I can think of two things:
1. If it is an ordinary button, the CausesValidation property of the Button might be false. This is not the default, but verify.
2. if it is a toolbar button, these do not validate and there is no CausesValidation property. You can force validation in the ToolClick handler by calling the Form's Validate method.
| privatevoidtoolStripButton1_Click(objectsender,EventArgse) |
| { |
| if(this.Validate()) |
| { |
| //Validationokay.Proceed. |
| } |
| } |