Prevent Visual Studio from trying to load symbols for a particular DLL

Also check that you have no "_NT_SYMBOL_PATH" environment variable. If you have this var symbols will load regardless of VS settings.

In my case it was because I had set "Enable .Net Source Stepping" to true in

Tools > Options > Debugging > General. 

Rather than setting it to false, I set "Enable Just My Code" to true which automatically set "Enable .Net Source Stepping" to false. It gave me a warning before doing so:

Enabling Just my code automatically disabled .Net framework source stepping

Which suggests Just My Code and .Net source stepping are mutually exclusive.

I hope this helps someone.

You can't do this in a very fine grained fashion but you can disable automatic symbol loading and then manually choose the symbols to load via the Modules window (Debug -> Windows -> Modules).

To Disable Automatic Symbol loading

• Tools -> Options -> Debugging -> Symbols
• Check "Search the above locations only when symbols are loaded manually"

From Visual Studio 2010 onwards, you can go to:

Tools -> Options -> Debugging -> Symbols -> Specify excluded modules

and enter the list of the dlls which take too long to load. I use the full path, given by the Output Window; maybe it accepts wildcards or simple file names.