How Convert TextBox Value in integer?

Have a look at the below link; You will get a complete idea:

https://www.codeproject.com/Tips/845439/Difference-between-int-Parse-Convert-ToInt-and-int

http://dailydotnettips.com/2016/01/16/back-to-basic-difference-between-int-parse-and-int-tryparse/

You can Use the int.TryParse method.

If it successfully parses it will return true, and the out result will have its value as an integer.

Code will work fine if the texbox value is an integer or else it will throw an error "Input string was not in a correct format"