How can I make it so that only numbers can be entered in the TextBox and the first one is not 0?

I need to make it so that only numbers can be entered in the TextBox and so that the first one is not 0. I have a code so that you can enter only numbers, probably it can be improved so that the first digit is not 0.

private void textbox_PreviewTextInput(object sender, TextCompositionEventArgs e)
        {
            if (!Char.IsDigit(e.Text, 0))
            {
                e.Handled = true;
            }
        }

I also have a code so that only one ',' can be entered, but I do not know how to redo it for 0.

if (!(Char.IsDigit(e.Text, 0) || (e.Text == ",") && (!TB1.Text.Contains(".") && TB1.Text.Length!=0))){
   e.Handled = true;
}
if ((e.Text == ",") && ((sender as TextBox).Text.IndexOf(',') > -1))
{
   e.Handled = true;
}

You could compose the new string and then query if it starts with zero

TextBox textBox = (TextBox)sender;
int caretIndex = textBox.CaretIndex;
string newText = textBox.Text.Substring(0, caretIndex) + e.Text + textBox.Text.Substring(caretIndex);
if (newText.StartsWith("0")) 
{
    e.Handled = true;
}