Problems rebuilding

I am new to this post. And i'm new also in c#.... I hope someone can help me. I'm creating a solution in visual studio 2005. Inside the solution, i create a website, which uses a control that i have create, to manage ink. When i create the solution, i have no problem. The control works perfectly. I can paint, and recognize the strokes drawn. But each time i modify the control code, when i rebuild the solution, the control doesn't work. I must create a new solution, with the new code, since the begining. Has anybody found this behaviour? I'm totally lost, and i don't know what to do... Thank you very much!!