Support for value expression when in sub expression

Author: mythz

src/ServiceStack.OrmLite/Expressions/SqlExpression.cs

@@ -1185,6 +1185,8 @@ protected internal virtual object Visit(Expression exp)
                     return VisitNewArray(exp as NewArrayExpression);
                 case ExpressionType.MemberInit:
                     return VisitMemberInit(exp as MemberInitExpression);
+                case ExpressionType.Index:
+                    return VisitIndexExpression(exp as IndexExpression);
                 default:
                     return exp.ToString();
             }
@@ -1483,14 +1485,30 @@ protected virtual object VisitUnary(UnaryExpression u)
                     return GetNotValue(o);
                 case ExpressionType.Convert:
                     if (u.Method != null)
-                    {
                         return CachedExpressionCompiler.Evaluate(u);
-                    }
                     break;
             }
             return Visit(u.Operand);
         }
 
+        protected virtual object VisitIndexExpression(IndexExpression e)
+        {
+            var arg = e.Arguments[0];
+            var constant = arg as ConstantExpression;
+            var oIndex = constant != null
+                ? constant.Value
+                : CachedExpressionCompiler.Evaluate(arg);
+
+            var index = (int)Convert.ChangeType(oIndex, typeof(int));
+            var oCollection = CachedExpressionCompiler.Evaluate(e.Object);
+
+            var list = oCollection as List<object>;
+            if (list != null)
+                return list[index];
+            
+            throw new NotImplementedException("Unknown Expression: " + e);
+        }
+
         private object GetNotValue(object o)
         {
             if (o as PartialSqlString == null)

tests/ServiceStack.OrmLite.Tests/Issues/SqlExpressionNullConstantIssue.cs

@@ -0,0 +1,65 @@
+using System;
+using NUnit.Framework;
+using ServiceStack.DataAnnotations;
+using ServiceStack.Logging;
+using ServiceStack.Text;
+
+namespace ServiceStack.OrmLite.Tests.Issues
+{
+    public class AnyObjectClass
+    {
+        [Alias("_id")]
+        public Guid Id { get; set; }
+
+        [Alias("_identity")]
+        public Guid? Identity { get; set; }
+
+        [Alias("_name")]
+        [StringLength(250)]
+        public string Name { get; set; }
+    }
+
+    public class SqlExpressionNullConstantIssue : OrmLiteTestBase
+    {
+        [Test]
+        public void Can_compare_null_constant_in_subquery()
+        {
+            LogManager.LogFactory = new ConsoleLogFactory();
+
+            using (var db = OpenDbConnection())
+            {
+                db.DropAndCreateTable<AnyObjectClass>();
+
+                var inQ = db.From<AnyObjectClass>()
+                    .Where(y => y.Identity != null)
+                    .Select(y => y.Identity.Value);
+
+                var q = db.From<AnyObjectClass>().Where(x => Sql.In(x.Identity, inQ));
+
+                var results = db.Select(q);
+
+                results.PrintDump();
+            }
+        }
+
+        [Test]
+        public void Can_compare_null_constant_in_subquery_nested_in_SqlExpression()
+        {
+            LogManager.LogFactory = new ConsoleLogFactory();
+
+            using (var db = OpenDbConnection())
+            {
+                db.DropAndCreateTable<AnyObjectClass>();
+
+                var q = db.From<AnyObjectClass>().Where(x => Sql.In(x.Identity, 
+                    db.From<AnyObjectClass>()
+                        .Where(y => y.Identity != null)
+                        .Select(y => y.Identity.Value)));
+
+                var results = db.Select(q);
+
+                results.PrintDump();
+            }
+        }
+    }
+}

tests/ServiceStack.OrmLite.Tests/ServiceStack.OrmLite.Tests.csproj

@@ -131,6 +131,7 @@
     <Compile Include="Issues\BelongsToIssue.cs" />
     <Compile Include="Issues\JoinBoolSqlServerIssue.cs" />
     <Compile Include="Issues\MergingNestedSqlExpressionIssue.cs" />
+    <Compile Include="Issues\SqlExpressionNullConstantIssue.cs" />
     <Compile Include="Legacy\ApiSqliteLegacyTests.cs" />
     <Compile Include="Legacy\ApiSqlServerLegacyTests.cs" />
     <Compile Include="SchemaTests.cs" />