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MethodImplOptions Enum


Specifies constants that define the details of how a method is implemented.

This enumeration supports a bitwise combination of its member values.

public enum class MethodImplOptions
public enum MethodImplOptions
public enum MethodImplOptions
public enum MethodImplOptions
type MethodImplOptions = 
type MethodImplOptions = 
type MethodImplOptions = 
Public Enum MethodImplOptions


AggressiveInlining 256

The method should be inlined if possible.

Unnecessary use of this attribute can reduce performance. The attribute might cause implementation limits to be encountered that will result in slower generated code. Always measure performance to ensure it's helpful to apply this attribute.

AggressiveOptimization 512

The method contains code that should always be optimized for performance.

It's rarely appropriate to use this attribute. Methods that apply this attribute bypass the first tier of tiered compilation and therefore don't benefit from optimizations that rely on tiered compilation. Those optimizations include dynamic PGO and optimizations based on initialized classes. Use of this attribute might also increase memory use. Always measure performance to ensure it's helpful to apply this attribute.

ForwardRef 16

The method is declared, but its implementation is provided elsewhere.

InternalCall 4096

The call is internal, that is, it calls a method that's implemented within the common language runtime.

NoInlining 8

The method cannot be inlined. Inlining is an optimization by which a method call is replaced with the method body.

NoOptimization 64

The method is not optimized by the just-in-time (JIT) compiler or by native code generation (see Ngen.exe) when debugging possible code generation problems.

PreserveSig 128

The method signature is exported exactly as declared.

SecurityMitigations 1024

This member is reserved for future use. It was introduced in .NET Framework 4.8.

Synchronized 32

The method can be executed by only one thread at a time. Static methods lock on the type, whereas instance methods lock on the instance. Only one thread can execute in any of the instance functions, and only one thread can execute in any of a class's static functions.

Unmanaged 4

The method is implemented in unmanaged code.


This enumeration is used with the MethodImplAttribute attribute.

You can specify multiple MethodImplOptions values by using the bitwise OR operator.


Locking on the instance or on the type, as with 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 or other synchronization problems.

Applies to