Castclass Field
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OpCodes.Castclass Field

Attempts to cast an object passed by reference to the specified class.

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

'Declaration
<ComVisibleAttribute(True)> _
Public Shared ReadOnly Castclass As OpCode

The following table lists the instruction's hexadecimal and Microsoft intermediate language (MSIL) assembly format, along with a brief reference summary:

Format

Assembly Format

Description

74 < T >

castclass class

Casts an object to a new object of type class.

The stack transitional behavior, in sequential order, is:

  1. An object reference is pushed onto the stack.

  2. The object reference is popped from the stack; the referenced object is cast as the specified class.

  3. If successful, a new object reference is pushed onto the stack.

The castclass instruction attempts to cast the object reference (type O) atop the stack to a specified class. The new class is specified by a metadata token indicating the desired class. If the class of the object on the top of the stack does not implement the new class (assuming the new class is an interface) and is not a derived class of the new class then an InvalidCastException is thrown. If the object reference is a null reference, castclass succeeds and returns the new object as a null reference.

InvalidCastException is thrown if obj cannot be cast to class.

TypeLoadException is thrown if class cannot be found. This is typically detected when MSIL instructions are converted to native code, not at run time.

The following Emit method overload can use the castclass opcode:

  • ILGenerator.Emit(OpCode, Type)

Silverlight

Supported in: 5, 4, 3

Silverlight for Windows Phone

Supported in: Windows Phone OS 7.1

For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.

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