Delete the last instance of a certain string from a text file without changing the other instances of the string

Question

Hello,

I have a C# program where I am using a lot of RegEx.Replace to replace text in my text file.

Here is my problem.

In my text file, I have a code such as "M6T1". This code is listed in numerous places in the text file.

However, I only want to delete it from the bottom (last instance) in the text file. There will always be a "M6T1" at the bottom of the text file, but it is not always the last line. It could be the 3rd line from the bottom, the 5th line from the bottom etc.

I only want to get rid of the last instance of "M6T1" so RegEx.Replace won't work here. I don't want to interfer with the other "M6T1"'s in the other locations in the text file.

Can someone please give me a solution to this problem?

Thanks

Answer 1

var needle = "M6T1";
var ix = str.LastIndexOf(needle);
str = str.Substring(0, ix) + str.Substring(ix + needle.Length);