Exceptions in Windows PowerShell, other dynamic languages, and dynamically executed C# code when code that targets the .NET Framework calls some methods

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Symptoms

When code that targets the Microsoft .NET Framework 4.5.1 or the Microsoft .NET Framework 4.5.2, and the code dynamically binds to methods (for example, using a script in Windows PowerShell, IronPython, IronRuby, or another dynamic language) calls the System.Runtime.InteropServices.Marshal.SizeOf method or the System.Runtime.InteropServices.Marshal.PtrToStructure method, you may experience the following issues.

Note Code that is already compiled into a managed executable does not exhibit these issues, unless that code uses the dynamic keyword in C#.

Issue 1

Calls to System.Runtime.InteropServices.Marshal.SizeOf throw the following MethodInvocationException exception:

Type '<Type name>' cannot be marshalled as an unmanaged structure; no meaningful size or offset can be computed.

Issue 2

Calls to System.Runtime.InteropServices.Marshal.PtrToStructure throw the following MethodInvocationException exception:

The specified structure must be blittable or have layout information.

Issue 3

Calls to System.Runtime.InteropServices.Marshal.PtrToStructure throw the following RuntimeBinderException exception:

Cannot implicitly convert type 'void' to 'object'.

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Cause

This issue occurs because scripting engines and dynamic languages may bind to a new overload that is introduced in the .NET Framework. Specifically, calls that formerly used Marshal.SizeOf(Type) may now call Marshal.SizeOf<T>(T), and calls that used Marshal.PtrToStructure(IntPtr, Type) may now call Marshal.PtrToStructure<T>(IntPtr, T). This change causes the methods or the runtime binder to throw an exception.

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Workaround

To work around this issue, change the code so that it uses the correct overload if your language enables you to do this. If you cannot specify a specific method overload, change the code so that it uses the new method overload correctly instead.

For C# Dynamic Invocation

Add a cast to System.Type within the call to method SizeOf or method PtrToStructure. For example:

object obj = System.Runtime.InteropServices.Marshal.PtrToStructure(ptr, (System.Type)type);
int size = System.Runtime.InteropServices.Marshal.SizeOf((System.Type)type);

Note This is only necessary when one of the arguments to the method is dynamic.

For Windows PowerShell scripts

Add a cast to System.Type within the call to method SizeOf or method PtrToStructure. For example:

$size = [System.Runtime.InteropServices.Marshal]::SizeOf([System.Type] $type)

$obj = [System.Runtime.InteropServices.Marshal]::PtrToStructure($ptr, [System.Type] $type)

For IronPython scripts

Create a new type instance of the type, and then use the new method overload. For example:

typeInstance = type()

size = System.Runtime.InteropServices.Marshal.SizeOf(typeInstance)

obj = System.Runtime.InteropServices.Marshal.PtrToStructure(ptr, typeInstance)

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