Remove blank lines from .txt file

            FileStream fs = new FileStream("test.txt", FileMode.Open,FileAccess.Read);
            StreamReader sr = new StreamReader(fs);
            string data = sr.ReadToEnd().Replace("\r\n\r\n", "\r\n");
            sr.Close();
            fs.Close();

            File.Delete("test.txt");

            FileStream fs1 = new FileStream("test.txt", FileMode.OpenOrCreate, FileAccess.Write);            
            StreamWriter sw = new StreamWriter(fs1);            
            sw.Write(data);
            sw.Close();
            fs1.Close();

Simple:

            string data = File.ReadAllText("test.txt").Replace("\r\n\r\n", "\r\n");            
            File.Delete("test.txt");
            File.WriteAllText("test.txt", data);

The above examples have one major flaw: if you have, say, three blank lines one after other the code will convert it to two lines, four - to two, five - to thre, etc. So you may need to run the procedure again - not very clever...

I use different pproach - I read file to a list and add only non-blank lines (you may also add trim() method to remove lines of spaces). Code is simple enough:

        private void button2_Click(object sender, EventArgs e)
        {
            List<string> lines  = new List<string>();

            // Read file to list
            StreamReader sr = File.OpenText("C:\\atest.txt");
            string input = null;
            while ((input = sr.ReadLine()) != null)
            {
                if (input.Length > 0)
                {
                    lines.Add(input);
                }
                Console.WriteLine(input);
            }
            sr.Close();


            // Write file
            StreamWriter sw = new StreamWriter("C:\\atest2.txt");
            foreach (string line in lines)
            {
                sw.WriteLine(line);
            }
            sw.Close();
        }

By the way, my test file (atest.txt):

"
aaa

bbb


ccc



ddd




eee





fff






gggg

.
"

Run my code and compare to result of running previous code.

anarki_jimbel, i dint find any flaw in my code... i do know what u r trying to do... After testing only i used to post my code.... It works fine

The goal is to remove blank lines, isn't it?

Your code (accepted one) gives the following result with my test file"
"
aaa
bbb

ccc

ddd


eee


fff



gggg
.
"

So your code removes some blank lines but not all! That's why I posted my test file content - for you to test. So my improvement (assisted solution) does it's job much better.Try to prove opposite. I tried the last version of your code only, just in case.

 I don't like my solution from the point of performance. By the way, for Alan, To make my code more efficient for big files (if you need) use StringBuffer class to build output, and returm stringbuffer object. toString().