Question

i like to read check the text has multi line or single line and then i am going to read that multi lines and convert into single line how can i do this?

Answer 1

You really do not need to check as File.ReadAllLines() will always return a string array regardless of the number of lines. You can leverage that behavior and simply join the returned array with your separator of choice.

string singleLine = string.Join(" ", File.ReadAllLines("filepath"));