ASP.NET AJAX Library: When they say exact signature, they mean EXACT SIGNATURE

Here is a little gotcha to look out for when using ASP.NET AJAX Library controls, such as the AutoComplete control. For any control that makes a call to a web service, the web service must have the EXACT signature listed for the the point that even the parameter names and case of said parameter names must match EXACTLY. This tripped me up, as my controls were not calling my web service (with no error message or feedback as well) because I called the first parameter "String prefix" instead of "String prefixText".

I will concede that Microsoft does state this information in the online documentation (, but I find it difficult to locate because it is a single non-descriptive line under the code sample box. I think something like that should have a Tip/Remember/Warning icon next to it or something, a la the Dummies series of books.

I can understand why this is necessary given the nature of JSON, which the controls use behind the scenes, but I think it still warrants a warning or potentially some kind of indication that the Web Service call could not be made.