How to Manually Raise a Paint Event in Windows Forms: Invalidate(), Update(), or Refresh()?

Manually trigger draw events

In scenarios where manual refresh of the display is required, draw events can be called through specific methods in the form or control.

Invalidate()

Calling this method will request a delayed redraw through the standard message loop system. It provides a more efficient approach by combining multiple invalidation operations into a single redraw operation.

Update()

This method forces redrawing of invalid areas. This is useful when an immediate redraw is required. However, it may cause continuous redraws due to interaction with other controls that may invalidate the area.

Refresh()

This method combines the functionality of Invalidate() and Update(). It invalidates the region and forces an immediate redraw. While convenient, it can cause excessive redraws if other controls also become invalid.

Best Practices

Typically, it is recommended to use Invalidate() in most situations because it conforms to Windows' efficient screen update mechanism. Update() should be used with caution, especially when handling consecutive changes within a loop. If you must redraw immediately, you can use Refresh(), but this requires careful consideration of the potential performance impact.

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