MethodBuilder.DefineGenericParameters Method
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Sets the number of generic type parameters for the current method, specifies their names, and returns an array of GenericTypeParameterBuilder objects that can be used to define their constraints.
Namespace: System.Reflection.Emit
Assembly: mscorlib (in mscorlib.dll)
Syntax
'Declaration
Public Function DefineGenericParameters ( _
ParamArray names As String() _
) As GenericTypeParameterBuilder()
public GenericTypeParameterBuilder[] DefineGenericParameters(
params string[] names
)
Parameters
- names
Type: array<System.String[]
An array of strings that represent the names of the generic type parameters.
Return Value
Type: array<System.Reflection.Emit.GenericTypeParameterBuilder[]
An array of GenericTypeParameterBuilder objects representing the type parameters of the generic method.
Exceptions
| Exception | Condition |
|---|---|
| InvalidOperationException | Generic type parameters have already been defined for this method. -or- The method has been completed already. -or- The SetImplementationFlags method has been called for the current method. |
| ArgumentNullException | names is nulla null reference (Nothing in Visual Basic). -or- An element of names is nulla null reference (Nothing in Visual Basic). |
| ArgumentException | names is an empty array. |
Remarks
Calling the DefineGenericParameters method makes the current method generic. There is no way to undo this change. Calling this method a second time causes an InvalidOperationException.
The type parameters of the generic method can be retrieved later by using the GetGenericArguments method.
By convention, a type parameter name is a single uppercase letter.
For more information, see MethodInfo.IsGenericMethod and MethodInfo.GetGenericMethodDefinition. For information on generic types, see Type.IsGenericType.
Examples
The following example creates a dynamic type, DemoType, which contains the dynamic generic method DemoMethod. This method has two generic type parameters, one of which is used as a parameter and the other as the return type.
.gif "Note") Note: |
|---|
This code example generates a simple method body that merely returns a null reference. For a code example with a more fully developed method body that creates and uses generic types, see How to: Define a Generic Method with Reflection Emit. |
Imports System.Reflection
Imports System.Reflection.Emit
Class Example
Public Shared Sub Demo(ByVal outputBlock As System.Windows.Controls.TextBlock)
' Creating a dynamic assembly requires an AssemblyName
' object, and the current application domain.
'
Dim asmName As New AssemblyName("Example1")
Dim domain As AppDomain = AppDomain.CurrentDomain
Dim demoAssembly As AssemblyBuilder = _
domain.DefineDynamicAssembly(asmName, _
AssemblyBuilderAccess.Run)
Dim demoModule As ModuleBuilder = _
demoAssembly.DefineDynamicModule( _
asmName.Name)
Dim demoType As TypeBuilder = demoModule.DefineType( _
"DemoType", _
TypeAttributes.Public Or TypeAttributes.Abstract)
' Define a Shared, Public method with standard calling
' conventions. Do not specify the parameter types or the
' return type, because type parameters will be used for
' those types, and the type parameters have not been
' defined yet.
Dim demoMethod As MethodBuilder = _
demoType.DefineMethod("DemoMethod", _
MethodAttributes.Public Or MethodAttributes.Static)
' Defining generic parameters for the method makes it a
' generic method. By convention, type parameters are
' single alphabetic characters. T and U are used here.
'
Dim typeParamNames() As String = {"T", "U"}
Dim typeParameters() As GenericTypeParameterBuilder = _
demoMethod.DefineGenericParameters(typeParamNames)
' The second type parameter is constrained to be a
' reference type.
typeParameters(1).SetGenericParameterAttributes( _
GenericParameterAttributes.ReferenceTypeConstraint)
' Use the IsGenericMethod property to find out if a
' dynamic method is generic, and IsGenericMethodDefinition
' to find out if it defines a generic method.
outputBlock.Text &= String.Format("Is DemoMethod generic? {0}", _
demoMethod.IsGenericMethod) & vbCrLf
outputBlock.Text &= String.Format("Is DemoMethod a generic method definition? {0}", _
demoMethod.IsGenericMethodDefinition) & vbCrLf
' Set parameter types for the method. The method takes
' one parameter, and its type is specified by the first
' type parameter, T.
Dim params() As Type = {typeParameters(0)}
demoMethod.SetParameters(params)
' Set the return type for the method. The return type is
' specified by the second type parameter, U.
demoMethod.SetReturnType(typeParameters(1))
' Generate a code body for the method. The method doesn't
' do anything except return Nothing.
'
Dim ilgen As ILGenerator = demoMethod.GetILGenerator()
ilgen.Emit(OpCodes.Ldnull)
ilgen.Emit(OpCodes.Ret)
' Complete the type.
Dim dt As Type = demoType.CreateType()
' To bind types to a dynamic generic method, you must
' first call the GetMethod method on the completed type.
' You can then define an array of types, and bind them
' to the method.
Dim m As MethodInfo = dt.GetMethod("DemoMethod")
Dim typeArgs() As Type = _
{GetType(String), GetType(Example)}
Dim bound As MethodInfo = m.MakeGenericMethod(typeArgs)
' Display a string representing the bound method.
outputBlock.Text &= bound.ToString() & vbCrLf
End Sub
End Class
' This code example produces the following output:
'Is DemoMethod generic? True
'Is DemoMethod a generic method definition? True
'DemoMethodBuilder DemoMethod[String,DemoMethodBuilder](System.String)
using System;
using System.Reflection;
using System.Reflection.Emit;
class Example
{
public static void Demo(System.Windows.Controls.TextBlock outputBlock)
{
// Creating a dynamic assembly requires an AssemblyName
// object, and the current application domain.
//
AssemblyName asmName =
new AssemblyName("Example1");
AppDomain domain = AppDomain.CurrentDomain;
AssemblyBuilder demoAssembly =
domain.DefineDynamicAssembly(
asmName,
AssemblyBuilderAccess.Run
);
ModuleBuilder demoModule =
demoAssembly.DefineDynamicModule(
asmName.Name
);
TypeBuilder demoType = demoModule.DefineType(
"DemoType",
TypeAttributes.Public | TypeAttributes.Abstract
);
// Define a Shared, Public method with standard calling
// conventions. Do not specify the parameter types or the
// return type, because type parameters will be used for
// those types, and the type parameters have not been
// defined yet.
MethodBuilder demoMethod = demoType.DefineMethod(
"DemoMethod",
MethodAttributes.Public | MethodAttributes.Static
);
// Defining generic parameters for the method makes it a
// generic method. By convention, type parameters are
// single alphabetic characters. T and U are used here.
//
string[] typeParamNames = { "T", "U" };
GenericTypeParameterBuilder[] typeParameters =
demoMethod.DefineGenericParameters(typeParamNames);
// The second type parameter is constrained to be a
// reference type.
typeParameters[1].SetGenericParameterAttributes(
GenericParameterAttributes.ReferenceTypeConstraint);
// Use the IsGenericMethod property to find out if a
// dynamic method is generic, and IsGenericMethodDefinition
// to find out if it defines a generic method.
outputBlock.Text += String.Format("Is DemoMethod generic? {0}",
demoMethod.IsGenericMethod) + "\n";
outputBlock.Text += String.Format("Is DemoMethod a generic method definition? {0}",
demoMethod.IsGenericMethodDefinition) + "\n";
// Set parameter types for the method. The method takes
// one parameter, and its type is specified by the first
// type parameter, T.
Type[] parms = { typeParameters[0] };
demoMethod.SetParameters(parms);
// Set the return type for the method. The return type is
// specified by the second type parameter, U.
demoMethod.SetReturnType(typeParameters[1]);
// Generate a code body for the method. The method doesn't
// do anything except return null.
//
ILGenerator ilgen = demoMethod.GetILGenerator();
ilgen.Emit(OpCodes.Ldnull);
ilgen.Emit(OpCodes.Ret);
// Complete the type.
Type dt = demoType.CreateType();
// To bind types to a dynamic generic method, you must
// first call the GetMethod method on the completed type.
// You can then define an array of types, and bind them
// to the method.
MethodInfo m = dt.GetMethod("DemoMethod");
Type[] typeArgs = { typeof(string), typeof(Example) };
MethodInfo bound = m.MakeGenericMethod(typeArgs);
// Display a string representing the bound method.
outputBlock.Text += bound.ToString() + "\n";
}
}
/* This code example produces the following output:
Is DemoMethod generic? True
Is DemoMethod a generic method definition? True
DemoMethodBuilder DemoMethod[String,DemoMethodBuilder](System.String)
*/
Version Information
Silverlight
Supported in: 5, 4, 3
Platforms
For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.