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TypeBuilder.DefineProperty Method (String, PropertyAttributes, Type, Type[])

Adds a new property to the type, with the given name and property signature.

Namespace:  System.Reflection.Emit
Assembly:  mscorlib (in mscorlib.dll)

public PropertyBuilder DefineProperty(
	string name,
	PropertyAttributes attributes,
	Type returnType,
	Type[] parameterTypes
)

Parameters

name
Type: System.String

The name of the property. name cannot contain embedded nulls.

attributes
Type: System.Reflection.PropertyAttributes

The attributes of the property.

returnType
Type: System.Type

The return type of the property.

parameterTypes
Type: System.Type[]

The types of the parameters of the property.

Return Value

Type: System.Reflection.Emit.PropertyBuilder
The defined property.

ExceptionCondition
ArgumentException

The length of name is zero.

ArgumentNullException

name is null.

-or-

Any of the elements of the parameterTypes array is null.

InvalidOperationException

The type was previously created using CreateType.

The following code sample demonstrates how to define a dynamic property and obtain a PropertyBuilder for specification. Note that a PropertyBuilder must also have a corresponding MethodBuilder, which will house the IL logic for the property.


using System;
using System.Threading;
using System.Reflection;
using System.Reflection.Emit;

class PropertyBuilderDemo

{

   public static Type BuildDynamicTypeWithProperties() 
   {
        AppDomain myDomain = Thread.GetDomain();
        AssemblyName myAsmName = new AssemblyName();
        myAsmName.Name = "MyDynamicAssembly";

        // To generate a persistable assembly, specify AssemblyBuilderAccess.RunAndSave.
        AssemblyBuilder myAsmBuilder = myDomain.DefineDynamicAssembly(myAsmName,
                                                        AssemblyBuilderAccess.RunAndSave);
        // Generate a persistable single-module assembly.
        ModuleBuilder myModBuilder = 
            myAsmBuilder.DefineDynamicModule(myAsmName.Name, myAsmName.Name + ".dll");

        TypeBuilder myTypeBuilder = myModBuilder.DefineType("CustomerData", 
                                                        TypeAttributes.Public);

        FieldBuilder customerNameBldr = myTypeBuilder.DefineField("customerName",
                                                        typeof(string),
                                                        FieldAttributes.Private);

        // The last argument of DefineProperty is null, because the 
        // property has no parameters. (If you don't specify null, you must 
        // specify an array of Type objects. For a parameterless property, 
        // use an array with no elements: new Type[] {})
        PropertyBuilder custNamePropBldr = myTypeBuilder.DefineProperty("CustomerName",
                                                         PropertyAttributes.HasDefault,
                                                         typeof(string),
                                                         null);

        // The property set and property get methods require a special 
        // set of attributes.
        MethodAttributes getSetAttr = 
            MethodAttributes.Public | MethodAttributes.SpecialName |
                MethodAttributes.HideBySig;

        // Define the "get" accessor method for CustomerName.
        MethodBuilder custNameGetPropMthdBldr = 
            myTypeBuilder.DefineMethod("get_CustomerName",
                                       getSetAttr,        
                                       typeof(string),
                                       Type.EmptyTypes);

        ILGenerator custNameGetIL = custNameGetPropMthdBldr.GetILGenerator();

        custNameGetIL.Emit(OpCodes.Ldarg_0);
        custNameGetIL.Emit(OpCodes.Ldfld, customerNameBldr);
        custNameGetIL.Emit(OpCodes.Ret);

        // Define the "set" accessor method for CustomerName.
        MethodBuilder custNameSetPropMthdBldr = 
            myTypeBuilder.DefineMethod("set_CustomerName",
                                       getSetAttr,     
                                       null,
                                       new Type[] { typeof(string) });

        ILGenerator custNameSetIL = custNameSetPropMthdBldr.GetILGenerator();

        custNameSetIL.Emit(OpCodes.Ldarg_0);
        custNameSetIL.Emit(OpCodes.Ldarg_1);
        custNameSetIL.Emit(OpCodes.Stfld, customerNameBldr);
        custNameSetIL.Emit(OpCodes.Ret);

        // Last, we must map the two methods created above to our PropertyBuilder to  
        // their corresponding behaviors, "get" and "set" respectively. 
        custNamePropBldr.SetGetMethod(custNameGetPropMthdBldr);
        custNamePropBldr.SetSetMethod(custNameSetPropMthdBldr);


        Type retval = myTypeBuilder.CreateType();

        // Save the assembly so it can be examined with Ildasm.exe, 
        // or referenced by a test program.
        myAsmBuilder.Save(myAsmName.Name + ".dll");
        return retval;
   }

   public static void Main() 
   {
        Type custDataType = BuildDynamicTypeWithProperties();

        PropertyInfo[] custDataPropInfo = custDataType.GetProperties();
        foreach (PropertyInfo pInfo in custDataPropInfo) {
           Console.WriteLine("Property '{0}' created!", pInfo.ToString());
        }

        Console.WriteLine("---");
        // Note that when invoking a property, you need to use the proper BindingFlags - 
        // BindingFlags.SetProperty when you invoke the "set" behavior, and 
        // BindingFlags.GetProperty when you invoke the "get" behavior. Also note that
        // we invoke them based on the name we gave the property, as expected, and not 
        // the name of the methods we bound to the specific property behaviors. 

        object custData = Activator.CreateInstance(custDataType);
        custDataType.InvokeMember("CustomerName", BindingFlags.SetProperty,
                                      null, custData, new object[]{ "Joe User" });

        Console.WriteLine("The customerName field of instance custData has been set to '{0}'.",
                           custDataType.InvokeMember("CustomerName", BindingFlags.GetProperty,
                                                      null, custData, new object[]{ }));
   }

}

// --- O U T P U T --- 
// The output should be as follows: 
// ------------------- 
// Property 'System.String CustomerName [System.String]' created! 
// --- 
// The customerName field of instance custData has been set to 'Joe User'. 
// -------------------

.NET Framework

Supported in: 4.5, 4, 3.5, 3.0, 2.0, 1.1, 1.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

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