C#input输入框最后一位数字无法删除

t4.KeyPress += new System.Windows.Forms.KeyPressEventHandler(text_KeyPress);
t5.KeyPress += new System.Windows.Forms.KeyPressEventHandler(text_KeyPress);
t4.TextChanged += new EventHandler(text_TextChanged);
t5.TextChanged += new EventHandler(text_TextChanged);
在网上找到这两段代码，贴上去了，才发现输入数字后删除，个位总删不掉

C# code?123456789101112131415 private void text_KeyPress(object sender, KeyPressEventArgs e)         {             e.Handled = !(Char.IsNumber(e.KeyChar) || e.KeyChar == (char)8 || e.KeyChar == '.');             if (!e.Handled) (sender as TextBox).Tag = (sender as TextBox).Text;//记录最后一次正确输入            }           private void text_TextChanged(object sender, EventArgs e)         {             if (!System.Text.RegularExpressions.Regex.IsMatch((sender as TextBox).Text, @"^(?!0\d)\d+(\.\d*)?$"))             {                 int index = (sender as TextBox).SelectionStart;                 (sender as TextBox).Text = (sender as TextBox).Tag as string;                 (sender as TextBox).SelectionStart = index;             }         }
 
不知道是什么原因，是因为@"^(?!0\d)\d+(\.\d*)?$"吗
请教大神们 应该怎么修改啊？

因为空字符串不匹配@"^(?!0\d)\d+(\.\d*)?$")，这样文件就是用tag中的值（个位数）。
加个判断，如果为空字符串，不判断正则
        private void text_TextChanged(object sender, EventArgs e)         {             if ((sender as TextBox).Text == "")             {                 return;             }               if (!System.Text.RegularExpressions.Regex.IsMatch((sender as TextBox).Text, @"^(?!0\d)\d+(\.\d*)?$"))             {                 int index = (sender as TextBox).SelectionStart;                 (sender as TextBox).Text = (sender as TextBox).Tag as string;                 (sender as TextBox).SelectionStart = index;             }         }