In some cases we need to add documents to the doument library  programatically, the  code snippet below demonstrates how to add a document to the document library .

using (SPSite objSite = new SPSite("urlAddress"))
{
       objSite.AllowUnsafeUpdates = true;

        using (SPWeb oSPWeb = objSite.OpenWeb())
        {
               oSPWeb.AllowUnsafeUpdates = true;
  
              //Test1 is the document library

               SPList docLibrary = oSPWeb.Lists["Test1"];

                using (FileStream fs = File.OpenRead(FullPath))
                {
                          //Name is the name of the file
                         SPFile file = oSPWeb.Files.Add(oSPWeb.Url.ToString() + "/" + docLibrary.Title.ToString()
                                                                  + "/" + Name, fs);
                         file.Update();
                 }

                 docLibrary.Update();

                 oSPWeb.AllowUnsafeUpdates = false;
         }

         objSite.AllowUnsafeUpdates = false;
                  
}