Tuesday, June 24, 2008

Watch Out: Window.ObjectKind is UPPER CASE!

Using Windows2.CreateToolWindow2() to create a VisualStudio addin tool window? If you do, then maybe you want to check how often it is called during the life cycle of your addin. And if you notice that you create it twice, you may want to avoid that by checking the collection EnvDTE80.Windows. If your tool window is already contained you don't want to create a second instance of your tool window. There is a possible surprise, though. Windows2.CreateToolWindow2() expects as the fifth parameter a guid. The online documentation (see here) says it is the "GuidPosition". This is a little misleading since it doesn't really refer to a position. In reality it is the type of the tool window, e.g. the Solution Explorer. Now, when you create the boiler plate code you may just use the example given there. If you do, then change the content of the variable guidpos given in the code to all upper case. So the important bit is the following change:
string guidpos = "{426E8D27-3D33-4fc8-B3E9-9883AADC679F}";
string guidpos = "{426E8D27-3D33-4FC8-B3E9-9883AADC679F}";

I've highlighted the important bit with red color, bold, and a larger font. In addition I have underlined it. I think you got the idea. Why is this change important? Assume you iterate over the collection as follows:
foreach(Window2 toolWin in toolWins) {
string toolWinKind = toolWin.ObjectKind;
if( toolWinKind.Equals(guidString) ) {
 _toolWindow = toolWin;
The Equals() call may always result in 'false' even if you think you are looking at the correct tool window. The reason is that ObjectKind returns the guid all upper case. The example code has two lower case characters in the guidpos variable. The same can also happen when you use "Create GUID" from the "Tools" menu in Visual Studio. It may generate a guid for you with one or more lower case digits ('a' through 'f') as well. It's unfortunate that the online documentation doesn't mention that some time between calling CreateToolWindow2() and calling ObjectKind everything is made upper case. The example code leads to potentially incorrect behavior of your addin as well. This post gives you the heads-up. It took me quite some time to spot this little difference. In my case it was 'f' versus 'F' and only when Equals() insisted on returning false I took a closer look. Maybe this helps you saving some development time. And maybe someone from Microsoft is reading this. I tried to add it as Community Content at MSDN. It wasn't possible. So I rated the article and left a comment adding the suggestions for improvement. This would have been ideal for "Community Content". MSFT, you mind updating the online material? Thank you!


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