// code for save dialog box

private void btnSaveFile_Click(object sender, System.EventArgs e)
		{
			saveFileDialog1.Title = "Specify Destination Filename";
			saveFileDialog1.Filter = "Text Files|*.txt";
			saveFileDialog1.FilterIndex = 1;
			saveFileDialog1.OverwritePrompt = true;

			if (saveFileDialog1.ShowDialog() != DialogResult.Cancel)
				txtDestination.Text = saveFileDialog1.FileName;
		}

// create a file stream, where "c:\\testing.txt" is the file path
			System.IO.FileStream fs = new System.IO.FileStream("c:\\testing.txt", System.IO.FileMode.OpenOrCreate, System.IO.FileAccess.Write, System.IO.FileShare.ReadWrite);

			// create a stream writer
			System.IO.StreamWriter sw = new System.IO.StreamWriter(fs, System.Text.Encoding.ASCII);

			// write to file (buffer), where textbox1 is your text box
			sw.Write(txtDestination.Text);

			// flush buffer (so the text really goes into the file)
			sw.Flush();

			// close stream writer and file
			sw.Close();fs.Close();