open a streamwriter/reader

[michaeldebruin]

I am trying to make a program which acts just a bit like a database. The only problem yet is that I had problems with my streamwriters and readers. It seems that my streamwriter only wants to write a string in a txt file when I say

sw.Close();

, but how can I open the stream again?

[GaryTexmo]

Only close the stream when you're done with it. That said, if you want to reopen it, just do it the same way you did in the first place.

[adriancs]

Open, Read and Close a file:

string FileName = @"C:\myFileName.txt";
string[] stringArray = null;

if (File.Exists(FileName))
{
    stringArray = File.ReadAllLines(FileName);
    foreach (string line in stringArray)
    {
        // Do something here...
    }
}
else
{
    MessageBox.Show("File Not Exists");
}

Open, Write and Close a file:

string filePath = @"C:\";
string fileName = "myFileName.txt";
string[] stringArray = null; // replace this with your data
if (Directory.Exists(filePath))
    File.WriteAllLines(filePath + fileName, stringArray, Encoding.UTF8);
else
    MessageBox.Show("The directory is not exist");

[Plater]

If you are only seeing your data written on the .Close() then I would guess you need to call Flush().
You should be able to keep the file open(if that is what you want) and keep writing, calling Flush() when required

[bvrwoo]

You must keep the file open while writing because when you close all operations are processed and then the file is close and unmanaged resources are destroyed.

using (TextWriter tw = new StreamWriter(file))
{
    foreach (string s in strings)
        tw.WriteLine(s);//or whatever you are saving as string
}

you don't need to call on tw.Close() because it is in a 'using' block which you can use for any class/struct which inherits the IDisposable interface.