Downloading attachment from Sharepoint List: object reference not set to instance of an Object error

Question

Hello,

I am using the following code for downloading attachment from Sharepoint 2007 List.
public static string downloadDoc(string listName, string ListItemID)
        {
            string filepath = "";
            try
            {
                AEPEx_MOSS.Lists ls = new AEPEx_MOSS.Lists();
                //ls.Credentials = System.Net.CredentialCache.DefaultCredentials;
                string MOSSWSUser = Microsoft.SSO.Utility.SSOConfigHelper.Read("AEPEx_CarrierInterface", "MOSSWSUserID");
                string MOSSWSPWD = Microsoft.SSO.Utility.SSOConfigHelper.Read("AEPEx_CarrierInterface", "MOSSWSUserPWD");
                string MOSSWSDomain = Microsoft.SSO.Utility.SSOConfigHelper.Read("AEPEx_CarrierInterface", "MOSSWSUserDomain");

                ls.PreAuthenticate = false;
                System.Net.NetworkCredential cred = default(System.Net.NetworkCredential);
                cred = new System.Net.NetworkCredential(MOSSWSUser, MOSSWSPWD, MOSSWSDomain);
                ls.Credentials = cred;
                SPSecurity.RunWithElevatedPrivileges(delegate()
                {
                    XmlNode ra = default(XmlNode);
                    ra = ls.GetAttachmentCollection(listName, ListItemID);
                    string url = ra.InnerText;
                    SPSite site = new SPSite(Microsoft.SSO.Utility.SSOConfigHelper.Read("AEPEx_CarrierInterface", "LIST_URL"));
                    SPWeb web = site.OpenWeb();
                    SPFile list = web.GetFile(url);
                    string fn = list.Name;
                    string guid = null;
                    guid = System.Guid.NewGuid().ToString();
                    if (!Directory.Exists(Microsoft.SSO.Utility.SSOConfigHelper.Read("AEPEx_CarrierInterface", "MOSSAttachmentPath") + guid))
                    {
                        Directory.CreateDirectory(Microsoft.SSO.Utility.SSOConfigHelper.Read("AEPEx_CarrierInterface", "MOSSAttachmentPath") + guid);
                        byte[] b = list.OpenBinary();
                        FileStream s = System.IO.File.Create(Microsoft.SSO.Utility.SSOConfigHelper.Read("AEPEx_CarrierInterface", "MOSSAttachmentPath") + guid + "\\" + list.Name);
                        filepath = Microsoft.SSO.Utility.SSOConfigHelper.Read("AEPEx_CarrierInterface", "MOSSAttachmentPath") + guid + "\\" + list.Name;
                        s.Write(b, 0, b.Length);
                        s.Dispose();
                        s.Close();
                    }
                }
                );
            }
            catch (Exception ex)
            {
                AEPEx.Integration.BizTalk.CommonUtilities.Logger.WriteError_Filenet("Exception getting Attachment " + ex.Message, EventLogEntryType.Error);

            }
            return filepath;
        }

I am getting an error:"Object reference not set to Instance of an object" error.
When I run this code from a WIndows app, the ATtachment is getting downloaded properly. However when i run this code by adding reference to a Biztalk APp, I am getting the error,at the line when the new SP Site is getting created. I have searched all over the internet without any solution.

Answer 1

Does the account that run Biztalk app runs under has rights in SharePoint?  The best solution would be to create a custom web service with this functionality and get Biztalk to call it.

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My SharePoint Blog - http://www.davehunter.co.uk/blog

Answer 2

How do I go about creating a custom WS to do this?Please suggest.Also how will creating a WS resolve the security issue.

Answer 3

Hello, I have created a web service for downloading the attachment from Sharepoint.I have set it to run under a user which is an Admin for the MOSS app. However I still get this error: Exception getting Attachment The Web application at http://:1002/_vti_bin/lists.asmx could not be found. Verify that you have typed the URL correctly. If the URL should be serving existing content, the system administrator may need to add a new request URL mapping to the intended application. Please suggest.

Answer 4

Hello,
I was able to make the WS work. The way to do it is to share the same Application pool for the web service as of the Sharepoint Shared Service.