no System.IO.File.ReadLines(file).Count() in .Net 4?

Question

I am trying to read the number of lines of a file I found here (stackoverflow) that the best way to read the number of lines in a large file is by using the following code:

int count = System.IO.File.ReadLines(file).Count();

However, I can't make it compile. Does any know what is the problem?

Error 5 'System.Collections.Generic.IEnumerable<string>' does not contain a definition for 'Count' and no extension method 'Count' accepting a first argument of type 'System.Collections.Generic.IEnumerable<string>' could be found (are you missing a using directive or an assembly reference?)

Thanks, Eyal

Answer 1

Count<T>() is an extension method for objects of IEnumerable<T>. Try adding a using statement for the namespace System.Linq.

Answer 2

Could you do:

int count = File.ReadAllLines(@"C:\filepath\file.txt").Length;

EDIT: As pointed out in the comments, this could (will) perform badly for large files. For a similar question with more detailed explanation why, view Determine the number of lines within a text file