reading record quick enough, i speed up?

this proceed i review file:

    open stationary twine readfile(string path)
    {
        stringbuilder stringfromfile = new stringbuilder();
        streamreader sr;
        twine s;
        sr = file.opentext(path);
        s = sr.readline();
        while (s != null)
        {
            stringfromfile.append(sr.readline());
        }
        sr.close();
        relapse stringfromfile.tostring();
    }

the problem enlarged (the .txt record 2.5 megs). took over 5 minutes. there improved way?

solution taken

    open stationary twine readfile(string path)
    {

       relapse file.readalltext(path);

    }

took reduction 1 second... :)