Why Aren't My Arrow Keys Triggering KeyDown Events in My Windows Application?

Solution to the problem that arrow keys cannot trigger the KeyDown event in Windows applications

When building an application that relies solely on the Windows operating system for key input handling, you may encounter a strange problem: the arrow keys fail to trigger the KeyDown event under certain circumstances.

This problem only occurs when the arrow keys are pressed alone, but the event can be triggered normally when pressed in combination with the control keys. To solve this problem, the key is to understand the role of the PreviewKeyDown event, which allows access to key events before they reach a specific control.

According to Microsoft's official documentation, the solution is to set e.IsInputKey = true in the PreviewKeyDown event after detecting the arrow keys. By doing this, the KeyDown event will be fired correctly.

This approach provides a more elaborate solution than overriding the ProcessCMDKey method (used for menu item key event overrides). The desired key event handling can be restored by leveraging the PreviewKeyDown event and setting e.IsInputKey to true.

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