“has Stopped working” message after IL Assembly editing

[gavoham]

I am using "dnSpy" application to read and change .net assembly exe module, I chose "Edit IL Instructions..." like that

Then I change "brtrue" to "brfalse" as this picture

Then I saved a module like that

Then I run NGRN like that

Now When I test the exe application I face "Stopped Working" message as soon as I open it

Please help
Thanks a lot