c# - Read and write to a file in the same stream

Question

I'm trying to read and write to the same file in a way such that no other program can access the file in between:

  FileStream fs = new FileStream(filePath, FileMode.OpenOrCreate, FileAccess.ReadWrite, FileShare.None);               
  StreamReader sr = new StreamReader(fs);
  StreamWriter sw = new StreamWriter(fs);
  newString = sr.ReadToEnd() + "somethingNew";
  sw.Write(newString);
  fs.Close();

The file is never written to. If I debug I can see that the reader manages to fetch the contents of the file, but the writer does not seem to be able to write to the file. Nothing happens.

I've been looking at this question which seems to be the same as mine. However I'm not able to get it to work.

Answer 1

Just Flush your changes to file, Have sw.Flush(); before closing the stream. like:

string filePath = "test.txt";
FileStream fs = new FileStream(filePath, FileMode.OpenOrCreate, FileAccess.ReadWrite, FileShare.None);
StreamReader sr = new StreamReader(fs);
StreamWriter sw = new StreamWriter(fs);
newString = sr.ReadToEnd() + "somethingNew";
sw.Write(newString);
sw.Flush(); //HERE
fs.Close();

You may see this post simultaneous read-write a file in C# (open multiple streams for reading and writing)