Association in mscrm

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using Microsoft.Xrm.Sdk;
using Microsoft.Xrm.Sdk.Client;
using Microsoft.Xrm.Sdk.Messages;
using Microsoft.Xrm.Sdk.Query;

namespace Commissions
{
    public class User_Commissions:IPlugin
    {
        public void Execute(IServiceProvider serviceProvider)
        {
            #region Context
            IPluginExecutionContext context = (IPluginExecutionContext)serviceProvider.GetService(typeof(IPluginExecutionContext));
            IOrganizationServiceFactory serviceFactory = (IOrganizationServiceFactory)serviceProvider.GetService(typeof(IOrganizationServiceFactory));
            IOrganizationService service = serviceFactory.CreateOrganizationService(context.UserId);
            ITracingService Tracing = (ITracingService)serviceProvider.GetService(typeof(ITracingService));
            Tracing.Trace("Depth= " + context.Depth);
            if (context.Depth > 1)
                return;
            #endregion
            Entity CommissionRoleEnt=null;
            Relationship relationship = new Relationship();
            if (!context.InputParameters.Contains("Relationship"))
            {
               
                //throw new Exception("return");
                Tracing.Trace("return");
                return;
            }
            else
            {
            relationship=(Relationship)context.InputParameters["Relationship"];               
                Tracing.Trace("relationship" + relationship);
            }
            //if(context.PrimaryEntityName.ToLower()=="systemuser"&&context.SecondaryEntityName.ToLower()=="apy_commissionroles")
            // User = service.Retrieve(context.PrimaryEntityName,context.PrimaryEntityId,new ColumnSet(true));apy_apy_commissionroles_systemuser
            //throw new Exception("firing1 " + User);
            if (relationship != null && relationship.SchemaName == "apy_apy_commissionroles_systemuser")
            {
                EntityReference CommissionRole = (EntityReference)context.InputParameters["Target"];
                EntityReferenceCollection UseR = (EntityReferenceCollection)context.InputParameters["RelatedEntities"];
                Tracing.Trace("logicalname= " + UseR[0].LogicalName);
                if (UseR[0].LogicalName == "systemuser" && CommissionRole.LogicalName == "apy_commissionroles")
                {
                    //Guid UserId = ef[0].Id;//service.Retrieve(ef[0].LogicalName, ef[0].Id, new ColumnSet(true));
                    CommissionRoleEnt = service.Retrieve(CommissionRole.LogicalName, CommissionRole.Id, new ColumnSet(true));//target Entity
                    Tracing.Trace("CommissionRoleEnt" + CommissionRoleEnt);
                    bool TopLevelRole = CommissionRoleEnt.Contains("apy_toplevelrole") ? CommissionRoleEnt.GetAttributeValue<Boolean>("apy_toplevelrole") : false;
                    //throw new Exception("TopLevelRole " + TopLevelRole);
                    Tracing.Trace("apy_toplevelrole exists");
                    bool ResultRole = false;
                    if (TopLevelRole == true)
                    {
                        EntityCollection coll = GetCommissionRoles(service, UseR[0].Id, CommissionRole.Id,Tracing);
                        Tracing.Trace("Name= " + UseR[0].Name + "Id= " + UseR[0].Id);
                        //throw new Exception("count="+coll.Entities.Count.ToString());
                        if (coll != null && coll.Entities.Count > 0)
                        {
                            ResultRole = true;
                            //foreach (Entity comm in coll.Entities)
                            //{

                            //    ResultRole = comm.Contains("apy_toplevelrole") ? comm.GetAttributeValue<bool>("apy_toplevelrole") : false;
                            //    if (ResultRole == true)
                            //    {
                                    //break;
                            //    }
                            //}
                        }
                    }
                    if (ResultRole == true)
                    {
                        throw new Exception("You may only have one top level commission role");
                    }
                }
            }
        }

        public EntityCollection GetCommissionRoles(IOrganizationService Service, Guid userId, Guid CommissionId,ITracingService Tracing)
        {
            string fetch = @"<fetch version='1.0' output-format='xml-platform' mapping='logical' distinct='true'>" +
  "<entity name='apy_commissionroles'>" +
    "<attribute name='apy_commissionrolesid' />" +
    "<attribute name='apy_name' />" +
    "<filter type='and'>"+
      "<condition attribute='apy_toplevelrole' operator='eq' value='1' />"+
      "<condition attribute='apy_commissionrolesid' operator='ne' uitype='apy_commissionroles' value='" + CommissionId + "' />" +
    "</filter>"+
    "<order attribute='apy_name' descending='false' />" +
    "<link-entity name='apy_apy_commissionroles_systemuser' from='apy_commissionrolesid' to='apy_commissionrolesid' visible='false' intersect='true'>" +
      "<link-entity name='systemuser' from='systemuserid' to='systemuserid' alias='aa'>"+
    "<filter type='and'>" +
          "<condition attribute='systemuserid' operator='eq'  uitype='systemuser' value='" + userId + "' />" +
        "</filter>" +
      "</link-entity>" +
    "</link-entity>" +
  "</entity>" +
"</fetch>";
            EntityCollection collection = Service.RetrieveMultiple(new FetchExpression(fetch));           
            if (collection.Entities.Count > 0)
            {
                return collection;
            }
            return null;
        }
    }
}