SSIS脚本模糊错误“对象引用未设置为对象的实例”

Question

我正在研究一个SSIS脚本，一切都通过Visual Studio很顺利，但是当我执行时我得到：

  

[FTP脚本任务]错误：错误：对象引用未设置为   对象的实例。

这是我正在运行的代码。我做错了什么？

    public void Main()
    {
        try            
        {                
            // Get the ftp connection from the Connection Managers collection                
            ConnectionManager ftpServer = Dts.Connections["SFTP_Connection"];                 

            // Create a FTP connection object and us the credentials of connection manager                
            FtpClientConnection SFTP_Connection = new FtpClientConnection(ftpServer.AcquireConnection(null));

            // Open the connection                
            SFTP_Connection.Connect();                 

            // Set work folder with the value of the variable                
            SFTP_Connection.SetWorkingDirectory(Dts.Variables["FtpWorkingDirectory"].Value.ToString());

            // Create StringArrays for filenames and folders                
            // The folderNames aren't used, but is mandatory                
            // for the next method.                
            String[] fileNames;                
            String[] folderNames;                 

            // Get a directory listing and fill the StringArray variables                
            SFTP_Connection.GetListing(out folderNames, out fileNames);

            SFTP_Connection.ReceiveFiles(fileNames, "\\\\server\\e$\\INFORMATICA_INCOMING\\VERSADEX\\CAD\\work\\Test\\", false, false);                 

            // Close connection                
            SFTP_Connection.Close();                 

            // Close Script Task, set result to success                
            Dts.TaskResult = (int)ScriptResults.Success;            
        }            

        catch (Exception ex)            
        {                
            // Fire error and set result to failure                
            Dts.Events.FireError(0, "FTP Script Task", "Error: " + ex.Message, string.Empty, 0);
            Dts.TaskResult = (int)ScriptResults.Failure;            
        }
    }