C#通过窗口句柄获取textbox

可以通过以下代码通过窗口句柄获取指定窗口中的TextBox控件：

[DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]
private static extern IntPtr FindWindowEx(IntPtr parentHandle, IntPtr childAfter, string className, string windowTitle);

[DllImport("user32.dll", CharSet = CharSet.Auto)]
private static extern IntPtr SendMessage(IntPtr hWnd, uint msg, IntPtr wParam, StringBuilder lParam);

private const int WM_GETTEXT = 0x000D;

public static string GetTextBoxText(IntPtr parentHandle, string textBoxClassName, string textBoxTitle)
{
    IntPtr textBoxHandle = FindWindowEx(parentHandle, IntPtr.Zero, textBoxClassName, textBoxTitle);
    if (textBoxHandle == IntPtr.Zero)
    {
        return string.Empty;
    }

    StringBuilder sb = new StringBuilder(256);
    SendMessage(textBoxHandle, WM_GETTEXT, (IntPtr)sb.Capacity, sb);
    return sb.ToString();
}

调用示例：

IntPtr parentHandle = // 父窗口句柄
string textBoxClassName = "TextBox"; // TextBox控件的类名
string textBoxTitle = "TextBox1"; // TextBox控件的标题

string text = GetTextBoxText(parentHandle, textBoxClassName, textBoxTitle);