title: C# exception. File is being used by another process
body: <p>I'm playing around with C# and I encountered a problem.
  When I try to make a new file, the program breaks and says that the file is being used by another process. It's probably something stupid that I overlooked, but I cant figure it out!</p>
  
  <p>Here is my code:</p>
  
  <pre><code>using System;
  using System.IO;
  using System.Collections.Generic;
  using System.ComponentModel;
  using System.Data;
  using System.Drawing;
  using System.Linq;
  using System.Text;
  using System.Windows.Forms;
  
  namespace myNameSpace
  {
      public partial class MainWindow : Form
      {
          public static string folderPath = @"fullpath";
          public MainWindow()
          {
              InitializeComponent();
              StoredTb.Text = folderPath;
              String[] files = Directory.GetFiles(folderPath);
              foreach (string file in files)
                  myDropDown.Items.Add(Path.GetFileNameWithoutExtension(file));
          }
  
          private void myDropDown_SelectedIndexChanged(object sender, EventArgs e)
          {
              this.BeginInvoke(new MethodInvoker(myDropDown_invokedMethod));
          }
  
          private void myDropDown_invokedMethod()
          {
              string fullpath = MainWindow.folderPath + myDropDown.SelectedText + ".txt";
              StreamReader sr = new StreamReader(fullpath);
              NameTb.Text = myDropDown.SelectedText;
              DescriptionTb.Text = sr.ReadToEnd();
              sr.Close();
          }
  
          private void SaveBtn_Click(object sender, EventArgs e)
          {
              File.Create(NameTb.Text + ".txt");
              TextWriter tw = new StreamWriter(NameTb.Text + ".txt"); /* this is where the problem occurs */
              tw.WriteLine("The very first line!");
              tw.Close();
          }
      }
  }
  </code></pre>
  
  <p>Sorry for the long code snippet, but since I'm not sure where the problem originates from I had to include pretty much everything.</p>