Shows how to add custom UIContexts

VSIX UIContext

On the package

    [ProvideAutoLoad(UIContexts.LoadContext)]
    [ProvideUIContextRule(UIContexts.LoadContext,
        "RightFileTypeOpen",
        "(CSharpFileOpen | VBFileOpen)",
        new[] { "CSharpFileOpen", "VBFileOpen" },
        new[] { "ActiveEditorContentType:CSharp", "ActiveEditorContentType:Basic" })]

In the VSCT

  <VisibilityConstraints>
    <VisibilityItem guid="guidCmdSet" id="cmdidStuff" context=" guidLoadContext " />
  </VisibilityConstraints>

 <Symbols>
   <GuidSymbol name="guidLoadContext" value="{C6216099-CA25-4821-A541-044E82B4DCF1}" />
 </Symbols>


As a helper containing the GUIDs

namespace Foo
{
    internal static class UIContexts
    {
        public const string LoadContext = "C6216099-CA25-4821-A541-044E82B4DCF1";
    }
}

Bolded GUIDs must match

Docs on allowed conditions: https://msdn.microsoft.com/en-us/library/mt750411.aspx

What else can be used for ActiveEditorContentType, other than CSharp and Basic?

I think finding the limitations of this term type is "trial and error", but I was able to detect JSON with "ActiveEditorContentType:Json"