>Thanks.
>
>Sometimes i have found with this.
>
>if i make a control in a class library and i add this project reference to my application and place the control in a form, if i build again the class library, the control desappear.
>
>What should i do to avoid this.

Wilson;

If I understand the question correctly, if you are using Visual Studio .NET, have you added the new control to Tools/Customize Tool Box?

Tom