如何獲得用戶定義的控件類

Question

我想要檢索的用戶自定義面板的OnPaint方法更新矩形電流控制手柄，但需要這種面板的手柄。我徘徊如何獲得當前控制的處理。該代碼是如下：

class MyPanel : Panel 
{ 
    [DllImport("User32.dll")] 
    public static extern bool GetUpdateRect(IntPtr hWnd, out Rectangle lpRect, bool bErase); 

    protected override void OnPaint(PaintEventArgs e) 
    { 
    Rectangle updateRect; 
    IntPtr hWnd = IntPtr.Zero; 
    // hWnd = ?; I wonder how to get handle of this panel 
    GetUpdateRect(hWnd, out updateRect, false); 

    base.OnPaint(e); 
    // following drawing code is omited 
    } 
} 

Answer 1

簡單的解決方案（因爲MyPanel已從Control具有HWND inherired）：

protected override void OnPaint(PaintEventArgs e) { 
    ... 
    // Panel is inherited from Control which has HWND 
    IntPtr hWnd = this.Handle; 
} 

複雜，但一般情況下溶液（MyPanel可以是任何類別，而不是必然 a Control）：

[DllImport("User32.dll")] 
private static extern IntPtr WindowFromDC(IntPtr hDC); 

// override: depending on MyClass it can be protected virtual void... 
protected override void OnPaint(PaintEventArgs e) { 
    ... 
    IntPtr hDC = e.Graphics.GetHdc(); 

    try { 
    IntPtr hWnd = WindowFromDC(hDC); 
    ... 
    } 
    finally { 
    e.Graphics.ReleaseHdc(hDC); 
    } 
}