Mobile Numbert Validation code as follows

Question

 Mobile Number textbox1;

Mobile Number should be 10 Digit validation

if (txt_mobile.Text.Length < 10)

     {

    LblErr.Text = "Enter Correct Mobile Number";

    return;

  }

Mobile Number start with 0 Validation

if (txt_mobile.Text.StartsWith("0"))

      {

     LblErr.Text = "Dont start with Mobile Number 0 ";

        return;

      }

i written  the two validation

But i want that two validation to be written in one condition(like one validtion in that both validation should satisfy)

how to do .

please give the code from my above code.