原文出自 浆糊033，链接：https://www.cnblogs.com/maxin991025-/p/6219681.html

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 
}