Uploading Only Text Files using FileUpload Control using Required Validation

Uploading only text files using FileUpload Control using required validation.

Introduction

Mentioned code is for uploading only text files using file upload control, many a times even a file which is not of extension .txt is uploaded in the database. Used a validation in the below code which will help the developers to allow only text files to be uploaded without special characters.

protected void UploadButton_Click(object sender, EventArgs e)
{
    if (FileUploadControl.PostedFile != null && FileUploadControl.PostedFile.FileName != "" && FileUploadControl.PostedFile.ContentLength >
0)
    {
        try
        {
           System.IO.BinaryReader r = new System.IO.BinaryReader(FileUploadControl.PostedFile.InputStream);
           string fileclass = "";
           byte buffer;
           try
           {
               buffer = r.ReadByte();
               fileclass = buffer.ToString();
               buffer = r.ReadByte();
               fileclass += buffer.ToString();
            }
            catch (Exception ex)
            {
               Message.ClearMessage();
               Message.ShowMessage(ex.Message.ToString(), AppMessages.MessageType.Error);
               return;
            }
            if (!(fileclass == "8269" || fileclass == "4948"))
            {
               Message.ClearMessage();
               Message.ShowMessage("The upload file must be in plain text format.", AppMessages.MessageType.Error);
               r.Close();
               return;
           }
           FileUploaded fileUpload = new FileUploaded();
           filename = Path.GetFileName(FileUploadControl.FileName);
           string FileUploadLocation = Server.MapPath("~/") + "UserData//" + filename;
           FileUploadControl.SaveAs(FileUploadLocation);
           r.Close();
           using (FileStream fs = new FileStream(FileUploadLocation, FileMode.Open, FileAccess.Read))
           {
              byte[] imageData = new Byte[fs.Length];
              fs.Read(imageData, 0, System.Convert.ToInt32(fs.Length));
              fs.Close();
              fileUpload.Fileobject = imageData;
           }
           string text = string.Empty;
           using (System.IO.StreamReader file = new System.IO.StreamReader(FileUploadLocation))
           {A
             text = file.ReadToEnd();
           }
           Regex objAlphaPattern = new Regex(@"^[a-zA-Z0-9|-]*$");
           text = text.Replace("\r\n", "").Replace("\n", "").Replace("\r", "");
           if (!(objAlphaPattern.IsMatch(text)))
           {
              File.Delete(FileUploadLocation);
              Message.ClearMessage();
              Message.ShowMessage("The upload file contains special characters.", AppMessages.MessageType.Error);
              return;
           }
           File.Delete(FileUploadLocation);
           fileUpload.Filename = filename;
       }
       catch (Exception ex)
       {
           Message.ClearMessage();
           Message.ShowMessage(ex.Message.ToString(), AppMessages.MessageType.Error);
       }
    }
}