/// <summary>
        /// This is the method that actually does the work.
        /// </summary>
        /// <param name="DA">The DA object can be used to retrieve data from input parameters and
        /// to store data in output parameters.</param>

        protected override void SolveInstance(IGH_DataAccess DA)
        {
            // First, we need to retrieve all data from the input parameters.
            // Then we need to access the input parameters individually.
            // When data cannot be extracted from a parameter, we should abort this method.
            if (!DA.GetDataList <Dlubal.RFEM5.Line>(0, rfemLinesInput))
            {
                return;
            }
            DA.GetData(1, ref sectionIdInput);
            DA.GetData(2, ref materialIdInput);
            if (!DA.GetData(3, ref rfemHingeStartInput))
            {
                rfemHingeStartInput.No = -1;
            }
            if (!DA.GetData(4, ref rfemHingeEndInput))
            {
                rfemHingeEndInput.No = -1;
            }
            DA.GetData(5, ref rotationInput); //assignment of rotation angle via  Dlubal RFEM API appears not to be working
            DA.GetData(6, ref commentsInput);
            DA.GetData(7, ref run);

            // The actual functionality will be in a method defined below. This is where we run it
            if (run == true)
            {
                //clears and resets all output parameters.
                // this is done to ensure that if function is repeadedly run, then parameters are re-read and redefined
                RfemMemberList.Clear();
                writeSuccess = false;

                //runs the method for creating RFEM memebers
                RfemMemberList = CreateRfemMembers(rfemLinesInput, sectionIdInput, materialIdInput, rfemHingeStartInput, rfemHingeEndInput, rotationInput, commentsInput);
                DA.SetData(1, writeSuccess);
            }
            else
            {
                // if "run" is set to false, then also the output parameter "success" is set to false
                // this ensures that as soon as "run" toogle is set "false", it automatically updates output.
                DA.SetData(1, false);
            }

            // Finally assign the processed data to the output parameter.
            DA.SetDataList(0, RfemMemberList);


            //clears and resets all input parameters.
            // this is done to ensure that if function is repeadedly run, then parameters are re-read and redefined
            rfemLinesInput.Clear();
            sectionIdInput      = "";
            materialIdInput     = "";
            rfemHingeStartInput = new Dlubal.RFEM5.MemberHinge();
            rfemHingeEndInput   = new Dlubal.RFEM5.MemberHinge();
            rotationInput       = 0;
            commentsInput       = "";
        }
        private List <Dlubal.RFEM5.Member> CreateRfemMembers(List <Dlubal.RFEM5.Line> rfemLineMethodIn, string sectionIdMethodIn, string materialIdMethodIn, Dlubal.RFEM5.MemberHinge rfemHingeStartMethodIn, Dlubal.RFEM5.MemberHinge rfemHingeEndMethodIn, double rotationMethodIn, string commentsListMethodIn)
        {
            //---- Interface with RFEM, getting available element numbers ----
            #region Estabilishing connection with RFEM, getting available element numbers

            // Gets interface to running RFEM application.
            IApplication app = Marshal.GetActiveObject("RFEM5.Application") as IApplication;
            // Locks RFEM licence
            app.LockLicense();

            // Gets interface to active RFEM model.
            IModel model = app.GetActiveModel();

            // Gets interface to model data.
            IModelData data = model.GetModelData();

            // Gets Max node, line , line support numbers
            int currentNewMemberNo   = data.GetLastObjectNo(ModelObjectType.MemberObject) + 1;
            int currentNewSectionNo  = data.GetLastObjectNo(ModelObjectType.CrossSectionObject) + 1;
            int currentNewMaterialNo = data.GetLastObjectNo(ModelObjectType.MaterialObject) + 1;
            int currentNewHingeNo    = data.GetLastObjectNo(ModelObjectType.MemberHingeObject) + 1;

            #endregion

            //---- Defining material, cross section and releases ----
            #region Defining material, cross section and releases

            //define material
            Dlubal.RFEM5.Material material = new Dlubal.RFEM5.Material();
            material.No        = currentNewMaterialNo;
            material.TextID    = materialIdMethodIn;
            material.ModelType = MaterialModelType.IsotropicLinearElasticType;


            //define cross section
            CrossSection tempCrossSection = new CrossSection();
            tempCrossSection.No         = currentNewSectionNo;
            tempCrossSection.TextID     = sectionIdMethodIn;
            tempCrossSection.MaterialNo = currentNewMaterialNo;

            //define member hinge numbers
            if (rfemHingeStartInput.No != -1)
            {
                rfemHingeStartInput.No = currentNewHingeNo;
            }
            if (rfemHingeEndInput.No != -1)
            {
                rfemHingeEndMethodIn.No = currentNewHingeNo + 1;
            }
            #endregion


            //---- Process all lines and create members on those ----
            #region Processing all lines, creating RFEM member objects

            for (int i = 0; i < rfemLineMethodIn.Count; i++)
            {
                //test if line exists
                try
                {
                    data.GetLine(rfemLineMethodIn[i].No, ItemAt.AtNo);
                }
                catch
                {
                    continue;
                }

                //assign member properties
                Dlubal.RFEM5.Member tempMember = new Dlubal.RFEM5.Member();
                tempMember.No                  = currentNewMemberNo;
                tempMember.LineNo              = rfemLineMethodIn[i].No;
                tempMember.EndCrossSectionNo   = currentNewSectionNo;
                tempMember.StartCrossSectionNo = currentNewSectionNo;
                tempMember.TaperShape          = TaperShapeType.Linear;
                tempMember.Rotation.Type       = RotationType.Angle;
                tempMember.Rotation.Angle      = rotationMethodIn * (Math.PI / 180);
                if (rfemHingeStartInput.No != -1)
                {
                    tempMember.StartHingeNo = currentNewHingeNo;
                }
                if (rfemHingeEndInput.No != -1)
                {
                    tempMember.EndHingeNo = currentNewHingeNo + 1;
                }
                tempMember.Comment = commentsListMethodIn;

                // if -1 is input as section, member is created as rigid, otherwise it is "standard"
                if (sectionIdInput == "-1")
                {
                    tempMember.Type = MemberType.Rigid;
                }
                else if (sectionIdInput == "0")
                {
                    tempMember.Type = MemberType.NullMember;
                }
                else
                {
                    tempMember.Type = MemberType.Beam;
                }
                RfemMemberList.Add(tempMember);
                currentNewMemberNo++;
            }

            #endregion

            //---- Writing information in RFEM ----
            #region Writing info to RFEM

            try
            {
                // modification - set model in modification mode, new information can be written
                data.PrepareModification();

                //set material, cross section and start&end hinges
                if (sectionIdInput != "-1")
                {
                    data.SetMaterial(material);
                    data.SetCrossSection(tempCrossSection);
                }
                if (rfemHingeStartInput.No != -1)
                {
                    data.SetMemberHinge(rfemHingeStartInput);
                }
                if (rfemHingeEndInput.No != -1)
                {
                    data.SetMemberHinge(rfemHingeEndMethodIn);
                }


                //This version writes members one-by-one because the data.SetNodes() for array appears not to be working
                //data.SetMembers(RfemMembers);
                foreach (Member currentRfemMember in RfemMemberList)
                {
                    data.SetMember(currentRfemMember);
                }


                // finish modification - RFEM regenerates the data
                data.FinishModification();
            }

            catch (Exception ex)
            {
                MessageBox.Show(ex.Message, "Error - Member Write", MessageBoxButtons.OK, MessageBoxIcon.Error);
            }

            #endregion

            //---- Releases interface to RFEM model -----
            #region Releasing interface to RFEM
            model = null;

            // Unlocks licence and releases interface to RFEM application.
            if (app != null)
            {
                app.UnlockLicense();
                app = null;
            }

            // Cleans Garbage Collector and releases all cached COM interfaces.
            System.GC.Collect();
            System.GC.WaitForPendingFinalizers();
            #endregion

            //output 'success' as true and return member list
            writeSuccess = true;
            return(RfemMemberList);
        }