Leak in RuntimeBinder when using "dynamic" keyword with __ComObject

Question

Does anybody know if there is a way of preventing a memory leak in RuntimeBinder when using "dynamic" keyword with __ComObject instances in C#?

I got the following code:

var t = Type.GetTypeFromCLSID(new Guid("BB06C0E4-D293-4f75-8A90-CB05B6477EEE"));
while (true)
{
    dynamic o = System.Activator.CreateInstance(t);
    Marshal.ReleaseComObject(o);
}

This leaks LocalVariableSymbol class instances (and other from the Microsoft.CSharp.RuntimeBinder.Semantics namespace).

Replacing "dynamic" with "object" i.e.:

    object o = System.Activator.CreateInstance(t);

fixes the leak but I'd prefer to keep using dynamic (the actual code is much more complex and makes use of "dynamic").

I know the RuntimeBinder singleton caches the data and this causes the leak but do you know if there's any way to cleanup the cache etc.?

Many thanks!

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Similar questions:

• Memory Overflow: Having an increasing number of Microsoft.CSharp.RuntimeBinder.Semantics
• Memory leak in CLR classes

Related links:

• https://connect.microsoft.com/VisualStudio/feedback/details/1925659 (retired by Microsoft)
• https://github.com/dotnet/roslyn/issues/2887

Answer 1

The solution in my case was to replace:

dynamic o = System.Activator.CreateInstance(t);

with:

object o = System.Activator.CreateInstance(t);
dynamic d = o;

The memory leak no longer occurs having the workaround applied.