C#! HELP Please!

I rellly need help with c#.

Okay i was going sort words from a text file and then write the sorted version into the text file. Everything works but 200 first lines are only blankspaces.

How can i remove them for the string?

Ive tried

string out_put = in_put.trim();

string out_put = Regex.Replace(in_put, " ", " ");

Anyone who can help?

if (out_put.Length == 0) continue;