/// <summary>
/// 只显示下边框的TextBox控件
/// </summary>
public class BottomTextBox : TextBox
{
/// <summary>
/// 获得当前进程,以便重绘控件
/// </summary>
/// <param name="hWnd"></param>
/// <returns></returns>
[System.Runtime.InteropServices.DllImport("user32.dll")]
static extern IntPtr GetWindowDC(IntPtr hWnd);
/// <summary>
/// 释放控件
/// </summary>
/// <param name="hWnd"></param>
/// <param name="hDC"></param>
/// <returns></returns>
[System.Runtime.InteropServices.DllImport("user32.dll")]
static extern int ReleaseDC(IntPtr hWnd, IntPtr hDC);
/// <summary>
/// 重绘TextBox
/// </summary>
/// <param name="m"></param>
protected override void WndPro