* Add unit test and fix public methods access.

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

@@ -1267,7 +1267,7 @@ Expression ParseMemberAccess(Type type, Expression instance)
                         throw ParseError(errorPos, Res.NoApplicableMethod, id, GetTypeName(type));
                     case 1:
                         MethodInfo method = (MethodInfo)mb;
-                        if (!IsPredefinedType(method.DeclaringType))
+                        if (!IsPredefinedType(method.DeclaringType) && !(method.IsPublic && IsPredefinedType(method.ReturnType)))
                             throw ParseError(errorPos, Res.MethodsAreInaccessible, GetTypeName(method.DeclaringType));
 
                         if (method.ReturnType == typeof(void))

test/System.Linq.Dynamic.Core.Tests/ExpressionTests.cs

@@ -59,6 +59,17 @@ public void ExpressionTests_SkipAndTake()
             }
         }
 
+        [Fact]
+        public void ExpressionTests_Method()
+        {
+            var samples1 = User.GenerateSampleModels(3).AsQueryable();
+            var samples2 = User.GenerateSampleModels(3).ToArray();
+
+            var result = samples1.Where("TestMethod(@0)", samples2);
+
+            Assert.Equal(samples1.Count(), result.Count());
+        }
+
         [Fact]
         public void ExpressionTests_StringConcatenation()
         {

test/System.Linq.Dynamic.Core.Tests/Helpers/Models/User.cs

@@ -16,6 +16,11 @@ public class User
 
         public List<Role> Roles { get; set; }
 
+        public bool TestMethod(User other)
+        {
+            return true;
+        }
+
         public static IList<User> GenerateSampleModels(int total, bool allowNullableProfiles = false)
         {
             var list = new List<User>();