c#中WinForm的TextBox循环自动滚动示例

这个问题来自论坛提问，演示代码如下

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;
using System.Runtime.InteropServices;
namespace WindowsApplication27
... {
/**/ /// <summary>
/// 演示如何在TextBox中让文字循环滚动:
/// 作者jinjazz
/// 作者blog: http://blog.csdn.net/jinjazz
/// </summary>
public partial class Form1 : Form
... {
public Form1()
... {
InitializeComponent();

this .textBox1.Clear();
for ( int i = 0 ; i <= 20 ;i ++ )
... {
this .textBox1.Text += string .Format( " {0}:jinjazz__{1} " , i,i);
}
this .timer1.Interval = 200 ;
this .timer1.Start();
}

// 发送消息
[DllImport( " user32.dll " , EntryPoint = " SendMessage " )]
public static extern int SendMessage(IntPtr hWnd, int wMsg, int wParam, int lParam);
// 获取滚动条位置
[DllImport( " user32 " )]
public static extern int GetScrollPos(IntPtr hwnd, int nBar);
// 设置滚动条位置
[DllImport( " user32.dll " )]
static extern int SetScrollPos(IntPtr hWnd, int nBar,
int nPos, bool bRedraw);

public const int EM_LINESCROLL = 0xb6 ;

private void timer1_Tick( object sender, EventArgs e)
... {
int i = GetScrollPos( this .textBox1.Handle, 1 );

// 向下滚动一行
SendMessage( this .textBox1.Handle, EM_LINESCROLL, 0 , 1 ); // 0，1代表垂直滚动条向下滚动

// 判断是否有位置变化，如果没有则说明到了底部，返回开始处
if (i == GetScrollPos( this .textBox1.Handle, 1 ))
... {
// 回到顶部，这里用SetScrollPos似乎有问题，滚动条和文字不是同步更新
this .textBox1.SelectionStart = 0 ;
this .textBox1.SelectionLength = 1 ;
this .textBox1.ScrollToCaret();
this .textBox1.SelectionLength = 0 ;
}
Console.WriteLine(i);
}

private void textBox1_MouseEnter( object sender, EventArgs e)
... {
this .timer1.Stop();
}

private void textBox1_MouseLeave( object sender, EventArgs e)
... {
this .timer1.Start();
}
}
}