Added support for Nullable<T>.HasValue in SqlExpression - it's equivalent to "!= null"

Author: shift-evgeny

src/ServiceStack.OrmLite/Expressions/SqlExpression.cs

@@ -1337,8 +1337,18 @@ protected virtual object VisitMemberAccess(MemberExpression m)
         {
             if (m.Expression != null)
             {
-                if (m.Member.DeclaringType.IsNullableType() && m.Member.Name == nameof(Nullable<bool>.Value))
-                    return Visit(m.Expression);
+                if (m.Member.DeclaringType.IsNullableType())
+                {
+                    if (m.Member.Name == nameof(Nullable<bool>.Value))
+                        return Visit(m.Expression);
+                    if (m.Member.Name == nameof(Nullable<bool>.HasValue))
+                    {
+                        var doesNotEqualNull = Expression.MakeBinary(ExpressionType.NotEqual, m.Expression, Expression.Constant(null));
+                        return Visit(doesNotEqualNull); // Nullable<T>.HasValue is equivalent to "!= null"
+                    }
+
+                    throw new ArgumentException(string.Format("Expression '{0}' accesses unsupported property '{1}' of Nullable<T>", m, m.Member));
+                }
 
                 if (m.Expression.NodeType == ExpressionType.Parameter || m.Expression.NodeType == ExpressionType.Convert)
                     return GetMemberExpression(m);

tests/ServiceStack.OrmLite.Tests/ExpressionVisitorTests.cs

@@ -173,6 +173,18 @@ public void Can_Select_using_int_array_Contains_Value()
             CollectionAssert.AreEquivalent(new[] { 1, 4 }, target.Select(t => t.Id).ToArray());
         }
 
+        [Test]
+        public void Can_Select_using_Nullable_HasValue()
+        {
+            var q = Db.From<TestType>().Where(x => x.NullableIntCol.HasValue); // WHERE NullableIntCol IS NOT NULL
+            var target = Db.Select(q);
+            CollectionAssert.AreEquivalent(new[] { 1, 3, 4 }, target.Select(t => t.Id).ToArray());
+
+            q = Db.From<TestType>().Where(x => !x.NullableIntCol.HasValue); // WHERE NOT (NullableIntCol IS NOT NULL)
+            target = Db.Select(q);
+            CollectionAssert.AreEquivalent(new[] { 2 }, target.Select(t => t.Id).ToArray());
+        }
+
         [Test]
         public void Can_Select_using_Startswith()
         {