How to increment a Numeric String by 1

If you want to do that in C#, i'd suggest to use String.Substring[^] method to get numeric part of OptionNumber. Now, use Int32.Parse[^] method to convert string-number to its proper numeric value.

Try!

I really wouldn't advice doing this. If you need a growing sequence number, store the number separately. Have a separate column containing the number and increment it by one whenever needed. Based on your example the prefix "OP" looks like a static one but if it isn't then store the prefix in another column. But the key is to have the number in a separate, single, numeric column. This will make your life much easier in the future.

To go a bit further, if the number is used to uniquely identify a record and you use a database, I would suggest letting the database to generate the next value for you. If you do it in client side code, and you store the records in a database, there is always a chance that two client applications generate the same number and you would have a collision.

Try below code:

// Input op0021(value of 'OptionNumber' column)

string num = set.Tables[0].Rows[(set.Tables[0].Rows.Count) - 1]["OptionNumber"].ToString();
            num = num.Substring(2, num.Length - 2);
            int test = Convert.ToInt32(num) + 1;
            string test2 = "op" + Convert.ToString(test).PadLeft(num.Length, '0');

// Output: op0022