Need to validate textbox for a value, and a value between two numbers. Throwing an error : So i have a textbox which needs validation upon clicking my "Add" button. 
The first check works fine when the other two checks aren't in the code. The bottom two checks are fine if I enter a value into the textbox. However when I have all three checks, when there isn't a value, the program throws back an error saying "input string was not in correct format". 

<!-- begin snippet: js hide: false console: true babel: false -->

<!-- language: lang-js -->

     if (txtAge.Text == "")
                {
                    message += "<br>Please fill in your Age.</br>";
                }
                if (Convert.ToInt32(txtAge.Text) > 120)
                {
                    message += "<br>Age cannot be greater than 120</br>";
                }
                if (Convert.ToInt32(txtAge.Text) < 6)
                {
                    message += "<br>Age cannot be less than 6</br>";
                }

<!-- end snippet -->

