using System;using System.Collections.Generic;using System.ComponentModel;using System.Drawing;using System.Data;using System.Text;using System.Windows.Forms;using System.Text.RegularExpressions;namespace IPInputControl.Ctrl{ public partial class IPInput : UserControl { public IPInput() {  InitializeComponent(); } TextBox ParentTxt; private void IPInput_Load(object sender, EventArgs e) {  ParentTxt = txt_1; } public void txt_KeyDown(object sender, KeyEventArgs e) {  ParentTxt = (TextBox)sender;  if (e.KeyCode == Keys.Left)  {  switch (ParentTxt.Name.Split('_')[1])  {   case "1":   break;   case "2":   if (ParentTxt.SelectionStart == 0 && ParentTxt.Text != "")   {    if (int.Parse(ParentTxt.Text) > 255)    {    MessageBox.Show(ParentTxt.Text + "不是有效項。請指定一個介于1和255之間的值。", "錯誤", MessageBoxButtons.OK, MessageBoxIcon.Warning);    ParentTxt.Text = "255";    ParentTxt.SelectionStart = 0;    }    else    {    txt_1.Focus();    }   }   else if (ParentTxt.Text == "")   {    txt_1.Focus();   }   break;   case "3":   if (ParentTxt.SelectionStart == 0 && ParentTxt.Text != "")   {    if (int.Parse(ParentTxt.Text) > 255)    {    MessageBox.Show(ParentTxt.Text + "不是有效項。請指定一個介于1和255之間的值。", "錯誤", MessageBoxButtons.OK, MessageBoxIcon.Warning);    ParentTxt.Text = "255";    ParentTxt.SelectionStart = 0;    }    else    {    txt_2.Focus();    }   }   else if (ParentTxt.Text == "")   {    txt_2.Focus();   }   break;   case "4":   if (ParentTxt.SelectionStart == 0 && ParentTxt.Text != "")   {    if (int.Parse(ParentTxt.Text) > 255)    {    MessageBox.Show(ParentTxt.Text + "不是有效項。請指定一個介于1和255之間的值。", "錯誤", MessageBoxButtons.OK, MessageBoxIcon.Warning);    ParentTxt.Text = "255";    ParentTxt.SelectionStart = 0;    }    else    {    txt_3.Focus();    }   }   else if (ParentTxt.Text == "")   {    txt_3.Focus();   }   break;  }  }  else if (e.KeyCode == Keys.Right)  {  switch (ParentTxt.Name.Split('_')[1])  {   case "1":   if (ParentTxt.SelectionStart == ParentTxt.Text.Length && ParentTxt.Text != "")   {    if (int.Parse(ParentTxt.Text) > 223)    {    MessageBox.Show(ParentTxt.Text + "不是有效項。請指定一個介于1和223之間的值。", "錯誤", MessageBoxButtons.OK, MessageBoxIcon.Warning);    ParentTxt.Text = "223";    ParentTxt.SelectionStart = ParentTxt.Text.Length;    }    else    {    txt_2.Focus();    }   }   else if (ParentTxt.Text == "")   {    txt_2.Focus();   }   break;   case "2":   if (ParentTxt.SelectionStart == ParentTxt.Text.Length && ParentTxt.Text != "")   {    if (int.Parse(ParentTxt.Text) > 255)    {    MessageBox.Show(ParentTxt.Text + "不是有效項。請指定一個介于1和255之間的值。", "錯誤", MessageBoxButtons.OK, MessageBoxIcon.Warning);    ParentTxt.Text = "255";    ParentTxt.SelectionStart = ParentTxt.Text.Length;    }    else    {    txt_3.Focus();    }   }   else if (ParentTxt.Text == "")   {    txt_3.Focus();   }   break;   case "3":   if (ParentTxt.SelectionStart == ParentTxt.Text.Length && ParentTxt.Text != "")   {    if (int.Parse(ParentTxt.Text) > 255)    {    MessageBox.Show(ParentTxt.Text + "不是有效項。請指定一個介于1和255之間的值。", "錯誤", MessageBoxButtons.OK, MessageBoxIcon.Warning);    ParentTxt.Text = "255";    ParentTxt.SelectionStart = ParentTxt.Text.Length;    }    else    {    txt_4.Focus();    }   }   else if (ParentTxt.Text == "")   {    txt_4.Focus();   }   break;   case "4":   break;  }  } } public void txt_KeyPress(object sender, KeyPressEventArgs e) {  ParentTxt = (TextBox)sender;  Regex regex = new Regex(@"^[0-9]+$");  if (!regex.IsMatch(e.KeyChar.ToString()) && e.KeyChar != (Char)Keys.Back)  {  e.Handled = true;  }  else if (e.KeyChar == (Char)Keys.Back)  {  e.Handled = false;  switch (ParentTxt.Name.Split('_')[1])  {   case "1":   break;   case "2":   if (ParentTxt.SelectionStart == 0)   {    txt_1.Focus();    if (txt_1.Text != "")    {    txt_1.Text = txt_1.Text.Substring(0, txt_1.Text.Length - 1);    }    txt_1.SelectionStart = txt_1.Text.Length;   }   break;   case "3":   if (ParentTxt.SelectionStart == 0)   {    txt_2.Focus();    if (txt_2.Text != "")    {    txt_2.Text = txt_2.Text.Substring(0, txt_2.Text.Length - 1);    }    txt_2.SelectionStart = txt_2.Text.Length;   }   break;   case "4":   if (ParentTxt.SelectionStart == 0)   {    txt_3.Focus();    if (txt_3.Text != "")    {    txt_3.Text = txt_3.Text.Substring(0, txt_3.Text.Length - 1);    }    txt_3.SelectionStart = txt_3.Text.Length;   }   break;  }  }  else  {  switch (ParentTxt.Name.Split('_')[1])  {   case "1":   if (ParentTxt.SelectionStart == ParentTxt.Text.Length)   {    if (int.Parse(ParentTxt.Text + e.KeyChar.ToString()) > 223)    {    MessageBox.Show(ParentTxt.Text + e.KeyChar.ToString() + "不是有效項。請指定一個介于1和223之間的值。", "錯誤", MessageBoxButtons.OK, MessageBoxIcon.Warning);    e.Handled = true;    ParentTxt.Text = "223";    }    else    {    e.Handled = false;    }   }   else if(ParentTxt.Text.Length != 3)   {    e.Handled = false;   }   else   {    e.Handled = true;   }   break;   default:   if (ParentTxt.SelectionStart == ParentTxt.Text.Length)   {    if (int.Parse(ParentTxt.Text + e.KeyChar.ToString()) > 255)    {    MessageBox.Show(ParentTxt.Text + e.KeyChar.ToString() + "不是有效項。請指定一個介于1和255之間的值。", "錯誤", MessageBoxButtons.OK, MessageBoxIcon.Warning);    e.Handled = true;    ParentTxt.Text = "255";    }    else    {    e.Handled = false;    }   }   else if (ParentTxt.Text.Length != 3)   {    e.Handled = false;   }   else   {    e.Handled = true;   }   break;  }  } } public void txt_TextChanged(object sender, EventArgs e) {  if (ParentTxt.Text.Length == 3)  {  switch (ParentTxt.Name.Split('_')[1])  {   case "1":   if (ParentTxt.SelectionStart == ParentTxt.Text.Length)   {    txt_2.Focus();   }   break;   case "2":   if (ParentTxt.SelectionStart == ParentTxt.Text.Length)   {    txt_3.Focus();   }   break;   case "3":   if (ParentTxt.SelectionStart == ParentTxt.Text.Length)   {    txt_4.Focus();   }   break;   case "4":   break;  }  } } }}

using System;using System.Collections.Generic;using System.ComponentModel;using System.Drawing;using System.Data;using System.Text;using System.Windows.Forms;using System.Text.RegularExpressions;namespace IPInputControl.Ctrl{ public partial class ControlText : TextBox { public ControlText() {  InitializeComponent(); } public void txt_TextChange(object sender, EventArgs e) {  if (this.Text.Length == 3)  {  SendKeys.Send("{TAB}");  } } protected override bool ProcessCmdKey(ref Message msg, Keys keyData) {  if (keyData == Keys.Tab)  {  return true;  }  return base.ProcessCmdKey(ref msg, keyData); } }}