How to assign Equipment/Facility to existed resource group.

//********* Create New Equipment/Facility *******************************

        Entity Equipment = new Entity("equipment");

        Equipment["name"]="Test Equipment 1";

        Equipment["timezonecode"]=1;

        Equipment["businessunitid"] = new EntityReference("businessunit", new Guid("BusinessUnitId"));

        Guid EquipmentId = _Service.Create(Equipment);

        //************************** Retrieve the Resource group***************

        Entity ResourceGroup = _Service.Retrieve("constraintbasedgroup", new Guid("ResourceGroupId"), new ColumnSet(true));

        //********************* Get the constrains of Resource group***************

        System.Text.StringBuilder builder = new System.Text.StringBuilder(ResourceGroup["constraints"].ToString());

        //******* Assing the equipment to resouce group ***************

        builder.Replace("</Body>", " || resource[\"Id\"] ==" + EquipmentId.ToString("B") + " </Body>");

        ResourceGroup["constraints"] = builder.ToString();

        //**************************** Update Resource Group***************

        _Service.Update(ResourceGroup);