For stackover flow question http://programmers.stackexchange.com/questions/176826/creating-a-predicate-builder-extension-method

Calling code

//Calling code
[NHibernateActionFilter]
public JsonResult ListContact(long id, [DataSourceRequest] DataSourceRequest request)
{

	IQueryable<Contact> contactList;

	if (id > 0)
		contactList = session.Query<Contact>().Where(y => y.ContactEmailList.Any(x => x.EmailList.Id == id && y.Client.Id == UserHelper.Id));
	else
		contactList = session.Query<Contact>().Where(y => y.Client.Id == UserHelper.Id);

	return contactBuilder2.FilterContacts(contactList, request);
}

//Note: when calling this I get Remotion.Linq.Utilities.ArgumentTypeException
Expected a type implementing IEnumerable<T>, but found 'Domain.Model.Entities.Contact'. Parameter name: expression

namespace Cms.Mvc.Helpers.PredicateBuilders
{
	public class ContactBuilder2 : Controller
	{
		public JsonResult FilterContacts(IQueryable<Contact> contactList, DataSourceRequest request)
		{
			var page = request.Page - 1;
			if (page < 0) page = 0;


			if (request.Filters.Any())
			{
				//Single column
				var filter = request.Filters[0] as FilterDescriptor;
				if (filter != null)
				{
					contactList = contactList.FilterContacts(filter);
				}

				//multiple columns
				var f = request.Filters[0] as CompositeFilterDescriptor;
				if (f != null)
				{
					for (int i = 0; i < f.FilterDescriptors.Count; i++)
					{
						var f2 = f.FilterDescriptors[i] as FilterDescriptor;
						if (f2 != null)
						{
							contactList = contactList.FilterContacts(f2);
						}
					}
				}
			}

			var total = contactList.Count();

			if (request.Sorts.Any())
			{
				switch (request.Sorts[0].Member)
				{
					case "Name":
						contactList = request.Sorts[0].SortDirection == ListSortDirection.Ascending
											  ? contactList.OrderBy(w => w.Firstname).ThenBy(w => w.Lastname)
											  : contactList.OrderByDescending(w => w.Firstname).ThenByDescending(w => w.Lastname);
						break;

					case "Company":
						contactList = request.Sorts[0].SortDirection == ListSortDirection.Ascending
											  ? contactList.OrderBy(w => w.Company).ThenBy(w => w.Firstname).ThenBy(w => w.Lastname)
											  : contactList.OrderByDescending(w => w.Company).ThenBy(w => w.Firstname).ThenBy(w => w.Lastname);
						break;

					default:
						contactList = contactList.OrderBy(w => w.Firstname).ThenBy(w => w.Lastname).ThenBy(w => w.Company);
						break;
				}
			}
			else
				contactList = contactList.OrderBy(w => w.Firstname).ThenBy(w => w.Lastname).ThenBy(w => w.Company);

			var list = contactList.Take(request.PageSize).Skip(page * request.PageSize).ToList().ToPagedList(page, request.PageSize, total);

			//var list = contactList.Take(20).Skip(1 * 25).ToList().ToPagedList(1, 25, total);

			var json = new ContactListDto
			{
				Total = total,
				Data = list.Select(item => new JsonContactSearchDto { Id = item.Id, Name = item.Firstname + " " + item.Lastname, Company = item.Company }).ToList()
			};

			return Json(json, JsonRequestBehavior.AllowGet);
		}

	}

	public static class ContactBuilderExtensions
	{

		public static IQueryable<Contact> FilterContacts(this IQueryable<Contact> contactList, FilterDescriptor filter)
		{
			return contactList.Where(contact => 
				contact.GetFilterStrings(filter.Member).Any(s => s.IsAMatch(filter.Operator, filter.Value.ToString())));
		}

		private static bool IsAMatch(this string filterString, FilterOperator filterOperator, string value)
		{
			switch (filterOperator)
			{
				case FilterOperator.StartsWith:
					return filterString.StartsWith(value);
				case FilterOperator.Contains:
					return filterString.Contains(value);
				case FilterOperator.IsEqualTo:
					return filterString == value;
			}

			throw new ArgumentException(string.Format("Invalid Operator: {0}", filterOperator));
		}

		private static IEnumerable<string> GetFilterStrings(this Contact contact, string member)
		{
			switch (member)
			{
				case "Name":
					return new[]
					 {
						  contact.Firstname, 
						  contact.Lastname, 
						  contact.Firstname + " " + contact.Lastname
					 };
				case "Company":
					return new[]
					 {
						  contact.Company
					 };
			}

			throw new ArgumentException(string.Format("Invalid Member: {0}", member));
		}

	}
}

Error file

Expected a type implementing IEnumerable<T>, but found 'Domain.Model.Entities.Contact'. Parameter name: expression

ERRORSHELPABOUT
Remotion.Linq.Utilities.ArgumentTypeException
Expected a type implementing IEnumerable<T>, but found 'Domain.Model.Entities.Contact'. Parameter name: expression

Remotion.Linq.Parsing.ParserException: Cannot parse expression 'contact' as it has an unsupported type. Only query sources (that is, expressions that implement IEnumerable) and query operators can be parsed. ---> Remotion.Linq.Utilities.ArgumentTypeException: Expected a type implementing IEnumerable<T>, but found 'Domain.Model.Entities.Contact'.
Parameter name: expression
   at Remotion.Linq.ReflectionUtility.GetItemTypeOfIEnumerable(Type enumerableType, String argumentName)
   at Remotion.Linq.Parsing.Structure.IntermediateModel.MainSourceExpressionNode..ctor(String associatedIdentifier, Expression expression)
   at Remotion.Linq.Parsing.Structure.ExpressionTreeParser.ParseNonQueryOperatorExpression(Expression expression, String associatedIdentifier)
   --- End of inner exception stack trace ---
   at Remotion.Linq.Parsing.Structure.ExpressionTreeParser.ParseNonQueryOperatorExpression(Expression expression, String associatedIdentifier)
   at Remotion.Linq.Parsing.Structure.ExpressionTreeParser.ParseNode(Expression expression, String associatedIdentifier)
   at Remotion.Linq.Parsing.Structure.ExpressionTreeParser.ParseMethodCallExpression(MethodCallExpression methodCallExpression, String associatedIdentifier)
   at Remotion.Linq.Parsing.Structure.ExpressionTreeParser.ParseNode(Expression expression, String associatedIdentifier)
   at Remotion.Linq.Parsing.Structure.ExpressionTreeParser.ParseMethodCallExpression(MethodCallExpression methodCallExpression, String associatedIdentifier)
   at Remotion.Linq.Parsing.Structure.ExpressionTreeParser.ParseNode(Expression expression, String associatedIdentifier)
   at Remotion.Linq.Parsing.Structure.ExpressionTreeParser.ParseTree(Expression expressionTree)
   at Remotion.Linq.Parsing.Structure.QueryParser.GetParsedQuery(Expression expressionTreeRoot)
   at Remotion.Linq.Parsing.ExpressionTreeVisitors.SubQueryFindingExpressionTreeVisitor.CreateSubQueryNode(MethodCallExpression methodCallExpression)
   at Remotion.Linq.Parsing.ExpressionTreeVisitors.SubQueryFindingExpressionTreeVisitor.VisitExpression(Expression expression)
   at Remotion.Linq.Parsing.ExpressionTreeVisitor.VisitLambdaExpression(LambdaExpression expression)
   at Remotion.Linq.Parsing.ExpressionTreeVisitor.VisitExpression(Expression expression)
   at Remotion.Linq.Parsing.ExpressionTreeVisitors.SubQueryFindingExpressionTreeVisitor.VisitExpression(Expression expression)
   at Remotion.Linq.Parsing.ExpressionTreeVisitors.SubQueryFindingExpressionTreeVisitor.Process(Expression expressionTree, INodeTypeProvider nodeTypeProvider)
   at Remotion.Linq.Parsing.Structure.MethodCallExpressionParser.ProcessArgumentExpression(Expression argumentExpression)
   at Remotion.Linq.Parsing.Structure.MethodCallExpressionParser.<Parse>b__0(Expression expr)
   at System.Linq.Enumerable.WhereSelectEnumerableIterator`2.MoveNext()
   at System.Linq.Buffer`1..ctor(IEnumerable`1 source)
   at System.Linq.Enumerable.ToArray[TSource](IEnumerable`1 source)
   at Remotion.Linq.Parsing.Structure.MethodCallExpressionParser.Parse(String associatedIdentifier, IExpressionNode source, IEnumerable`1 arguments, MethodCallExpression expressionToParse)
   at Remotion.Linq.Parsing.Structure.ExpressionTreeParser.ParseMethodCallExpression(MethodCallExpression methodCallExpression, String associatedIdentifier)
   at Remotion.Linq.Parsing.Structure.ExpressionTreeParser.ParseNode(Expression expression, String associatedIdentifier)
   at Remotion.Linq.Parsing.Structure.ExpressionTreeParser.ParseMethodCallExpression(MethodCallExpression methodCallExpression, String associatedIdentifier)
   at Remotion.Linq.Parsing.Structure.ExpressionTreeParser.ParseNode(Expression expression, String associatedIdentifier)
   at Remotion.Linq.Parsing.Structure.ExpressionTreeParser.ParseTree(Expression expressionTree)
   at Remotion.Linq.Parsing.Structure.QueryParser.GetParsedQuery(Expression expressionTreeRoot)
   at NHibernate.Linq.NhRelinqQueryParser.Parse(Expression expression)
   at NHibernate.Linq.NhLinqExpression.Translate(ISessionFactoryImplementor sessionFactory)
   at NHibernate.Hql.Ast.ANTLR.ASTQueryTranslatorFactory.CreateQueryTranslators(String queryIdentifier, IQueryExpression queryExpression, String collectionRole, Boolean shallow, IDictionary`2 filters, ISessionFactoryImplementor factory)
   at NHibernate.Engine.Query.HQLExpressionQueryPlan.CreateTranslators(String expressionStr, IQueryExpression queryExpression, String collectionRole, Boolean shallow, IDictionary`2 enabledFilters, ISessionFactoryImplementor factory)
   at NHibernate.Engine.Query.HQLExpressionQueryPlan..ctor(String expressionStr, IQueryExpression queryExpression, String collectionRole, Boolean shallow, IDictionary`2 enabledFilters, ISessionFactoryImplementor factory)
   at NHibernate.Engine.Query.HQLExpressionQueryPlan..ctor(String expressionStr, IQueryExpression queryExpression, Boolean shallow, IDictionary`2 enabledFilters, ISessionFactoryImplementor factory)
   at NHibernate.Engine.Query.QueryPlanCache.GetHQLQueryPlan(IQueryExpression queryExpression, Boolean shallow, IDictionary`2 enabledFilters)
   at NHibernate.Impl.AbstractSessionImpl.GetHQLQueryPlan(IQueryExpression queryExpression, Boolean shallow)
   at NHibernate.Impl.AbstractSessionImpl.CreateQuery(IQueryExpression queryExpression)
   at NHibernate.Linq.DefaultQueryProvider.PrepareQuery(Expression expression, IQuery& query, NhLinqExpression& nhQuery)
   at NHibernate.Linq.DefaultQueryProvider.Execute(Expression expression)
   at NHibernate.Linq.DefaultQueryProvider.Execute[TResult](Expression expression)
   at System.Linq.Queryable.Count[TSource](IQueryable`1 source)
   at Cms.Mvc.Helpers.PredicateBuilders.ContactBuilder2.FilterContacts(IQueryable`1 contactList, DataSourceRequest request) in e:\WebSites\PC\PC-mail\Website\CMS.Website\Cms.Mvc\Helpers\PredicateBuilders\ContactBuilder.cs:line 161
   at Cms.Mvc.Controllers.AJaxClientController.ListContact(Int64 id, DataSourceRequest request) in e:\WebSites\PC\PC-mail\Website\CMS.Website\Cms.Mvc\Controllers\AjaxClientController.cs:line 92
   at lambda_method(Closure , ControllerBase , Object[] )
   at System.Web.Mvc.ActionMethodDispatcher.Execute(ControllerBase controller, Object[] parameters)
   at System.Web.Mvc.ReflectedActionDescriptor.Execute(ControllerContext controllerContext, IDictionary`2 parameters)
   at System.Web.Mvc.ControllerActionInvoker.InvokeActionMethod(ControllerContext controllerContext, ActionDescriptor actionDescriptor, IDictionary`2 parameters)
   at System.Web.Mvc.Async.AsyncControllerActionInvoker.<>c__DisplayClass42.<BeginInvokeSynchronousActionMethod>b__41()
   at System.Web.Mvc.Async.AsyncResultWrapper.<>c__DisplayClass8`1.<BeginSynchronous>b__7(IAsyncResult _)
   at System.Web.Mvc.Async.AsyncResultWrapper.WrappedAsyncResult`1.End()
   at System.Web.Mvc.Async.AsyncControllerActionInvoker.EndInvokeActionMethod(IAsyncResult asyncResult)
   at System.Web.Mvc.Async.AsyncControllerActionInvoker.<>c__DisplayClass37.<>c__DisplayClass39.<BeginInvokeActionMethodWithFilters>b__33()
   at System.Web.Mvc.Async.AsyncControllerActionInvoker.<>c__DisplayClass4f.<InvokeActionMethodFilterAsynchronously>b__49()
   at System.Web.Mvc.Async.AsyncControllerActionInvoker.<>c__DisplayClass4f.<InvokeActionMethodFilterAsynchronously>b__49()
   at System.Web.Mvc.Async.AsyncControllerActionInvoker.<>c__DisplayClass37.<BeginInvokeActionMethodWithFilters>b__36(IAsyncResult asyncResult)
   at System.Web.Mvc.Async.AsyncResultWrapper.WrappedAsyncResult`1.End()
   at System.Web.Mvc.Async.AsyncControllerActionInvoker.EndInvokeActionMethodWithFilters(IAsyncResult asyncResult)
   at System.Web.Mvc.Async.AsyncControllerActionInvoker.<>c__DisplayClass25.<>c__DisplayClass2a.<BeginInvokeAction>b__20()
   at System.Web.Mvc.Async.AsyncControllerActionInvoker.<>c__DisplayClass25.<BeginInvokeAction>b__22(IAsyncResult asyncResult)
   at System.Web.Mvc.Async.AsyncResultWrapper.WrappedAsyncResult`1.End()
   at System.Web.Mvc.Async.AsyncControllerActionInvoker.EndInvokeAction(IAsyncResult asyncResult)
   at System.Web.Mvc.Controller.<>c__DisplayClass1d.<BeginExecuteCore>b__18(IAsyncResult asyncResult)
   at System.Web.Mvc.Async.AsyncResultWrapper.<>c__DisplayClass4.<MakeVoidDelegate>b__3(IAsyncResult ar)
   at System.Web.Mvc.Async.AsyncResultWrapper.WrappedAsyncResult`1.End()
   at System.Web.Mvc.Controller.EndExecuteCore(IAsyncResult asyncResult)
   at System.Web.Mvc.Async.AsyncResultWrapper.<>c__DisplayClass4.<MakeVoidDelegate>b__3(IAsyncResult ar)
   at System.Web.Mvc.Async.AsyncResultWrapper.WrappedAsyncResult`1.End()
   at System.Web.Mvc.Controller.EndExecute(IAsyncResult asyncResult)
   at System.Web.Mvc.Controller.System.Web.Mvc.Async.IAsyncController.EndExecute(IAsyncResult asyncResult)
   at System.Web.Mvc.MvcHandler.<>c__DisplayClass8.<BeginProcessRequest>b__3(IAsyncResult asyncResult)
   at System.Web.Mvc.Async.AsyncResultWrapper.<>c__DisplayClass4.<MakeVoidDelegate>b__3(IAsyncResult ar)
   at System.Web.Mvc.Async.AsyncResultWrapper.WrappedAsyncResult`1.End()
   at System.Web.Mvc.MvcHandler.EndProcessRequest(IAsyncResult asyncResult)
   at System.Web.Mvc.MvcHandler.System.Web.IHttpAsyncHandler.EndProcessRequest(IAsyncResult result)
   at System.Web.HttpApplication.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute()
   at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously)