Question

can I do this without looping through the whole list?

List<string> responseLines = new List<string>();

the list is then filled with around 300 lines of text.

next I want to search the list and create a second list of all lines that either start with “abc” or contain “xyz”.

I know I can do a for each but is there a better / faster way?

Answer 1

You could use LINQ. This is no different performance-wise to using foreach — that’s pretty much what it does behind the scenes — but you might prefer the syntax:

var query = responseLines.Where(s => s.StartsWith("abc") || s.Contains("xyz"))
                         .ToList();

(If you’re happy dealing with an IEnumerable<string> rather than List<string> then you can omit the final ToList call.)