Show Visualizers Error “could not load this custom viewer”

Question

When I try to inspect DataSet by standard DataSet visualizer I see this error \"could not load this custom viewer\". I wrote simple dataset visualizer, but

Answer 1

Clearing Visual Studio Cache fixed it for me.

Just follow these basic steps:

Step 1: clear the Component Cache

1. Close Visual Studio (ensure devenv.exe is not present in the Task Manager)
2. Delete the directory:

%USERPROFILE%\AppData\Local\Microsoft\VisualStudio\14.0\ComponentModelCache

If step 1 doesn't work then

Step 2: cleanup your user’s temp folder. Delete this directory:

%USERPROFILE%\AppData\Local\Temp

If step 2 doesn't work then

Step 3: Delete all these directories:

%USERPROFILE%\AppData\Local\Microsoft\Team Foundation

%USERPROFILE%\AppData\Local\Microsoft\VisualStudio

%USERPROFILE%\AppData\Local\Microsoft\VSCommon

Credit : https://errorhandlinginskills.wordpress.com/2018/07/28/how-to-clear-visual-studio-cache/

Answer 2

The best way to diagnose this is to debug Visual Studio itself. Try the following

• Get Visual Studio into the state where you want to use your Visualizer
• Attach another version of Visual Studio to the original one (managed only)
• Disable Just My Code (Tools -> Options -> Debugger -> uncheck "Just my Code")
• Go to Debug -> Exceptions
• Check the Throw box for "CLR Exceptions"
• Switch back to the first VS and Attempt to show your Visualizer

This should throw an exception which will then show up in the second instance of Visual Studio. Please post back with this information if it's not enough to solve your problem.

Answer 3

I had the same issue in VS 2015 and none of the answers here helped me but I found an issue on github that described my problem.

The solution, or workaround might be more accurate, for me was to turn off the option "Use the legacy C# and VB evaluators" that I (apparently) had turned on in Tools -> Options -> Debugging -> General.

Answer 4

I found the cause of this error. According this advice http://go.microsoft.com/fwlink/?LinkID=155570 I add to devenv.exe.config this parameter NetFx40_LegacySecurityPolicy enabled="true" and with this parameter in .config file I have the error when try to open DataSet visualizer.

When I remove this parameter all became ok. Execption "The security state of an AppDomain was modified by an AppDomainManager configured with the NoSecurityChanges flag" fixed too.

But I NEED NetFx40_LegacySecurityPolicy enabled="true" parameter to work with old projects.

Answer 5

For me. Visual Studio 2010 restart helped.