//判断按键是不是要输入的类型。if (((int)e.KeyChar < 48 || (int)e.KeyChar > 57) && (int)e.KeyChar != 8 && (int)e.KeyChar != 46)e.Handled = true;//小数点的处理。if ((int)e.KeyChar == 46)                           //小数点{if (textBox1.Text.Length <= 0)e.Handled = true;   //小数点不能在第一位else{float f;float oldf;bool b1 = false, b2 = false;b1 = float.TryParse(textBox1.Text, out oldf);b2 = float.TryParse(textBox1.Text + e.KeyChar.ToString(), out f);if (b2 == false){if (b1 == true)e.Handled = true;elsee.Handled = false;}}}

方法一：  private void tBox_KeyPress(object sender, KeyPressEventArgs e)  {  if (e.KeyChar == 0x20) e.KeyChar = (char)0;  //禁止空格键  if ((e.KeyChar == 0x2D) && (((TextBox)sender).Text.Length == 0)) return;   //处理负数  if (e.KeyChar > 0x20)  {  try  {  double.Parse(((TextBox)sender).Text + e.KeyChar.ToString());  }  catch  {  e.KeyChar = (char)0;   //处理非法字符  }  }
}  方法二：  private void TextBox_KeyPress(object sender, KeyPressEventArgs e)  {  if(e.KeyChar!=8&&!Char.IsDigit(e.KeyChar))  {  e.Handled = true;  }
}
或者  private void TextBox_KeyPress(object sender, KeyPressEventArgs e)
{  if(e.KeyChar!='\b'&&!Char.IsDigit(e.KeyChar))  {  e.Handled = true;  }  }  方法三:  private void textBox1_KeyPress(object sender, System.Windows.Forms.KeyPressEventArgs e)
{
if(e.KeyChar!='\b')//这是允许输入退格键
{
if((e.KeyChar<'0')||(e.KeyChar>'9'))//这是允许输入0-9数字
{
e.Handled = true;
}
}
}  方法四:  private void textBox1_Validating(object sender, CancelEventArgs e)
{
const string pattern = @"^\d+\.?\d+{1}quot;;
string content = ((TextBox)sender).Text;   if (!(Regex.IsMatch(content, pattern)))
{
errorProvider1.SetError((Control)sender, "只能输入数字!");
e.Cancel = true;
}
else
errorProvider1.SetError((Control)sender, null);
}  方法五:  private void textBox1_KeyPress(object sender, System.Windows.Forms.KeyPressEventArgs e)
{
if(e.KeyChar=='.' && this.textBox1.Text.IndexOf(".")!=-1)
{
e.Handled=true;
}  if(!((e.KeyChar>=48 && e.KeyChar<=57) || e.KeyChar=='.' || e.KeyChar==8))
{
e.Handled=true;
}  }  方法六：  private void tbx_LsRegCapital_KeyPress(object sender, KeyPressEventArgs e)
{  if (!Char.IsNumber(e.KeyChar) && !Char.IsPunctuation(e.KeyChar) && !Char.IsControl(e.KeyChar))  {  e.Handled = true;//消除不合适字符  }  else if (Char.IsPunctuation(e.KeyChar))  {  if (e.KeyChar != '.' || this.textBox1.Text.Length == 0)//小数点  {  e.Handled = true;  }  if (textBox1.Text.LastIndexOf('.') != -1)  {  e.Handled = true;  }  }        }    方法七:  利用ASCII码处理办法、
{  if ((e.KeyChar <= 48 || e.KeyChar >=57) && (e.KeyChar != 8) && (e.KeyChar != 46))  e.Handled = true;
================48代表0，57代表9，8代表空格，46代表小数点
}