Question

I have a TextBox which should only accept numbers (they can be simple int or float with E as power factor).

So some valid examples are:

1
+1.1
0
.1
1E-1
1e-2
-1.66
-6e-10

non-valid example:

  E-1

Generally it should start with either a number or + and – signs or a DOT.

Then I will put this in TextChanged event and it will be fine.

 textBox.Text = Regex.Replace(textBox.Text, @"[\d]", ""); //so useless!

Answer 1

If you want your exponents to be used, try this (be sure to add using System.Globalization;):

decimal value;
if(Decimal.TryParse(textBox.Text, NumberStyles.Float, CultureInfo.CurrentCulture, out value))
{
    textBox.Text = value.ToString();
}