());
if (!string.IsNullOrEmpty(value))
{
string typeName = null;
if (value[0] == '(')
{
int end = value.IndexOf(')');
if (end > 0)
{
typeName = value.Substring(1, end - 1);
value = value.Substring(end + 1).Trim(" \t\r\n".ToCharArray());
}
}
else
{
typeName = value;
value = null;
}
if (!string.IsNullOrEmpty(typeName))
{
(typeExtension ??= new TypeExtension()).TypeName = typeName;
type = (Type)typeExtension.ProvideValue(serviceProvider);
}
}
}
if (type is null)
{
throw new NullReferenceException("The type must be specified.");
}
if (string.IsNullOrEmpty(value))
{
return Activator.CreateInstance(type);
}
else
{
if (TypeDescriptor.GetConverter(type) is not TypeConverter converter)
{
throw new NotImplementedException("There is no TypeConverter for the specified type.");
}
var target = ((IProvideValueTarget)serviceProvider.GetService(typeof(IProvideValueTarget)))?.TargetObject as FrameworkElement;
if (target?.Language.GetEquivalentCulture() is CultureInfo culture)
return converter.ConvertFromString(null, culture, value);
return converter.ConvertFromInvariantString(value);
}
}
}
}
Usage in WPF:
<Label ... DataContext="{commcore:CreateInstance (local:MyViewModel)}"/>
<Label ... DataContext="{commcore:CreateInstance local:MyViewModel}"/>
<Label ... DataContext="{commcore:CreateInstance (sys:Double)123.456}"/>
Related
Is there a way to ignore get-only properties using the Json.NET serializer but without using JsonIgnore attributes?
For example, I have a class with these get properties:
public Keys Hotkey { get; set; }
public Keys KeyCode
{
get
{
return Hotkey & Keys.KeyCode;
}
}
public Keys ModifiersKeys
{
get
{
return Hotkey & Keys.Modifiers;
}
}
public bool Control
{
get
{
return (Hotkey & Keys.Control) == Keys.Control;
}
}
public bool Shift
{
get
{
return (Hotkey & Keys.Shift) == Keys.Shift;
}
}
public bool Alt
{
get
{
return (Hotkey & Keys.Alt) == Keys.Alt;
}
}
public Modifiers ModifiersEnum
{
get
{
Modifiers modifiers = Modifiers.None;
if (Alt) modifiers |= Modifiers.Alt;
if (Control) modifiers |= Modifiers.Control;
if (Shift) modifiers |= Modifiers.Shift;
return modifiers;
}
}
public bool IsOnlyModifiers
{
get
{
return KeyCode == Keys.ControlKey || KeyCode == Keys.ShiftKey || KeyCode == Keys.Menu;
}
}
public bool IsValidKey
{
get
{
return KeyCode != Keys.None && !IsOnlyModifiers;
}
}
Do I need to add [JsonIgnore] to all of them (I also have many other classes), or there is better way to ignore all get-only properties?
You can do this by implementing a custom IContractResolver and using that during serialization. If you subclass the DefaultContractResolver, this becomes very easy to do:
class WritablePropertiesOnlyResolver : DefaultContractResolver
{
protected override IList<JsonProperty> CreateProperties(Type type, MemberSerialization memberSerialization)
{
IList<JsonProperty> props = base.CreateProperties(type, memberSerialization);
return props.Where(p => p.Writable).ToList();
}
}
Here is a test program demonstrating how to use it:
using System;
using System.Collections.Generic;
using System.Linq;
using Newtonsoft.Json;
using Newtonsoft.Json.Serialization;
class Program
{
static void Main(string[] args)
{
Widget w = new Widget { Id = 2, Name = "Joe Schmoe" };
JsonSerializerSettings settings = new JsonSerializerSettings
{
ContractResolver = new WritablePropertiesOnlyResolver()
};
string json = JsonConvert.SerializeObject(w, settings);
Console.WriteLine(json);
}
}
class Widget
{
public int Id { get; set; }
public string Name { get; set; }
public string LowerCaseName
{
get { return (Name != null ? Name.ToLower() : null); }
}
}
Here is the output of the above. Notice that the read-only property LowerCaseName is not included in the output.
{"Id":2,"Name":"Joe Schmoe"}
Use the OptIn mode of JSON.net and you'll only need to decorate the properties you want to serialize. This isn't as good as automatically opting out all read only properties, but it can save you some work.
[JsonObject(MemberSerialization.OptIn)]
public class MyClass
{
[JsonProperty]
public string serializedProp { get; set; }
public string nonSerializedProp { get; set; }
}
Udate: Added another possibility using reflection
If the above solution still isn't quite what you're looking for, you could use reflection to make dictionary objects which would then be serialized. Of course the example below will only work for simple classes, so you would need to add recursion if your classes contain other classes. This should at least point you in the right direction.
The subroutine to put the filtered result into a dictionary:
private Dictionary<String, object> ConvertToDictionary(object classToSerialize)
{
Dictionary<String, object> resultDictionary = new Dictionary<string, object>();
foreach (var propertyInfo in classToSerialize.GetType().GetProperties(BindingFlags.Public | BindingFlags.Instance))
{
if (propertyInfo.CanWrite) resultDictionary.Add(propertyInfo.Name, propertyInfo.GetValue(classToSerialize, null));
}
return resultDictionary;
}
A snippet showing its use:
SampleClass sampleClass = new SampleClass();
sampleClass.Hotkey = Keys.A;
var toSerialize = ConvertToDictionary(sampleClass);
String resultText = JsonConvert.SerializeObject(toSerialize);
You can use a contract resolver like this:
public class ExcludeCalculatedResolver : DefaultContractResolver
{
protected override JsonProperty CreateProperty(MemberInfo member, MemberSerialization memberSerialization)
{
var property = base.CreateProperty(member, memberSerialization);
property.ShouldSerialize = _ => ShouldSerialize(member);
return property;
}
internal static bool ShouldSerialize(MemberInfo memberInfo)
{
var propertyInfo = memberInfo as PropertyInfo;
if (propertyInfo == null)
{
return false;
}
if (propertyInfo.SetMethod != null)
{
return true;
}
var getMethod = propertyInfo.GetMethod;
return Attribute.GetCustomAttribute(getMethod, typeof(CompilerGeneratedAttribute)) != null;
}
}
It will exclude calculated properties but include C#6 get only properties and all properties with a set method.
Json.net does have the ability to conditionally serialize properties without an attribute or contract resolver. This is especially useful if you don't want your project to have a dependency on Json.net.
As per the Json.net documentation
To conditionally serialize a property, add a method that returns boolean with
the same name as the property and then prefix the method name with
ShouldSerialize. The result of the method determines whether the
property is serialized. If the method returns true then the property
will be serialized, if it returns false then the property will be
skipped.
I want to create a custom server control which looks like this:
<cc:MyControl prop1="a" prop2="b">
<cc:MyItem name="xxx">
<cc:MyItem name="yyy">
<cc:MyItem name="zzz">
</cc:MyControl>
MyControl is of course implemented as a server control, however I do not want MyItem to be child controls. Rather they should exist as simple .Net objects. I have a class called MyItem, and the control has a property called Items, and when MyItem elements are declared in the markup, the objects should be instantiated and added to the collection.
The tutorials on MSDN don't actually explain how this happens. See: http://msdn.microsoft.com/en-us/library/9txe1d4x.aspx
I'd like to know:
How is <cc:MyItem> mapped to the MyItem class? Does the element in the markup have to have the same name as the object's class?
Which constructor of MyItem is called when MyItems are added declaratively, and when?
What collection types am I permitted to use to hold MyItem objects? The link above uses ArrayList, but can I use the strongly typed List instead?
Is it possible for a control to contain multiple collections?
It is so common to use class name for markup, but you can assign another name if you want, I do not explain more, if you want please comment
when asp.net compiles markup, it uses default parameter less constructor
you can use any collection type but if you want to use benefits of viewstate your collection type must implement IStateManager interface (below I wrote source of collection that I created for my self with state managing support)
Yes, your control can have multiple collections, just add required attributes as below:
(I used one of my codes, please replace names with your desired name)
if you want to have collection first of all you must define its property in your control.
imagine we have a control named CustomControl that extends Control as below:
[System.Web.UI.ParseChildrenAttribute(true)]
[System.Web.UI.PersistChildrenAttribute(false)]
public class CustomControl : Control{
private GraphCollection m_graphs;
[Bindable(false)]
[Category("Appearance")]
[DefaultValue("")]
[Localizable(true)]
[PersistenceMode(PersistenceMode.InnerProperty)]
public GraphCollection Graphs
{
get
{
if (this.m_graphs == null) {
this.m_graphs = new GraphCollection();
if (base.IsTrackingViewState) {
this.m_graphs.TrackViewState();
}
}
return this.m_graphs;
}
}
}
as you can see in above code, CustomControl has a field with name "m_graphs" with type of "GraphCollection", also a property that exposes this field
also please please pay attention to its attribute PersistenceMode that says to asp.net property "Graphs" must persisted as InnerProperty
also please pay attention to two attributes applied to CustomControl class
attribute ParseChildrenAttribute says to asp.net that nested markup, must be treated as properties and attribute PersistChildrenAttribute says to asp.net that nested markups are not control's children
at the final, I bring two source codes for state managing components
first of all GraphCollection that extends from StateManagedCollection (both classes was written by me)
using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;
using System.Web.UI;
namespace Farayan.Web.Core
{
public class StateManagedCollection<T> : IList, ICollection, IEnumerable, IEnumerable<T>, IStateManager
where T : class, IStateManager, new()
{
// Fields
private List<T> listItems = new List<T>();
private bool marked = false;
private bool saveAll = false;
// Methods
public void Add(T item)
{
this.listItems.Add(item);
if (this.marked) {
//item.Dirty = true;
}
}
public void AddRange(T[] items)
{
if (items == null) {
throw new ArgumentNullException("items");
}
foreach (T item in items) {
this.Add(item);
}
}
public void Clear()
{
this.listItems.Clear();
if (this.marked) {
this.saveAll = true;
}
}
public bool Contains(T item)
{
return this.listItems.Contains(item);
}
public void CopyTo(Array array, int index)
{
this.listItems.CopyTo(array.Cast<T>().ToArray(), index);
}
public IEnumerator GetEnumerator()
{
return this.listItems.GetEnumerator();
}
public int IndexOf(T item)
{
return this.listItems.IndexOf(item);
}
public void Insert(int index, T item)
{
this.listItems.Insert(index, item);
if (this.marked) {
this.saveAll = true;
}
}
public void LoadViewState(object state)
{
object[] states = state as object[];
if (state == null || states.Length == 0)
return;
for (int i = 0; i < states.Length; i++) {
object itemState = states[i];
if (i < Count) {
T day = (T)listItems[i];
((IStateManager)day).LoadViewState(itemState);
} else {
T day = new T();
((IStateManager)day).LoadViewState(itemState);
listItems.Add(day);
}
}
}
public void Remove(T item)
{
int index = this.IndexOf(item);
if (index >= 0)
this.RemoveAt(index);
}
public void RemoveAt(int index)
{
this.listItems.RemoveAt(index);
if (this.marked) {
this.saveAll = true;
}
}
public object SaveViewState()
{
List<object> state = new List<object>(Count);
foreach (T day in listItems)
state.Add(((IStateManager)day).SaveViewState());
return state.ToArray();
}
int IList.Add(object item)
{
T item2 = (T)item;
this.listItems.Add(item2);
return listItems.Count - 1;
}
bool IList.Contains(object item)
{
return this.Contains((T)item);
}
int IList.IndexOf(object item)
{
return this.IndexOf((T)item);
}
void IList.Insert(int index, object item)
{
this.Insert(index, (T)item);
}
void IList.Remove(object item)
{
this.Remove((T)item);
}
void IStateManager.LoadViewState(object state)
{
this.LoadViewState(state);
}
object IStateManager.SaveViewState()
{
return this.SaveViewState();
}
void IStateManager.TrackViewState()
{
this.TrackViewState();
}
public void TrackViewState()
{
this.marked = true;
for (int i = 0; i < this.Count; i++) {
((IStateManager)this[i]).TrackViewState();
}
}
// Properties
public int Capacity
{
get
{
return this.listItems.Capacity;
}
set
{
this.listItems.Capacity = value;
}
}
public int Count
{
get
{
return this.listItems.Count;
}
}
public bool IsReadOnly
{
get
{
return false;
}
}
public bool IsSynchronized
{
get
{
return false;
}
}
public T this[int index]
{
get
{
return (T)this.listItems[index];
}
}
public object SyncRoot
{
get
{
return this;
}
}
bool IList.IsFixedSize
{
get
{
return false;
}
}
object IList.this[int index]
{
get
{
return this.listItems[index];
}
set
{
this.listItems[index] = (T)value;
}
}
bool IStateManager.IsTrackingViewState
{
get
{
return this.marked;
}
}
#region IEnumerable<T> Members
IEnumerator<T> IEnumerable<T>.GetEnumerator()
{
return this.listItems.GetEnumerator();
}
#endregion
#region IEnumerable Members
IEnumerator IEnumerable.GetEnumerator()
{
return this.GetEnumerator();
}
#endregion
}
}
and GraphCollection
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using Farayan.Web.Core;
namespace Farayan.Web.AmCharts
{
public class GraphCollection : StateManagedCollection<Graph>
{
}
}
and finally Graph in our example:
using System;
using System.Linq;
using System.Collections.ObjectModel;
using System.Drawing;
using System.Web.UI;
using System.ComponentModel;
using Farayan.Web.AmCharts;
using System.Collections.Generic;
using Farayan.Web.Controls;
using System.Runtime;
using Farayan.Web.Core;
namespace Farayan.Web.AmCharts
{
public class Graph : StateManager
{
#region Colorize Property
[Browsable(true)]
[Localizable(false)]
[PersistenceMode(PersistenceMode.Attribute)]
[DefaultValue(false)]
public virtual bool Colorize
{
get { return ViewState["Colorize"] == null ? false : (bool)ViewState["Colorize"]; }
set { ViewState["Colorize"] = value; }
}
#endregion
//==============================
public override void LoadViewState(object state)
{
base.LoadViewState(state);
}
public override object SaveViewState()
{
return base.SaveViewState();
}
}
}
you may noticed that Graph extends StateManager class
using System;
using System.Collections;
using System.Collections.Generic;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Web.UI;
using Farayan.Web.AmCharts;
namespace Farayan.Web.AmCharts
{
public class StateManager : IStateManager
{
protected StateBag ViewState = new StateBag();
#region IStateManager Members
public virtual bool IsTrackingViewState
{
get { return true; }
}
public virtual void LoadViewState(object state)
{
if (state != null) {
ArrayList arrayList = (ArrayList)state;
for (int i = 0; i < arrayList.Count; i += 2) {
string value = ((IndexedString)arrayList[i]).Value;
object value2 = arrayList[i + 1];
ViewState.Add(value, value2);
}
}
}
public virtual object SaveViewState()
{
ArrayList arrayList = new ArrayList();
if (this.ViewState.Count != 0) {
IDictionaryEnumerator enumerator = this.ViewState.GetEnumerator();
while (enumerator.MoveNext()) {
StateItem stateItem = (StateItem)enumerator.Value;
//if (stateItem.IsDirty) {
if (arrayList == null) {
arrayList = new ArrayList();
}
arrayList.Add(new IndexedString((string)enumerator.Key));
arrayList.Add(stateItem.Value);
//}
}
}
return arrayList;
}
public virtual void TrackViewState()
{
}
#endregion
#region IStateManager Members
bool IStateManager.IsTrackingViewState
{
get { return this.IsTrackingViewState; }
}
void IStateManager.LoadViewState(object state)
{
this.LoadViewState(state);
}
object IStateManager.SaveViewState()
{
return this.SaveViewState();
}
void IStateManager.TrackViewState()
{
this.TrackViewState();
}
#endregion
}
}
I have a model with properties that look like this:
public class YourDetails {
[Required(ErrorMessage = "Code is required")]
[StringLength(10, ErrorMessage = "Code length is wrong", MinimumLength = 2)]
[Range(0, int.MaxValue, ErrorMessage = "Please enter a value bigger than {1}")]
public int Code { get; set; }
}
The UI validation is setup the usual out of the box way with unobtrusive JS validation plugin.
The issue: I have 2 navigation actions, back and next. Next is fine, validation fires when things are wrong, and when things are right i.e. .isValid() returns true, the data is passed to the DB service etc etc.
However when I press 'back' I have a requirement to validate the form/ViewModel differently prior to saving. I.e. make sure Code is a positive integer, but don't bother with the Required or StringLength validation.
So basically I want to validate fully on Next but partially on Back. Is that possible?
When I've done something similar in the past the easiest way i found was to use fluent validation http://fluentvalidation.codeplex.com/wikipage?title=mvc. You can pass parameters to the validator and switch to different rule sets.
I've used the following conditional "Required" & "StringLength" attributes in the past and they work well.
Required If Attribute:
using System;
using System.ComponentModel.DataAnnotations;
using System.Reflection;
namespace Website.Core.Mvc.DataAnnotations
{
[AttributeUsage(AttributeTargets.Parameter | AttributeTargets.Field | AttributeTargets.Property, AllowMultiple = true)]
public class RequiredIfAttribute : RequiredAttribute
{
public string OtherProperty { get; set; }
public object OtherPropertyValue { get; set; }
public RequiredIfAttribute(string otherProperty, object value)
: base()
{
OtherProperty = otherProperty;
OtherPropertyValue = value;
}
private object _TypeId = new object();
public override object TypeId
{
get
{
return _TypeId;
}
}
protected override ValidationResult IsValid(object value, ValidationContext validationContext)
{
PropertyInfo property = validationContext.ObjectType.GetProperty(this.OtherProperty);
if (property == null)
{
return new ValidationResult(this.OtherProperty + " not found");
}
// Get
object actualOtherPropertyValue = property.GetValue(validationContext.ObjectInstance, null);
// If the other property matches the expected value then validate as normal
if (IsRequired(OtherPropertyValue, actualOtherPropertyValue))
{
// Call base and validate required as normal
ValidationResult isValid = base.IsValid(value, validationContext);
return isValid;
}
return ValidationResult.Success;
}
protected virtual bool IsRequired(object otherPropertyValue, object actualOtherPropertyValue)
{
return object.Equals(OtherPropertyValue, actualOtherPropertyValue);
}
}
}
String Length If Attribute:
using System.ComponentModel.DataAnnotations;
using System.Reflection;
namespace Website.Core.Mvc.DataAnnotations
{
public class StringLengthIfAttribute : StringLengthAttribute
{
public string OtherProperty { get; set; }
public object OtherPropertyValue { get; set; }
public StringLengthIfAttribute(int maximumLength, string otherProperty, object value)
: base(maximumLength)
{
OtherProperty = otherProperty;
OtherPropertyValue = value;
}
protected override ValidationResult IsValid(object value, ValidationContext validationContext)
{
PropertyInfo property = validationContext.ObjectType.GetProperty(this.OtherProperty);
if (property == null)
{
return new ValidationResult(this.OtherProperty + " not found");
}
// Get
object actualOtherPropertyValue = property.GetValue(validationContext.ObjectInstance, null);
// If the other property matches the expected value then validate as normal
if (object.Equals(OtherPropertyValue, actualOtherPropertyValue))
{
// Call base and validate required as normal
return base.IsValid(value, validationContext);
}
return null;
}
}
}
Example Usage:
public class MyModel
{
[RequiredIf("IsBack", false)]
public string Name { get; set; }
public bool IsBack { get; set; }
}
I am trying to find out how to solve the problem for serializing a type of bool from a camel case string.
I have the following xml
<Root>
<BoolElement>
False
</BoolElement>
</Root>
and the following class
[XmlRoot("Root")]
public class RootObj{
[XmlElement("BoolElement")]
public bool BoolElement{get;set;}
}
this will produce an error.
If I use the same class and rename the "False" to "false" it will work. The problem is that I can't edit the xml.
Does anyone know how can I solve this?
You could use a backing field to aid for the deserialization of this invalid XML (I say invalid because according to the xsd:boolean schema False is an invalid value):
[XmlRoot("Root")]
public class RootObj
{
[XmlElement("BoolElement")]
public string BackingBoolElement
{
set
{
BoolElement = bool.Parse(value.ToLower());
}
get
{
return BoolElement.ToString();
}
}
[XmlIgnore]
public bool BoolElement { get; set; }
}
False is not a valid value for an xsd:boolean (but as you note false and 0 are) - if you cannot change the source data, then you could have a separate property purely for XML serialisation:
[XmlRoot("Root")]
public class RootObj{
[XmlElement("BoolElement")]
public string BoolElementForSerialization
{
get
{
return (this.BoolElement ? "True" : "False");
}
set
{
this.BoolElement = (string.Compare(value, "false", StringComparison.OrdinalIgnoreCase) != 0);
}
}
[XmlIgnore]
public bool BoolElement{get;set;}
}
I created a new Boolean type that can deserialize from any string. It may not be perfect but it suited my needs at the time.
For the class you want to use simply change the data type from bool to SerializableBoolean:
[XmlRoot("Root")]
public class RootObj{
[XmlElement("BoolElement")]
public SerializableBoolean BoolElement{get;set;}
}
You can then use the BoolElement property like any normal bool data type:
RootObj myObj = new RootObj();
if (myObj.BoolElement) { ... }
Here is the code for the SerializableBoolean class, note this code only handles deserializing, serializing to xml wasn't required for my purposes and so not implemented.
[System.Diagnostics.DebuggerDisplay("{Value}")]
public struct SerializableBoolean: System.Xml.Serialization.IXmlSerializable
{
private bool Value { get; set; }
public override bool Equals(object obj)
{
if (obj is string stringBoolean)
{
bool.TryParse(stringBoolean, out bool boolean);
return Value == boolean;
}
else if (obj is bool boolean)
{
return Value == boolean;
}
else if (obj is SerializableBoolean serializableBoolean)
{
return Value == serializableBoolean.Value;
}
else
{
return Value == Convert.ToBoolean(obj);
}
}
public override int GetHashCode()
{
return -1937169414 + Value.GetHashCode();
}
public XmlSchema GetSchema()
{
throw new NotImplementedException();
}
public void ReadXml(XmlReader reader)
{
Value = Convert.ToBoolean(reader.ReadElementContentAsString());
}
public void WriteXml(XmlWriter writer)
{
throw new NotImplementedException();
}
public static bool operator ==(SerializableBoolean obj1, bool obj2)
{
return obj1.Value.Equals(obj2);
}
public static bool operator !=(SerializableBoolean obj1, bool obj2)
{
return !obj1.Value.Equals(obj2);
}
public static implicit operator SerializableBoolean(string value)
{
return new SerializableBoolean() { Value = Convert.ToBoolean(value) };
}
public static implicit operator SerializableBoolean(bool value)
{
return new SerializableBoolean() { Value = value };
}
public static implicit operator bool(SerializableBoolean b)
{
return b.Value;
}
}
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);
}
}