MethodImplAttributes Enumeration
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MethodImplAttributes Enumeration

[ This article is for Windows Phone 8 developers. If you’re developing for Windows 10, see the latest documentation. ]

Specifies flags for the attributes of a method implementation.

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

public enum MethodImplAttributes

Member nameDescription
AggressiveInliningSpecifies that the method should be inlined wherever possible.
CodeTypeMaskSpecifies flags about code type.
ForwardRefSpecifies that the method is not defined.
ILSpecifies that the method implementation is in Microsoft intermediate language (MSIL).
InternalCallSpecifies an internal call.
ManagedSpecifies that the method implementation is managed.
ManagedMaskSpecifies whether the code is managed or unmanaged.
MaxMethodImplValSpecifies a range check value.
NativeSpecifies that the method implementation is native.
NoInliningSpecifies that the method cannot be inlined.
NoOptimizationSpecifies that the method is not optimized by the just-in-time (JIT) compiler when debugging possible code generation problems.
OPTILSpecifies that the method implementation is in optimized intermediate language (OPTIL).
PreserveSigSpecifies that the method signature is exported exactly as declared.
RuntimeSpecifies that the method implementation is provided by the runtime.
SynchronizedSpecifies that the method is single-threaded through the body. Static methods (Shared methods in Visual Basic) lock on the type, whereas instance methods lock on the instance. You can also use the C# lock statement or the Visual Basic Lock function for this purpose.
UnmanagedSpecifies that the method implementation is unmanaged.

The attributes are combined using the bitwise OR operation.

Code implementation masks:

  • CodeTypeMask

  • IL

  • Native


  • Runtime

Managed masks:

  • ManagedMask

  • Managed

  • Unmanaged

Implementation information and interop masks:

  • AggressiveInlining

  • ForwardRef

  • InternalCall

  • MaxMethodImplVal

  • NoInlining

  • NoOptimization

  • PreserveSig

  • Synchronized


Locking on the instance or on the type, for example, by using the Synchronized flag, is not recommended for public types because code other than your own can take locks on public types and instances. This might cause deadlocks.

Windows Phone OS

Supported in: 8.1, 8.0, 7.1, 7.0

Windows Phone

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