Include only certain file types when searching in Visual Studio

In the Find in Files dialog (Ctrl+Shift+F), there should be a field called Find Options. You should be able to enter the extensions of fields you want to search in a field in this dialog:

*.cs; *.aspx; *.ascx; 

You can choose file types from default or type your own. Regular expressions available for complex search.

Another way to limit file searches is by only choosing certain folder sets.

Instead of Ctrl + F, I think it is Ctrl + Shift + F which gives you the choice to specify file types, you wish to look into.