Lets say I got this AB_1.2.3.112211 in a property
What I want is to exchange the first "." to a "_"
So it becomes AB_1_2.3.112211 The two first characters could be longer fx ABCD_1.2.3.112211 but it should still be the output ABCD_1_2.3.112211
Is there a way to do this in msbuild task?
If the input strings are always as you show them, i.e. the first "." to replace comes after an underscore followed by a number you can use a property function and use C#'s static Regex.Replace method:
If the use case is more complicated there are other options: