How Can I Programmatically Generate Keypress Events in C#?

Procedural generation of C# key events

In application development, it is often necessary to programmatically generate key events to simulate user input or test event handling mechanisms. This article will guide you on how to create such events in C# using various methods, including specific methods for WPF, WinForms, and Win32.

WPF specific methods

For WPF applications, you can simulate key events using the KeyEventArgs class construct and then use the RaiseEvent method to raise it on the target element. For example, to send the KeyDown event of the Insert key to the currently focused element:

<code class="language-csharp">var key = Key.Insert;                    // 要发送的键
var target = Keyboard.FocusedElement;    // 目标元素
var routedEvent = Keyboard.KeyDownEvent; // 要发送的事件
target.RaiseEvent(
  new KeyEventArgs(
    Keyboard.PrimaryDevice,
    PresentationSource.FromVisual(target),
    0,
    key)
  { RoutedEvent=routedEvent }
);</code>

WinForms specific methods

In WinForms, you can simulate key events using the SendKeys.Send method. For example, to send the Insert keystroke:

<code class="language-csharp">SendKeys.Send("{INSERT}");</code>

Win32 specific methods

For low-level control over keystroke simulation, you can use the keybd_event functions from the Windows API. This function allows you to specify virtual key codes, scan codes, and other parameters that simulate key events. For example, to send the keydown event of the Insert key:

<code class="language-csharp">// 导入必要的头文件。
[DllImport("user32.dll")]
private static extern void keybd_event(byte bVk, byte bScan, uint dwFlags, int dwExtraInfo);

// ...

// 定义keydown事件的参数。
const byte VK_INSERT = 0x2D; // Insert键的虚拟键代码。
keybd_event(VK_INSERT, 0, 0, 0); // 发送keydown事件。</code>

Other instructions

• Controls typically expect to receive preview events before regular events. When simulating key events, make sure to follow this order.
• target.RaiseEvent(...)Sends events directly to the target element without any meta-processing. This is usually ideal. However, if you want to simulate actual keyboard keys, use InputManager.ProcessInput() instead.
• The method of simulating text input events is different from the method of simulating key events.

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