调试易

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Drawing;
using System.Data;
using System.Text;
using System.Windows.Forms;namespace ViesSkyIPControl
{
    public partial class IPControl : UserControl
    {
        public IPControl()
        {
            InitializeComponent();
        }        public override string Text
        {
            set
            {
                string[] strIP = value.Split(new char[] {'.'});                if (strIP.Length == 4)
                {
                    if (IsIPValue(strIP[0]))
                    {
                        txtIP1.Text = strIP[0];
                    }
                    else
                    {
                        txtIP1.Text = "1";
                    }                    if (IsIPValue(strIP[1]))
                    {
                        txtIP2.Text = strIP[1];
                    }
                    else
                    {
                        txtIP2.Text = "0";
                    }                    if (IsIPValue(strIP[2]))
                    {
                        txtIP3.Text = strIP[2];
                    }
                    else
                    {
                        txtIP3.Text = "0";
                    }                    if (IsIPValue(strIP[3]))
                    {
                        txtIP4.Text = strIP[3];
                    }
                    else
                    {
                        txtIP4.Text = "0";
                    }
                }
                else
                {
                    txtIP1.Text = "1";
                    txtIP2.Text = "0";
                    txtIP3.Text = "0";
                    txtIP4.Text = "0";
                }
            }            get
            {
                return txtIP1.Text + "." + txtIP2.Text + "." + txtIP3.Text + "." + txtIP4.Text;
            }
        }        public bool Enable
        {
            set
            {
                if (value)
                {
                    txtIP1.Enabled = true;
                    txtIP2.Enabled = true;
                    txtIP3.Enabled = true;
                    txtIP4.Enabled = true;                    label1.Enabled = true;
                    label2.Enabled = true;
                    label3.Enabled = true;
                }
                else
                {
                    txtIP1.Enabled = false;
                    txtIP2.Enabled = false;
                    txtIP3.Enabled = false;
                    txtIP4.Enabled = false;                    label1.Enabled = false;
                    label2.Enabled = false;
                    label3.Enabled = false;
                }
            }            get
            {
                return txtIP1.Enabled;
            }
        }         private bool IsIPValue(string strValue)
        {
            int ipValue;            try
            {
                ipValue = Convert.ToInt32(strValue);
                if (ipValue >= 0 && ipValue <= 255)
                {
                    return true;
                }
            }
            catch (Exception e)
            {
                System.Console.WriteLine(e.Message);
            }            return false;
        }        private void EmulateIPControl(KeyPressEventArgs e, TextBox txtFore, TextBox txtCur, TextBox txtPost)
        {
            try
            {
                if (e.KeyChar.ToString() == "." || e.KeyChar.ToString() == "。" || e.KeyChar.ToString() == " ")
                {
                    if (txtCur.SelectedText.ToString() == "" && txtCur.Text.ToString() != "" && txtPost != null)
                    {
                        txtPost.Focus();
                        txtPost.SelectAll();
                    }
                    e.Handled = true;
                    return;
                }                if (e.KeyChar.ToString() == "\b")
                {
                    if (txtCur.Text.ToString() == "" && txtFore != null)
                    {
                        txtFore.Focus();   
                        txtFore.SelectAll();
                        e.Handled = true;                                        
                    }
                    
                    return;
                }
            }
            catch(Exception ex)
            {
                System.Console.WriteLine(ex.Message);
                e.Handled = true;
            }
        }        private void txtIP1_KeyPress(object sender, KeyPressEventArgs e)
        {
            EmulateIPControl(e, null, txtIP1, txtIP2);
        }        private void txtIP2_KeyPress(object sender, KeyPressEventArgs e)
        {
            EmulateIPControl(e, txtIP1, txtIP2, txtIP3);
        }        private void txtIP3_KeyPress(object sender, KeyPressEventArgs e)
        {
            EmulateIPControl(e, txtIP2, txtIP3, txtIP4);
        }        private void txtIP4_KeyPress(object sender, KeyPressEventArgs e)
        {
            EmulateIPControl(e, txtIP3, txtIP4, null);
        }        private bool IsEligibleData(string strData, int iFromBase)
        {
            char[] dataArray = strData.ToCharArray();
            int length = dataArray.Length;            switch(iFromBase)
            {
                case 10:     //10进制数
                    for (int i = 0; i < length; i++)
                    {
                        if (! (dataArray[i] <= '9' && dataArray[i] >= '0'))
                        {
                            return false;
                        }
                    }
                    break;                default:
                    break;
            }            return true;
        }        private void DealIPRule(TextBox txtCur)
        {
            while (txtCur.Text.Length > 3)
            {
                txtCur.Text = txtCur.Text.Remove(txtCur.Text.Length - 1, 1);
                txtCur.SelectionStart = txtCur.Text.Length;
            }
            txtCur.SelectionStart = txtCur.Text.Length;
            
            if (txtCur.Text.Length > 0)
            {
                while (! IsEligibleData(txtCur.Text, 10) && txtCur.Text.Length > 0)
                {
                    txtCur.Text = txtCur.Text.Remove(txtCur.Text.Length - 1, 1);
                    txtCur.SelectionStart = txtCur.Text.Length;
                }                if (txtCur.Text.Length > 0)
                {
                    int iIP = Convert.ToInt32(txtCur.Text);                    if (iIP > 255)
                    {
                        txtCur.Text = txtCur.Text.Remove(txtCur.Text.Length - 1, 1);
                        txtCur.SelectionStart = txtCur.Text.Length;                        return;
                    }
                }
            }                  
        }        

private void txtIP1_KeyUp(object sender, KeyEventArgs e)
        {            
            DealIPRule(txtIP1);            if (txtIP1.Text.Length > 0 && IsEligibleData(txtIP1.Text, 10))
            {
                int iIP = Convert.ToInt32(txtIP1.Text);
                string strErrorMsg = null;
                
                if (iIP == 127)
                {
                    strErrorMsg = "以 127 起头的 IP 地址无效，因为它们保留用作环回地址。";
                    strErrorMsg += "请在 1 和 223 之间指定一些其他有效值。";
                }                if (iIP > 223)
                {
                    strErrorMsg = iIP.ToString() + " 不是一个有效项目。请指定一个介于 1 和 223 之间的数值。";
                }                if (strErrorMsg != null)
                {
                    MessageBox.Show(strErrorMsg, "错误");
                    txtIP1.Text = "1";
                    if (iIP > 223)
                    {
                        txtIP1.Text = "223";
                    }
                    txtIP1.SelectionStart = txtIP1.Text.Length;
                    return;
                }                if (e.KeyCode.ToString() != "Back" && iIP > 99)
                {
                    txtIP2.Focus();
                }
            }
        }        private void txtIP2_KeyUp(object sender, KeyEventArgs e)
        {
            DealIPRule(txtIP2);            if (e.KeyCode.ToString() != "Back" && txtIP2.Text.Length > 2)
            {
                txtIP3.Focus();
            }
        }        private void txtIP3_KeyUp(object sender, KeyEventArgs e)
        {
            DealIPRule(txtIP3);            if (e.KeyCode.ToString() != "Back" && txtIP3.Text.Length > 2)
            {
                txtIP4.Focus();
            }
        }        private void txtIP4_KeyUp(object sender, KeyEventArgs e)
        {
            DealIPRule(txtIP4);
        }        private void TrimFrontZero(TextBox txtCur)
        {
            if (txtCur.Text.Length > 0 && IsEligibleData(txtCur.Text, 10))
            {
                int iIP = Convert.ToInt32(txtCur.Text);
                txtCur.Text = iIP.ToString();
            }
        }        private void txtIP1_LostFocus(object sender, EventArgs e)
        {
            TrimFrontZero(txtIP1);            if (txtIP1.Text.Length > 0 && IsEligibleData(txtIP1.Text, 10))
            {
                int iIP = Convert.ToInt32(txtIP1.Text);                                if (iIP == 0)
                {
                    string strErrorMsg = "0 不是一个有效项目。请指定一个介于 1 和 223 之间的数值。";
                    MessageBox.Show(strErrorMsg, "错误");
                    txtIP1.Text = "1";
                    txtIP1.SelectionStart = txtIP1.Text.Length;
                    txtIP1.Focus();
                }
            }
        }        private void txtIP2_LostFocus(object sender, EventArgs e)
        {
            TrimFrontZero(txtIP2);
        }        private void txtIP3_LostFocus(object sender, EventArgs e)
        {
            TrimFrontZero(txtIP3);
        }        private void txtIP4_LostFocus(object sender, EventArgs e)
        {
            TrimFrontZero(txtIP4);
        }
    }
}

新建windows forms control library工程
然后就可以自己定制了

给你一个例子
http://www.codeproject.com/KB/custom-controls/combobox.aspx
是一个可以进行输入的dropdownlist
这控件我经常用

你要做的是"自定义控件"，而不是"用户控件"给一个最简单的自定义控件新建一个类库工程，编写代码如下，请注意是否添加了System.Web.dll的引用：
using System;
using System.Web;
using System.Web.UI;namespace WishControls
{
    public class ControlDemo : Control
    {
        protected override void Render(HtmlTextWriter writer)
        {
            writer.Write ("<h1>Hello Wish</h1>");
        }
}然后在自定义控件项目的相同解决方案下添加一个网站项目，并在这个网站项目中添加对控件项目的引用（类库工程此时应已编译过）或者在工具箱上点击右键，在弹出的快捷菜单上单击”选择项”， 在打开的”选择工具箱项”窗口中选择”浏览”，选择刚才生成的dll文件，IDE会自动列出此dll中的所有控件，单击”确定”后，我们所创建的自定义控件就添加到工具箱中了（此时会自动添加对控件项目的引用）。

如果是VS2005，可以直接将继承自 WebControl 的 cs 文件拖放到工具栏
如果是VS2003， 需要手动在工具栏中添加整个DLL库

http://www.cnblogs.com/GoGoagg/category/56688.html

大家好像误会了我的意思，不是WEB控件，是窗体的控件，和WEB没关系。

窗体控件从UserControl继承,添加Form引用,然后输为*.dll
然后右击ToolBox控件箱选择"Choose Itmes",点击浏览,找到你的Dll,确定即可导入

我是继承的UserControl，也添加了Form引用，请问如何设置输出为DLL？
我只看到输出为windows应用程序，命令行应用程序和类库呀

右击工程,选择"properties",output type 选择为:class library