Validating textboxes in C#

[xonel]

Hi

This code here below allows only numbers and one decimal point to be typed on a textbox.
It does not prevent you from:
1. Saving nulls in the database
2. From pasting any other character(words , asterisks,numbe rs etc) to the textbox.
What do i have to add to the code to prevent the two problems from occurring?? More so how to prevent nulls from being saved to the database
Here is my code:

private void txtBalance_TextChanged(object sender, EventArgs e) 
{ 
txtBalance.KeyPress += new KeyPressEventHandler(numbercheck_KeyPress); 
} 

private void numbercheck_KeyPress(object sender, KeyPressEventArgs e)
{
  if (!char.IsControl(e.KeyChar) && !char.IsDigit(e.KeyChar) && e.KeyChar != '.') 
{
e.Handled = true; 
}  
//only allow one decimal point 

if (e.KeyChar == '.' && (sender as TextBox).Text.IndexOf('.') > -1) 
{
e.Handled = true; 
} 
}

Please help me figure out
Thanks

[rpk2006]

For your first problem, disable "Allow Nulls" property in your database table (if using SQL Server).