制作一个可以输入 IP 地址的控件

准备工作：
1. 首先，打开vs.net，新建一个C#类库项目。如叫 IpBoxControl。
2. 在vs.net 的菜单，“项目”，“添加用户控件”，把这个用户控件取名为IpBox。
3. 把一个Panel从工具箱拖到IpBox的设计视图，取名为panel1，设置panel1的Location为(0,0)，Size为(136, 20)，BorderStyle为Fixed3D，BackColor为Window。
4. 把一个TextBox从工具箱拖到panel1里。取名为textBox1，设置textBox1的Location为(8,0)，Size为(20, 14)，BorderStyle为None，MaxLength为3，TextAlign为Center，Text为““，BackColor为Window。
5. 把一个Label从工具箱拖到panel1里。取名为label1，设置label1的Location为(32, 0)，Size为(8, 14)，BorderStyle为None，TextAlign为TopCenter，Text为“.”，BackColor为Window。
6. 选取textBox1和label1，textBox1复制、粘贴上3份，label1复制、粘贴上2份。分别命名为textBox2、label2，textBox3、label3，textBox4。Location分别为(40, 0)、(64, 0)、(72, 0)、(96, 0)、(104, 0)。
7. 设置IpBox的Location为(0,0)，Size为(136, 20)。

现在一个ip box 的形状已经出来了，接下来要在程序里实现输入的控制。
源代码如下：

using System;
using System.Collections;
using System.ComponentModel;
using System.Drawing;
using System.Data;
using System.Windows.Forms;
using System.Text.RegularExpressions;

namespace XRascal.Controls
{
/// <summary>
/// UserControl1 的摘要说明。
/// </summary>
[
Description("横刀夺爱的 Ip Box 控件！用于输入 IP 地址。"),
ToolboxBitmap(typeof(XRascal.Controls.IpBox))
]
public class IpBox : System.Windows.Forms.UserControl
{
private System.Windows.Forms.Panel panel1;
private System.Windows.Forms.TextBox textBox4;
private System.Windows.Forms.Label label3;
private System.Windows.Forms.TextBox textBox3;
private System.Windows.Forms.Label label2;
private System.Windows.Forms.TextBox textBox2;
private System.Windows.Forms.Label label1;
private System.Windows.Forms.TextBox textBox1;
private string _text = "";
/// <summary>
/// 必需的设计器变量。
/// </summary>
private System.ComponentModel.Container components = null;

public IpBox()
{
// 该调用是 Windows.Forms 窗体设计器所必需的。
InitializeComponent();

// TODO: 在 InitializeComponent 调用后添加任何初始化

}

/// <summary>
/// 清理所有正在使用的资源。
/// </summary>
protected override void Dispose( bool disposing )
{
if( disposing )
{
if(components != null)
{
components.Dispose();
}
}
base.Dispose( disposing );
}

#region 组件设计器生成的代码
/// <summary>
/// 设计器支持所需的方法 - 不要使用代码编辑器
/// 修改此方法的内容。
/// </summary>
private void InitializeComponent()
{
this.panel1 = new System.Windows.Forms.Panel();
this.textBox4 = new System.Windows.Forms.TextBox();
this.label3 = new System.Windows.Forms.Label();
this.textBox3 = new System.Windows.Forms.TextBox();
this.label2 = new System.Windows.Forms.Label();
this.textBox2 = new System.Windows.Forms.TextBox();
this.label1 = new System.Windows.Forms.Label();
this.textBox1 = new System.Windows.Forms.TextBox();
this.panel1.SuspendLayout();
this.SuspendLayout();
//
// panel1
//
this.panel1.BackColor = System.Drawing.Color.White;
this.panel1.BorderStyle = System.Windows.Forms.BorderStyle.Fixed3D;
this.panel1.Controls.Add(this.textBox4);
this.panel1.Controls.Add(this.label3);
this.panel1.Controls.Add(this.textBox3);
this.panel1.Controls.Add(this.label2);
this.panel1.Controls.Add(this.textBox2);
this.panel1.Controls.Add(this.label1);
this.panel1.Controls.Add(this.textBox1);
this.panel1.Location = new System.Drawing.Point(0, 0);
this.panel1.Name = "panel1";
this.panel1.Size = new System.Drawing.Size(136, 20);
this.panel1.TabIndex = 1;
//
// textBox4
//
this.textBox4.BorderStyle = System.Windows.Forms.BorderStyle.None;
this.textBox4.Location = new System.Drawing.Point(104, 0);
this.textBox4.MaxLength = 3;
this.textBox4.Name = "textBox4";
this.textBox4.Size = new System.Drawing.Size(20, 14);
this.textBox4.TabIndex = 6;
this.textBox4.TextAlign = System.Windows.Forms.HorizontalAlignment.Center;
this.textBox4.KeyPress += new System.Windows.Forms.KeyPressEventHandler(this.textBox4_KeyPress);
//
// label3
//
this.label3.Location = new System.Drawing.Point(96, 0);
this.label3.Name = "label3";
this.label3.Size = new System.Drawing.Size(8, 14);
this.label3.TabIndex = 5;
this.label3.Text = ".";
this.label3.TextAlign = System.Drawing.ContentAlignment.TopCenter;
//
// textBox3
//
this.textBox3.BorderStyle = System.Windows.Forms.BorderStyle.None;
this.textBox3.Location = new System.Drawing.Point(72, 0);
this.textBox3.MaxLength = 3;
this.textBox3.Name = "textBox3";
this.textBox3.Size = new System.Drawing.Size(20, 14);
this.textBox3.TabIndex = 4;
this.textBox3.TextAlign = System.Windows.Forms.HorizontalAlignment.Center;
this.textBox3.KeyPress += new System.Windows.Forms.KeyPressEventHandler(this.textBox3_KeyPress);
//
// label2
//
this.label2.Location = new System.Drawing.Point(64, 0);
this.label2.Name = "label2";
this.label2.Size = new System.Drawing.Size(8, 14);
this.label2.TabIndex = 3;
this.label2.Text = ".";
this.label2.TextAlign = System.Drawing.ContentAlignment.TopCenter;
//
// textBox2
//
this.textBox2.BorderStyle = System.Windows.Forms.BorderStyle.None;
this.textBox2.Location = new System.Drawing.Point(40, 0);
this.textBox2.MaxLength = 3;
this.textBox2.Name = "textBox2";
this.textBox2.Size = new System.Drawing.Size(20, 14);
this.textBox2.TabIndex = 2;
this.textBox2.TextAlign = System.Windows.Forms.HorizontalAlignment.Center;
this.textBox2.KeyPress += new System.Windows.Forms.KeyPressEventHandler(this.textBox2_KeyPress);
//
// label1
//
this.label1.Location = new System.Drawing.Point(32, 0);
this.label1.Name = "label1";
this.label1.Size = new System.Drawing.Size(8, 14);
this.label1.TabIndex = 1;
this.label1.Text = ".";
this.label1.TextAlign = System.Drawing.ContentAlignment.TopCenter;
//
// textBox1
//
this.textBox1.BorderStyle = System.Windows.Forms.BorderStyle.None;
this.textBox1.Location = new System.Drawing.Point(8, 0);
this.textBox1.MaxLength = 3;
this.textBox1.Name = "textBox1";
this.textBox1.Size = new System.Drawing.Size(20, 14);
this.textBox1.TabIndex = 0;
this.textBox1.TextAlign = System.Windows.Forms.HorizontalAlignment.Center;
this.textBox1.KeyPress += new System.Windows.Forms.KeyPressEventHandler(this.textBox1_KeyPress);
//
// IpBox
//
this.Controls.Add(this.panel1);
this.Name = "IpBox";
this.Size = new System.Drawing.Size(136, 20);
this.panel1.ResumeLayout(false);
this.ResumeLayout(false);

}
#endregion

private void textBox1_KeyDown(object sender, System.Windows.Forms.KeyEventArgs e)
{
//System.Text.Encoding.GetEncoding(0).GetString();
}

private void textBox1_KeyPress(object sender, System.Windows.Forms.KeyPressEventArgs e)
{
MaskIpAddr( textBox1, e );
}

private void textBox2_KeyPress(object sender, System.Windows.Forms.KeyPressEventArgs e)
{
MaskIpAddr( textBox2, e );
}

private void textBox3_KeyPress(object sender, System.Windows.Forms.KeyPressEventArgs e)
{
MaskIpAddr( textBox3, e );
}

private void textBox4_KeyPress(object sender, System.Windows.Forms.KeyPressEventArgs e)
{
MaskIpAddr( textBox4, e );
}

private void MaskIpAddr( System.Windows.Forms.TextBox textBox, KeyPressEventArgs e)
{
int len = textBox.Text.Length;

if(Char.IsDigit(e.KeyChar) || e.KeyChar == '.' || e.KeyChar == 8)
{
if (e.KeyChar != 8)
{
if(len == 2 && e.KeyChar != '.')
{
string tmp = textBox.Text + e.KeyChar;
if( textBox.Name == "textBox1" )
{
if(Int32.Parse(tmp)> 223) // 进行验证
{
MessageBox.Show( tmp + " 不是一个有效项目。请指定一个介于 1 和 223 之间的数值。");
textBox.Text = "223";
textBox.Focus();
return;
}

textBox2.Focus();
textBox2.SelectAll();

}
else if( textBox.Name == "textBox2" )
{
if(Int32.Parse(tmp)> 255)
{
MessageBox.Show( tmp + " 不是一个有效项目。请指定一个介于 1 和 255 之间的数值。");
textBox.Text = "255";
textBox.Focus();
return;
}
textBox3.Focus();
textBox3.SelectAll();
}
else if( textBox.Name == "textBox3" )
{
if(Int32.Parse(tmp)> 255)
{
MessageBox.Show( tmp + " 不是一个有效项目。请指定一个介于 1 和 255 之间的数值。");
textBox.Text = "255";
textBox.Focus();
return;
}
textBox4.Focus();
textBox4.SelectAll();
}
else if( textBox.Name == "textBox4" )
{
if(Int32.Parse(tmp)> 255)
{
MessageBox.Show( tmp + " 不是一个有效项目。请指定一个介于 1 和 255 之间的数值。");
textBox.Text = "255";
textBox.Focus();
return;
}

}

}
if(e.KeyChar == '.')
{
if( textBox.Name == "textBox1" && textBox.Text != "" )
{
textBox2.Focus();
textBox2.SelectAll();
}
if( textBox.Name == "textBox2" && textBox.Text != "" )
{
textBox3.Focus();
textBox3.SelectAll();
}
if( textBox.Name == "textBox3" && textBox.Text != "" )
{
textBox4.Focus();
textBox4.SelectAll();
}
if( textBox.Name == "textBox4" && textBox.Text != "" )
{

}
e.Handled = true;
}
}
else
{
if( textBox.Name == "textBox1" && textBox.Text == "")
{

}
if( textBox.Name == "textBox2" && textBox.Text == "")
{
textBox1.Focus();
textBox1.SelectionStart = textBox1.Text.Length;
}
if( textBox.Name == "textBox3" && textBox.Text == "")
{
textBox2.Focus();
textBox2.SelectionStart = textBox2.Text.Length;
}
if( textBox.Name == "textBox4" && textBox.Text == "")
{
textBox3.Focus();
textBox3.SelectionStart = textBox3.Text.Length;
}
e.Handled = false;
}
}
else
e.Handled = true;
}

[Browsable(true)]
/// <summary>
/// 获取 IpBox 的文本。
/// </summary>
public new string Text
{
get
{
if( textBox1.Text == ""
|| textBox2.Text == ""
|| textBox3.Text == ""
|| textBox4.Text == "")
{
_text = "";
return _text;
}
else
{
_text = Convert.ToInt32(textBox1.Text).ToString() + "." + Convert.ToInt32(textBox2.Text).ToString() + "." + Convert.ToInt32(textBox3.Text).ToString() + "." + Convert.ToInt32(textBox4.Text).ToString();
return _text;
}

}
/* set //
{
if(value != null)
{
// 255-255-255-255
//string pattern = @"^([1-9]|/d{2}|1[0-9]{1,2}|2[0-5]{2})/.(/d{1,2}|1[0-9]{1,2}|[1-2][0-5]{2})/.(/d{1,2}|1[0-9]{1,2}|[1-2][0-5]{2})/.(/d{1,2}|1[0-9]{1,2}|[1-2][0-5]{2})$";
// 223-255-255-255
string pattern = @"^([1-9]|/d{2}|1[0-9]{1,2}|2[1-2][1-3])/.(/d{1,2}|1[0-9]{1,2}|[1-2][0-5]{2})/.(/d{1,2}|1[0-9]{1,2}|[1-2][0-5]{2})/.(/d{1,2}|1[0-9]{1,2}|[1-2][0-5]{2})$";

if( !Regex.IsMatch(value , pattern) )
{
_text = "";
throw new Exception("IP 地址格式错误！");
}
else
{
string[] ipnum = value.Split('.');
textBox1.Text = ipnum[0];
textBox2.Text = ipnum[1];
textBox3.Text = ipnum[2];
textBox4.Text = ipnum[3];
}
}

_text = value;

}
*/

}

}
}

最后，我们要来测试这个控件：

在项目的解决方案里，右击解决方案的属性，新建一个C# 的Windows应用程序项目，取名为TestIpBox。
双击打开 Form1.cs的设计视图，右击工具箱，“添加/移除项”，“浏览”找到刚做好的 dll ，选择，确定。把这个控件从工具箱里拖到Form1的设计视图里。
把 TestIpBox 设成启动项目，按 F5 测试。