[DotNetDevelopment] general path

[Programmer]

string filename = "C:\\uo\\E.txt";
            long linecount = 0;
            using (StreamReader sr = new StreamReader(filename))
            {
                string line;
                while ((line = sr.ReadLine()) != null)
                {
                    linecount++;
                }
            }
            MessageBox.Show(linecount.ToString());

i want to give general path in string filename. like i would like to
count all .txt file records .

any ideas.

eg: string filename = "C:\\uo\\*.txt"  i need something like this