The Substring method is used to grab characters from a string of text. For
example, suppose you were testing an email address. You want to test the last
four characters to see they are .com. You can use Substring to return just those
four characters, and see what’s in them. (You can also use IndexOf to achieve
the same result.)
Substring has this syntax:
the_word.Substring( start_position )
So the word you want to grab characters from goes first, followed by the Substring
method. In between the round brackets, you have to tell C# where in the word
to start grabbing characters from.
But Substring can also take a second parameter:
the_word.Substring( start_position, num_of_chars_to_grab
The second parameter is how many characters you want to grab. If you leave
this out, C# will grab all the characters to the end of your word. Here’s some
code to try, with a new button:
We’re using Substring with two parameters (5, 4). But since we’re
grabbing to the end of the word, we could have left out the , 4 at the end.
To test it out, change the firstname.lastname@example.org to email@example.com. Run your programme
and you should see “Bad Email Address”. Change it back and the email
address will be OK.
Use Substring to check that an email address ends in .co.uk. For the email address
to check, use firstname.lastname@example.org.
Kaynak : https://www.homeandlearn.co.uk/csharp/csharp_s8p8.html ‘sitesinden alıntı