PIDTemplate in Wix

I am working on an installer written in WIX. It defines PIDTemplate as

<Property Id="PIDTemplate"><![CDATA[{50}<????????-????????-??????????>]]></Property>

The code worked - asking 28 letters and digits, including two hyphens.

However, Microsoft documentation http://msdn.microsoft.com/en-us/library/aa369797%28v=vs.85%29.aspx does not mention {50}. What is this used for?

Also the page on MSDN site is quite difficult to understand. It says:

The alternate digit, %, and alternate alphanumeric characters, ^, ?, and ` fields allow custom actions to differentiate between fields in a way that can be c开发者_JS百科ontrolled by the mask, for example, ^ can be used for fields that should be uppercase.

My PIDKey allows only uppercase letters and digits. Does that meant that I can achieve it by replacing ? with ^?

However, Microsoft documentation http://msdn.microsoft.com/en-us/library/aa369797%28v=vs.85%29.aspx does not mention {50}. What is this used for?

It specifies the maximum length of the edit (50 characters).

My PIDKey allows only uppercase letters and digits. Does that meant that I can achieve it by replacing ? with ^?

? means digit or character. I'm not sure if ^ supports digits, but you can try using it instead of ?. And to answer your question, yes, it should limit the edit to uppercase characters.