sharepoint site restore error unable to open content database

sharepoint site restore error unable to open content database. Error at restore the .bak file

Run the sharepoint designer workflow by c# code in .net

 Running the Designer workflow by c# code
 =========================================================
SPSecurity.RunWithElevatedPrivileges(delegate
            {
                using (SPSite osite = new SPSite(SPContext.Current.Web.Url))
                using (SPWeb oweb = osite.OpenWeb())
                {
                    osite.AllowUnsafeUpdates = true;
                    SPList oListSecScore = oweb.Lists.TryGetList("Active Appraisals");
                    SPListItemCollection oListColl = oListSecScore.Items;
                    SPListItem oListItem = oListColl.Add();

                    oListItem["Title"] = "Appraisal_" + appraisalyr + "_" + ddlStaffId.SelectedValue;
                    oListItem["SubmitterCmnt1"] = txtSubmitterCmt.Text.Trim();

                    SPFieldUserValueCollection usercollection = new SPFieldUserValueCollection();
                    SPFieldUserValue usertoadd = General.ConvertLoginAccount(pendinguser);
                    usercollection.Add(usertoadd);
                    oListItem["PendingUser"] = usercollection;

                    SPFieldUserValueCollection userstaff = new SPFieldUserValueCollection();
                    SPFieldUserValue useraddstaff = General.ConvertLoginAccount(ddlStaffId.SelectedValue);
                    userstaff.Add(useraddstaff);
                    oListItem["Staff"] = userstaff;                
                 
                    oListItem.Update();
                    SPWorkflowAssociationCollection associationCollection = oListSecScore.WorkflowAssociations;
                    foreach (SPWorkflowAssociation association in associationCollection)
                    {
                        if (association.Name == "PendingUserWF")
                        {
                            association.AutoStartChange = true;
                            association.AutoStartCreate = true;
                            association.AssociationData = String.Empty;
                            osite.WorkflowManager.StartWorkflow(oListItem, association, association.AssociationData);
                        }
                    }
                    osite.AllowUnsafeUpdates = false;

                }
            });