C# Regular Expression Replace and Add to End

Question

I'm trying to create a find/replace regular expression in C# to find strings that start with -i, then contain any number of digits (no spaces) and then replace the -i with an empty string, but also add 2 spaces to the end to make up for removing the -i (it is a fix length file).

Right now, I am doing this to replace the text without adding the spaces at the end:

File.WriteAllText(textBox1.Text, Regex.Replace(File.ReadAllText(textBox1.Text), @"[-i]", ""));

An example line in the file is:

-i3598            00015

And I want the result to be:

3598              00015

Notice that the total length is the same before and after.

Thanks in advance!

Answer 1

Please try the following. It uses Regular Expressions Substitutions in the replacement pattern.

File.WriteAllText(
    textBox1.Text, 
    Regex.Replace(
        File.ReadAllText(textBox1.Text), 
        @"-i(\d+)", 
        "$1  "));