TypeBuilder::GetField Method (Type, FieldInfo)
Returns the field of the specified constructed generic type that corresponds to the specified field of the generic type definition.
Assembly: mscorlib (in mscorlib.dll)
- Type: System::Type
The constructed generic type whose field is returned.
- Type: System.Reflection::FieldInfo
A field on the generic type definition of type, which specifies which field of type to return.
For example, suppose you have a TypeBuilder object that represents the type G<T> in C# syntax (G(Of T) in Visual Basic, generic <T> ref class G in C++) and a FieldBuilder object that represents a field public T F in C# syntax (Public F As T in Visual Basic, public: T F in C++) that is defined by G<T>. Suppose that G<T> has a generic method with type parameter U that creates an instance of the constructed type G<U> and calls field F on that instance. In order to emit the function call, you need a FieldInfo object that represents F on the constructed type — in other words, that is of type U rather than type T. To do this, first call the MakeGenericType method on the TypeBuilder object, specifying the GenericTypeParameterBuilder object that represents U as the type argument. Then call the GetField method with the return value of the MakeGenericType method as parameter type and the FieldBuilder object that represents F as parameter field. The return value is the FieldInfo object you need to emit the function call. The code example demonstrates this scenario.
The following code example contains source code for a generic class named Sample that has a type parameter named T. The class has a field named Field, of type T, and a generic method named GM with its own type parameter, named U. Method GM creates an instance of Sample, substituting its own type parameter U for the type parameter of Sample, and stores its input parameter in Field. This source code is compiled but not used; you can view it with the Ildasm.exe (MSIL Disassembler) and compare it to the code emitted by class Example.
The code in class Example demonstrates the use of the GetField method to emit generic code. The Main method of class Example creates a dynamic assembly containing a class named Sample, and uses the DefineGenericParameters method to make it generic by adding a type parameter named T. A default constructor and a field named Field, of type T, are added to class Sample. A method GM is added and turned into a generic method by using the MethodBuilder::DefineGenericParameters method. The type parameter of GM is named U. After the type parameter is defined, the signature of GM is added by using the MethodBuilder::SetSignature method. There is no return type and no required or custom modifiers, so all the parameters of this method are nullptr except parameterTypes; parameterTypes sets the type of the method's only parameter to U, the method's generic type parameter. The body of the method creates an instance of the constructed type Sample<U> (Sample(Of U) in Visual Basic), assigns the method's parameter to Field, and then prints the value of Field. The GetField method is used to create a FieldInfo that represents the field of the constructed generic type Sample<U> in the OpCodes::Stfld and OpCodes::Ldfld instructions.
A dummy type is defined to hold the entry-point method Main. In the body of Main, the static GM method is invoked on the constructed generic type Sample<int> (Sample(Of Integer) in Visual Basic), with type String substituted for U.
When the code example is run, it saves the emitted assembly as TypeBuilderGetFieldExample.exe. You can run TypeBuilderGetFieldExample.exe, and you can use the Ildasm.exe (MSIL Disassembler) to compare the emitted code with the code for the Sample class that is compiled into the code example itself.
Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2
The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.