title: open txt file by using OpenFileDialog in c#
body: <p>i write the following code to open txt file     </p>
  
  <pre><code>private void button1_Click(object sender, EventArgs e)
  {
      try
      {
          OpenFileDialog reader = new OpenFileDialog();
  
          reader.Filter = "txt files (*.txt)|*.txt";
          // reader.Title = "";
          reader.ShowDialog();
          rtb1.LoadFile(reader.FileName);
      }
      catch(Exception ex)
      {
          MessageBox.Show(ex.Message);
      }
  }      
  </code></pre>
  
  <p>but this code is give the following error:<br>
  <strong>Error:</strong><br>
      File format is not valid</p>