Upload.cs

public void LoopThroughExcel()
  {
  //getting datatable of excel rows by passing file name (from the form) and sheet name of excel
  DataTable InternalRecords = ConvertExcelToDataTable(ofdBrowseFile.FileName, "SheetName");
  //Looping through Excel records
  foreach (DataRow row in InternalRecords.Rows)
      {
      try
        {
        foreach (DataColumn dtCol in InternalRecords.Columns)
          {
          //Check for file path column
          if (dtCol.ColumnName.Contains("File Path"))
            {
              //get value of file path
              if (!string.IsNullOrEmpty(row[dtCol.ColumnName].ToString()))
              {
              //Call upload document method. Upload file is of type SharePoint.Client.File
                uploadFile = UploadDocument(row, fileName, oWeb, oList, row[dtCol.ColumnName].ToString());                                                    
              }
            }
          }
        }
      }
      
      //method to get datatable from excel
      public DataTable ConvertExcelToDataTable(string filename, string tabName)
        {
            DataTable dataTable = null;
            try
            {
                string sql = @"SELECT * FROM [" + tabName + "$]";

                using (OleDbConnection connection = new OleDbConnection("Provider=Microsoft.ACE.OLEDB.12.0;Data Source=" + filename + ";Extended Properties='Excel 12.0;IMEX=1;HDR=Yes'"))

                using (OleDbCommand command = new OleDbCommand(sql, connection))

                using (OleDbDataAdapter adapter = new OleDbDataAdapter(command))
                {
                    dataTable = new DataTable(); ;
                    adapter.Fill(dataTable);
                    return dataTable;
                }
            }

            catch (Exception ex)
            {
                
            }

            return dataTable;
        }
        
  //method to upload document
    public Microsoft.SharePoint.Client.File UploadDocument(DataRow row, string fileName, string filePath )
        {
        ListItem listItem = null;
        string siteurl = "siteurl";            
        ClientContext ctx = new ClientContext(siteurl);
        List libraryObj = ctx.Web.Lists.GetByTitle("libTitle");
        Microsoft.SharePoint.Client.File uploadFile = null;
            try
            {
                string DocumentPath = filePath.Trim();
                if (!System.IO.File.Exists(DocumentPath))
                {
                    throw new FileNotFoundException();
                }
                else
                {
                    System.IO.FileStream FileStream = System.IO.File.OpenRead(DocumentPath);
                    string DocFileName = System.IO.Path.GetFileName(DocumentPath);
                    ctx.Load(
                    libraryObj,
                    library => library.RootFolder.ServerRelativeUrl);
                    ctx.ExecuteQuery();
                    using (FileStream fs = System.IO.File.OpenRead(filename))
                    {
                    //upload file
                         Microsoft.SharePoint.Client.File.SaveBinaryDirect(ctx, libraryObj.RootFolder.ServerRelativeUrl + @"/" + DocFileName, fs, true);
                         uploadFile = ctx.Web.GetFileByServerRelativeUrl(libraryObj.RootFolder.ServerRelativeUrl + @"/" + DocFileName);
                         ctx.Load(uploadFile);
                         ctx.Load(uploadFile.ListItemAllFields);
                         ctx.ExecuteQuery();
                         listItem = uploadFile.ListItemAllFields;
                         ctx.ExecuteQuery();
                    }
                  }
                    if (new FileInfo(DocumentPath).Length == 0)
                        throw new Exception("File is empty");
                    //assign value to file's list item from Excel sheet. 
                    listItem["FieldName"] = row["FieldNameinExcel"].ToString().Trim();
                    //Similarly update other fields
                    listItem.Update();
                    ctx.ExecuteQuery();                    
                    uploadFile.CheckIn("Checking file in",CheckinType.MajorCheckIn);                    
                    ctx.ExecuteQuery();
                    return uploadFile;
                }
               catch (Exception ex)
               {
                throw;
               }
        }