fix for #157

Author: jogibear9988

src/System.Linq.Dynamic.Core/DynamicQueryableExtensions.cs

@@ -11,6 +11,8 @@
 using System.Reflection;
 using JetBrains.Annotations;
 using System.Linq.Dynamic.Core.Parser;
+using System.Text;
+
 #if WINDOWS_APP
 using System;
 using System.Linq;
@@ -28,7 +30,6 @@ public static class DynamicQueryableExtensions
 #if !(WINDOWS_APP45x || SILVERLIGHT)
         private static readonly TraceSource TraceSource = new TraceSource(typeof(DynamicQueryableExtensions).Name);
 #endif
-        private static readonly Func<MethodInfo, bool> PredicateParameterHas2 = mi => mi.GetParameters()[1].ToString().Contains("Func`2");
 
         private static Expression OptimizeExpression(Expression expression)
         {
@@ -1635,7 +1636,16 @@ public static IQueryable Skip([NotNull] this IQueryable source, int count)
         #endregion Skip
 
         #region SkipWhile
-        private static readonly MethodInfo _skipWhilePredicate = GetMethod(nameof(Queryable.SkipWhile), 1, PredicateParameterHas2);
+
+        private static readonly MethodInfo _skipWhilePredicate = GetMethod(nameof(Queryable.SkipWhile), 1, mi =>
+        {
+            return mi.GetParameters().Length == 1 &&
+                   mi.GetParameters()[1].ParameterType.GetTypeInfo().IsGenericType &&
+                   mi.GetParameters()[1].ParameterType.GetGenericTypeDefinition() == typeof(Expression<>) &&
+                   mi.GetParameters()[1].ParameterType.GetGenericArguments()[0].GetTypeInfo().IsGenericType &&
+                   mi.GetParameters()[1].ParameterType.GetGenericArguments()[0].GetGenericTypeDefinition() ==
+                   typeof(Func<,>);
+        });
 
         /// <summary>
         /// Bypasses elements in a sequence as long as a specified condition is true and then returns the remaining elements.
@@ -1704,7 +1714,16 @@ public static IQueryable Take([NotNull] this IQueryable source, int count)
         #endregion Take
 
         #region TakeWhile
-        private static readonly MethodInfo _takeWhilePredicate = GetMethod(nameof(Queryable.TakeWhile), 1, PredicateParameterHas2);
+
+        private static readonly MethodInfo _takeWhilePredicate = GetMethod(nameof(Queryable.TakeWhile), 1, mi =>
+        {
+            return mi.GetParameters().Length == 1 &&
+                   mi.GetParameters()[1].ParameterType.GetTypeInfo().IsGenericType &&
+                   mi.GetParameters()[1].ParameterType.GetGenericTypeDefinition() == typeof(Expression<>) &&
+                   mi.GetParameters()[1].ParameterType.GetGenericArguments()[0].GetTypeInfo().IsGenericType &&
+                   mi.GetParameters()[1].ParameterType.GetGenericArguments()[0].GetGenericTypeDefinition() ==
+                   typeof(Func<,>);
+        });
 
         /// <summary>
         /// Returns elements from a sequence as long as a specified condition is true.
@@ -2016,10 +2035,8 @@ private static MethodInfo GetMethod(string name, int parameterCount = 0, Func<Me
             }
             catch (Exception ex)
             {
-                TraceSource.TraceEvent(TraceEventType.Error, 0, "Method not found:  {0} - {1}", name, ex);
+               throw new Exception("Method not found: " + name, ex);
             }
-
-            return null;
         }
         #endregion Private Helpers
     }