Seek Function in C#

[vineeta]

Hi All,

I was trying to overwrite the data in a file.
But seek function is not working as i expecting.
My code is here:

public void createfile()
{
FileStream fs = new FileStream(@"C:\Documents and Settings\MyText.txt", FileMode.Create, FileAccess.Write);
string text = "Welcome to DotNet Forum";
StreamWriter sw = new StreamWriter(fs);
sw.WriteLine(text);
sw.Write("File ended");
sw.Close();
fs.Close();
}
public void updatefile()
{
FileStream fs = new FileStream(@"C:\Documents and Settings\MyText.txt", FileMode.Open, FileAccess.ReadWrite);
StreamWriter sw = new StreamWriter(fs);
sw.Write(57);
sw.BaseStream.Seek(8, SeekOrigin.Begin);
sw.Write(22);
sw.Close();
fs.Close();
}

According to my expectation it should return "57lcome 22 DotNet Forum" but it is returning "Welcome 5722otNet Forum";

Seek function has called before sw.Write().
Can anyone help me on this?

Thanks
Vineeta

[Plater]

Oh delayed writes you are a fical mistress.
It happens because the data hasn't actually been written to the underlying stream yet by the time you call the seek function.
(Also your example you forgot to put quotes around your strings)

public void updatefile()
{
   FileStream fs = new FileStream(@"C:\MyText.txt", FileMode.Open, FileAccess.ReadWrite);
   StreamWriter sw = new StreamWriter(fs);
   sw.Write("57");
   sw.Flush();
   sw.BaseStream.Seek(8, SeekOrigin.Begin);
   sw.Write("22");
   sw.Close();
   fs.Close();
}
 

[vineeta]

Thanks Plater,

actually write is a overloaded function of StreamWriter and it takes everything as text so quotes are not needed. I have added some delay also

sw.Write("57");
Thread.Sleep(10000);
sw.BaseStream.Seek(8, SeekOrigin.Begin);
sw.Write("22");

Still it is behaving as earlier

-Vineeta

[r035198x]

Try calling streamreader.DiscardBufferedData(); between the writes.

[Plater]

You shouldn't need the delay if you use flush. There is no garuntee that the delay will *always* be long enough to do the write. It could be waaay to long, or it could be just a bit too short, depending on how much data is to write.
Using the flush forces the application to wait until the data is written, and only the amount of time it takes to write the data.