required field validator in windows form

Validation is already built into the WinForms library.

Each Control-derived object has two events named Validating and Validated. Also it has a property called CausesValidation When this is set to true (it is true by default) then the control participates in validation. Otherwise, it does not.

  Validation occurs as part of focus.  When you focus off of a control,  its validation events are fired.  In fact the focus events are fired in  a specific order. 


   When you change the focus by using the   keyboard (TAB, SHIFT+TAB, and so on),   by calling the Select or   SelectNextControl methods, or by   setting the   ContainerControl..::.ActiveControl   property to the current form, focus   events occur in the following order:
      Enter
GotFocus
Leave
Validating
Validated
LostFocus 
      When you change the focus by using the   mouse or by calling the Focus method,   focus events occur in the following   order:
      Enter
GotFocus
LostFocus
Leave
Validating
Validated 
      If the CausesValidation property is   set to false, the Validating and   Validated events are suppressed.
      If the Cancel property of the   CancelEventArgs is set to true in the   Validating event delegate, all events   that would usually occur after the   Validating event are suppressed.
 

Check this.

http://msdn.microsoft.com/en-us/library/ms950965.aspx

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Santhosh Kumar Jayaraman14y ago
Validation is already built into the WinForms library.

Each Control-derived object has two events named Validating and Validated. Also it has a property called CausesValidation When this is set to true (it is true by default) then the control participates in validation. Otherwise, it does not.
Validation occurs as part of focus. When you focus off of a control, its validation events are fired. In fact the focus events are fired in a specific order. When you change the focus by using the keyboard (TAB, SHIFT+TAB, and so on), by calling the Select or SelectNextControl methods, or by setting the ContainerControl..::.ActiveControl property to the current form, focus events occur in the following order: Enter GotFocus Leave Validating Validated LostFocus When you change the focus by using the mouse or by calling the Focus method, focus events occur in the following order: Enter GotFocus LostFocus Leave Validating Validated If the CausesValidation property is set to false, the Validating and Validated events are suppressed. If the Cancel property of the CancelEventArgs is set to true in the Validating event delegate, all events that would usually occur after the Validating event are suppressed. Check this. http://msdn.microsoft.com/en-us/library/ms950965.aspx
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