Question

I am using the following code to read and combine number of texts in one string:

            foreach (string path in filePaths)
            {


                StreamReader singfile = new StreamReader(path);

                string  file_text = singfile.ReadToEnd();
                combinetexts += file_text + "\n";

                fs.Close();

            }

and as I know, the string combinetexts will copy n times as much as the number of filepaths. is it possible the to do that orcedure using string builder ? I tried but it doesn’t.
thanks in advance.

Answer 1

Here’s a short LINQ way of doing it:

string result = string.Join("\n", filePaths.Select(x => File.ReadAllText(x)));

Or with C# 4 (which has better handling of type inference wrt method group conversions):

string result = string.Join("\n", filePaths.Select(File.ReadAllText));

If you’re using .NET 3.5 you’ll need to create an array of the strings, as string.Join didn’t have as many overloads then:

string result = string.Join("\n", filePaths.Select(x => File.ReadAllText(x))
                                           .ToArray());

This has the disadvantage of reading all of all the files before performing the concatenation, admittedly – but it’s still better than the repeated concatenation in the original code. It might also be more efficient than using StringBuilder – it depends on the string.Join implementation.

See my article on StringBuilder for why the original code is really inefficient.

EDIT: Note that this does not include a trailing \n at the end. If you really want to add that, you can 🙂