C# 数字输入框(自定义控件)

public partial class nTextBox : System.Windows.Forms.TextBox
    {
        #region 自定义成员
         private int maxIntegerLength = 10;
         private int minIntegerLength = 0;
         private int maxDecimalLength = 4;
         private int minDecimalLength = 0;
         private int integerLength;
         private int decimalLength;
         #endregion
 
         #region 自定义属性
         /// <summary>
         /// 最大整数位数
         /// </summary>
         public int MaxIntegerLength
         {
             get
             {
                 return maxIntegerLength;
             }
             set
             {
                 if (value >= 0 && value >= minIntegerLength)
                 {
                     maxIntegerLength = value;
                 }
                 else
                 {
                     throw new Exception("最大整数位数不应小于最小整数位数");
                 }
             }
         }
 
         /// <summary>
         /// 最小整数位数
         /// </summary>
         public int MinIntegerLength
         {
             get
             {
                 return minIntegerLength;
             }
             set
             {
                 if (value >= 0 && value <= maxIntegerLength)
                 {
                     minIntegerLength = value;
                 }
                 else
                 {
                     throw new Exception("最小整数位数不应大于最大整数位数");
                 }
             }
         }
 
         /// <summary>
         /// 最大小数位数
         /// </summary>
         public int MaxDecimalLength
         {
             get
             {
                 return maxDecimalLength;
             }
             set
             {
                 if (value >= 0 && value >= minDecimalLength)
                 {
                     maxDecimalLength = value;
                 }
                 else
                 {
                     throw new Exception("最大小数位数不应小于最小小数位数");
                 }
             }
         }
 
         /// <summary>
         /// 最小小数位数
         /// </summary>
         public int MinDecimalLength
         {
             get
            {
                return minDecimalLength;
            }
            set
            {
                if (value >= 0 && value <= maxDecimalLength)
                {
                    minDecimalLength = value;
                }
                else
                {
                    throw new Exception("最小小数位数不应大于最大小数位数");
                }
            }
        }
        #endregion

        #region 重写方法
        protected override void OnKeyPress(KeyPressEventArgs e)
        {
            int editIndex = SelectionStart;         //获取当前编辑位

            if (e.KeyChar == (char)Keys.Back) return;   //放行"退格"键

            if (e.KeyChar.Equals('.') || Char.IsNumber(e.KeyChar)) //过滤非数字与非小数点
            {
                if (Text.IndexOf(".") > -1)     //是否存在小数点
                {
                    //禁止重复输入小数点
                    if (e.KeyChar.Equals('.'))
                    {
                        e.Handled = true;
                        return;
                    }
                    else
                    {
                        if (SelectedText.Length > 0)
                        {
                            return;
                        }

                        integerLength = Text.IndexOf(".");
                        decimalLength = Text.Length - integerLength - 1;

                        //控制最大小数位数
                        if (decimalLength >= maxDecimalLength && editIndex > Text.IndexOf("."))
                        {
                            e.Handled = true;
                            return;
                        }

                        //控制最大整数位数
                        if (integerLength >= maxIntegerLength && editIndex <= Text.IndexOf("."))
                        {
                            e.Handled = true;
                            return;
                        }
                    }
                }
                else
                {  
                    //控制最大整数位数
                    integerLength = Text.Length;
                    if (integerLength == maxIntegerLength && !e.KeyChar.Equals('.'))
                    {
                        e.Handled = true;
                    }
                }
            }
            else
            {
                e.Handled = true;
            }

            base.OnKeyPress(e);
        }


        protected override void OnLeave(EventArgs e)
        {
            if (Text == null || Text == "") return;

            Text = Text.TrimStart('0');

            //取整数位数与小数位数
            if (Text.IndexOf(".") == -1)
            {
                integerLength = Text.Length;
                decimalLength = 0;
            }
            else
            {
                integerLength = Text.IndexOf(".");
                decimalLength = Text.Length - integerLength - 1;
                
                //验证小数位数是否符合最小值(不足补零)            
                if (decimalLength < minDecimalLength)
                {
                    Text = Text.PadRight(integerLength + minDecimalLength + 1, '0');
                }
            }

            //整数未输自动补零
            if (integerLength == 0)
            {
                Text = "0" + Text;
            }

            //验证整数位数是否符合最小值
            if (integerLength < minIntegerLength)
            {
                Focus();
                Select(0, integerLength);
            }

            //验证整数位数是否符合最大值
            if (integerLength > maxIntegerLength)
            {
                Focus();
                Select(0, integerLength);
            }
            base.OnLeave(e);
        }
        #endregion
    }