Uploading Multiple Files to SharePoint Document Library using .NET CSOM

Prerequisites

We need to have the  AJAX Control toolkit installed.

1. Create an ASP.NET web application.
   
   
   
   
2. Add SharePoint DLL References. These references can be found in “C:\Program Files\Common Files\Microsoft shared\Web Server Extensions\15\ISAPI”.
   
   In order to have this dll you need to install SharePoint Client SDK “https://www.microsoft.com/en-us/download/details.aspx?id=35585”
   
   
   
   
3. Now on your web form, you need to drag AjaxFileUpload Controland ScriptManager.
   
   
   
   
4. Now on OnUploadComplete create an Event.
   
   
   
   And paste the following code.
   

   protectedvoidOnUploadComplete(object sender, AjaxFileUploadEventArgs e)
   {
       try
       {
           //gets the filename
           stringfileName = Path.GetFileName(e.FileName);
           //gets the temporary location of file and ID of folder where files are stored in temporary folder
           string path = Path.Combine(Path.GetTempPath(), "_AjaxFileUpload", e.FileId);
           //store the path in Sessio
           Session["FileDirectory"] = path;
           //get the site
           ClientContext context = newClientContext(siteUrl);
           //get the web object
           WeboWebsite = context.Web;
           context.Load(oWebsite);
           //execute the web object
           context.ExecuteQuery();
           //get the current list
           ListCurrentList = context.Web.Lists.GetByTitle(listName);
           context.Load(CurrentList.RootFolder);
           context.ExecuteQuery();
           //form the url to get the entire path of file like D://folder/test.txt
           StringfileURL = (path + "\\" + fileName);
           using(FileStreamfileStream = newFileStream(fileURL, FileMode.Open))
           Microsoft.SharePoint.Client.File.SaveBinaryDirect(context, CurrentList.RootFolder.ServerRelativeUrl.ToString() + "/" + e.FileName, fileStream, true);
       }
       catch (Exception ex)
       {
           lblError.Text = ex.ToString();
           lblError.BackColor = System.Drawing.Color.Red;
           lblError.ForeColor = System.Drawing.Color.White;
       }
       finally
       {
           //delete files from temp folder
           e.DeleteTemporaryData();
       }
   }

5. Now run the application.
   
   
   
   
   
   
   Files are now uploaded to SharePoint.