C# get Property method not found

Question

I have a project (class library project) with target version .NET Framework 3.5. I am accessing a string (SplittedPermanentAddressAsString) using get method

 if (!Util.isEmpty(cardDetails.SplittedPermanentAddressAsString))
            {
                permanentAddressStr += cardDetails.SplittedPermanentAddressAsString;
            }

and here is the Property

 public string SplittedPermanentAddressAsString
    {
        get
        {
            if (PermanentAddress != null)
            {
                return PermanentAddress.SplittedFullAdrsEn;
            }
            else
            {
                return "";
            }
        }
    }

When i run the application, i find following error

"Method not found: 'System.String HSDLServerAdminLib.Entity.Card.CardDetails.get_SplittedPermanentAddressAsString()'. Stack Trace: at HSDLAdminPortal.ServiceImpl.Card.CardViewDetailImpl.viewDetailInfo(Object view, Object res) at HSDLAdminPortal.Controller.Card.CardDetailsController.worker_RunWorkerCompleted(Object sender, RunWorkerCompletedEventArgs e)