Partial Classes and Form Designers
I knew that partial classes were going to make development easier by allowing us to segment code logically into files, but I never expected that partial classes would be used as well as they are, by the environment, directly.
When I first started playing with a Winforms project, I added a couple of controls to my form and then dropped into the code for that form. What did I find? A whole lot nothing...
My form:
My code class:
Being completely confused by this, i hopped over to the Solution Explorer and clicked on the "Show All Files Option", so that I could take a look at the .resx file and see if everything was being put in place properly. When I did this, i was pleasantly supprised by the existance of a ".designer.vb" class.
Obviously, someone at Microsoft listened to all the comaplaints about how horrible it was to have our Winforms code files cluttered up with those horrible "Winforms Designer" regions. And here, we have a perfect example of how Partial classes can simplify a project, simply through organization of code into seperate files. I no longer have to wade through hundreds of lines of winforms designer code when i want to add a new event handler or other method to my Winforms classes. All of the guts and layout code for my Winforms controls are now stored in the .designer.vb Partial class. Here's a portion of the class that was created for me:
The only "issue" here, is that I have to remember that my class was Inherited in the partial class, and not in my code class. If I try to specify inheritance in my code class, i end up with this error:
Base class 'System.MarshalByRefObject' specified for class 'Form1' cannot be different from the base class 'System.Windows.Forms.Form' of one of its other partial types. D:\Documents and Settings\dbailey\My Documents\Visual Studio 2005\Projects\WindowsApplication1\WindowsApplication1\Form1.vb 2 11 WindowsApplication1
No big deal, though. This is just a friendly reminder that I've already inherited this class from another type, somewhere else. It would be nice if the error message specially told me which file the inheritance was done in, though.