What type is “new { id = 0 }” in C#?

Question

I'm using var abc = new { id = 0 }; in my C# code without knowing what type it exactly is!

Is is simply called an object? Is it a particular type of object?

I want to know coz I don't know how to add fields to this kind of object

Quick example: I have var abc = new { id = 0 }; and I want to add to abc the field name = "david"

Answer 1

It is an anonymous type , that is, it does not have a type that you can use in code (though the compiler generates one).

MSDN says:

The type name is generated by the compiler and is not available at the source code level.

If you want to add a property, you can simply do so:

var abc = new { id = 0, name = "david" };

Answer 2

It creates anonymous class object with one field called id . Look on msdn for details. Once you create object it cannot be extended .

This what this class looks like when open with .net Reflector

[CompilerGenerated, DebuggerDisplay(@"\{ id = {id} }", Type="<Anonymous Type>")]
internal sealed class <>f__AnonymousType0<<id>j__TPar>
{
    // Fields
   [DebuggerBrowsable(DebuggerBrowsableState.Never)]
   private readonly <id>j__TPar <id>i__Field;

   // Methods
   [DebuggerHidden]
   public <>f__AnonymousType0(<id>j__TPar id);

   [DebuggerHidden]
   public override bool Equals(object value);

   [DebuggerHidden]
   public override int GetHashCode();

   [DebuggerHidden]
   public override string ToString();

   // Properties
  public <id>j__TPar id { get; }
}

So its compiled to regular class the basic difference is that it cannot be used outside of method scope.