cleaner like this. everyone respects the builder concept with a build method.

PoweredSoft.DynamicLinq/Fluent/Group/GroupBuilder.cs

@@ -2,6 +2,7 @@
 using System.Collections.Generic;
 using System.Text;
 using System.Linq;
+using PoweredSoft.DynamicLinq.Helpers;
 
 namespace PoweredSoft.DynamicLinq.Fluent
 {
@@ -12,6 +13,13 @@ namespace PoweredSoft.DynamicLinq.Fluent
         public bool Empty => !Parts.Any();
         public Type EqualityComparerType { get; set; }
 
+        public IQueryable Query { get; protected set; }
+
+        public GroupBuilder(IQueryable query)
+        {
+            Query = query;
+        }
+
         public GroupBuilder Path(string path, string propertyName = null)
         {
             if (propertyName == null)
@@ -44,5 +52,14 @@ namespace PoweredSoft.DynamicLinq.Fluent
             EqualityComparerType = type;
             return this;
         }
+
+        public virtual IQueryable Build()
+        {
+            if (Empty)
+                throw new Exception("No group specified, please specify at least one group");
+
+            var ret = QueryableHelpers.GroupBy(Query, Query.ElementType, Parts, Type, EqualityComparerType);
+            return ret;
+        }
     }
 }

PoweredSoft.DynamicLinq/Fluent/Select/SelectBuilder.cs

@@ -1,4 +1,5 @@
-using System;
+using PoweredSoft.DynamicLinq.Helpers;
+using System;
 using System.Collections.Generic;
 using System.Linq;
 using System.Text;
@@ -17,6 +18,12 @@ namespace PoweredSoft.DynamicLinq.Fluent
         public List<SelectPart> Parts = new List<SelectPart>();
         public Type DestinationType { get; set; }
         public bool Empty => Parts?.Count == 0;
+        public IQueryable Query { get; protected set; }
+
+        public SelectBuilder(IQueryable query)
+        {
+            Query = query;
+        }
 
         protected void throwIfUsedOrEmpty(string propertyName)
         {
@@ -108,5 +115,14 @@ namespace PoweredSoft.DynamicLinq.Fluent
             });
             return this;
         }
+
+        public virtual IQueryable Build()
+        {
+            if (Empty)
+                throw new Exception("No select specified, please specify at least one select path");
+
+            var partsTuple = Parts.Select(t => (selectType: t.SelectType, propertyName: t.PropertyName, path: t.Path)).ToList();
+            return QueryableHelpers.Select(Query, partsTuple, DestinationType);
+        }
     }
 }