Source: Microsoft Support

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Debugging managed code that contains a lot of dynamically created types.

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High memory usage accompanied by high cpu usage.

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High Memory Usage:
The Visual Studio debugger makes a copy of meta-data every time a managed dynamic type is created, even when it already has a previous copy of the same type cached.  This is because there may still be outstanding references to the old copy.  So, when re-creating dynamic types, not only does the debugger make a copy of meta-data for itself to use, it may also create what amouts to a duplicate copy.

High CPU:
This particular pattern of memory usage can also lead to fragmented native heaps in the process.  As the debugging activity progresses, native heaps can become more and more fragmented, causing high cpu usage as it becomes more and more difficult to free continguous space.

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This behavior is considered by design. 

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The only known workaround is to detach the debugger periodically and re-attach.  When the debugger is detached, the copies of metadata are freed.

Othewise, be sure you are caching dynamic types such that you don't re-create them, resulting in multiple copies of metadata for the same type. 

Also, try to limit the number of dynamic types used; try to consolidate functionality in as few dynamic types as reasonably possible.

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