Adding file in SharePoint document Library using sandbox solution

Question

 Why I am Missing Uploaded File name In Post back & am unable to add debugger give me solution thanks in advance
Below is my sample code
protected void btnsubmit_Click1(object sender, EventArgs e)
            try
                        //upload Image
                        web.AllowUnsafeUpdates = true;
                        Boolean replaceexistingfile = true;
                        if (Filephoto.HasFile)
                            Stream fStream = Filephoto.PostedFile.InputStream;
                            byte[] contents = new byte[fStream.Length];
                            fStream.Read(contents, 0, (int)fStream.Length);
                            fStream.Close();
                            string FileName = Filephoto.FileName;
                            string destUrl = SPContext.Current.Web.Url + DocumentLibName + FileName;
                             web.Files.Add(destUrl, contents, replaceexistingfile);
                            SPFile file = web.Lists[DocumentLibName].RootFolder.Files.Add(FileName, contents, replaceexistingfile);
                            lblliteral.Text = file.ToString();
                            SPFieldLookupValue value = new SPFieldLookupValue(listitem.ID, listitem["EmployeeCode"].ToString());
                            file.Item["EmployeeCode"] = value.ToString();
                            file.Item.Update();
                        else
                            //throw new FileNotFoundException("File Not Found");
                            string FileName = "nofile";
                            lblliteral.Text = FileName + "filepload" + FilePassport.FileName + " : " + FilePan.FileName;
                        web.AllowUnsafeUpdates = false;
            catch (Exception ex)
              //  Page.Response.Write(ex.Message);
                string FileName = ex.Message;
                lblliteral.Text = FileName;
                                                        

Answer 1

Hi,
We can put into the Session, the code snippet for your reference:
//If first time page is submitted and we have file in FileUpload control but not in session
// Store the values to SEssion Object
if (Session["FileUpload1"] == null && FileUpload1.HasFile)
Session["FileUpload1"] = FileUpload1;
Label1.Text = FileUpload1.FileName;
// Next time submit and Session has values but FileUpload is Blank
// Return the values from session to FileUpload
else if (Session["FileUpload1"] != null && (! FileUpload1.HasFile))
FileUpload1 = (FileUpload) Session["FileUpload1"];
Label1.Text = FileUpload1.FileName;
// Now there could be another sictution when Session has File but user want to change the file
// In this case we have to change the file in session object
else if (FileUpload1.HasFile)
Session["FileUpload1"] = FileUpload1;
Label1.Text = FileUpload1.FileName;
More information about the similar issue:
http://www.codeproject.com/Tips/101834/How-to-Maintain-FileUpload-Control-s-State-after-P
If you want to upload file into document library, here is another option for your reference:
http://purtuga.github.io/SPWidgets/
Best Regards
Dennis Guo
TechNet Community Support