SqlExpression: Add support for ConditionalExpression

Author: OlegNadymov

src/ServiceStack.OrmLite/Expressions/SqlExpression.cs

@@ -1241,6 +1241,8 @@ protected internal virtual object Visit(Expression exp)
                     return VisitMemberInit(exp as MemberInitExpression);
                 case ExpressionType.Index:
                     return VisitIndexExpression(exp as IndexExpression);
+                case ExpressionType.Conditional:
+                    return VisitConditional(exp as ConditionalExpression);
                 default:
                     return exp.ToString();
             }
@@ -1496,6 +1498,19 @@ protected bool CheckExpressionForTypes(Expression e, ExpressionType[] types)
                         return true;
                 }
 
+                var condExpr = e as ConditionalExpression;
+                if (condExpr != null)
+                {
+                    if (CheckExpressionForTypes(condExpr.Test, types))
+                        return true;
+
+                    if (CheckExpressionForTypes(condExpr.IfTrue, types))
+                        return true;
+
+                    if (CheckExpressionForTypes(condExpr.IfFalse, types))
+                        return true;
+                }
+
                 var memberExpr = e as MemberExpression;
                 e = memberExpr?.Expression;
             }
@@ -1746,6 +1761,32 @@ protected virtual object VisitIndexExpression(IndexExpression e)
             throw new NotImplementedException("Unknown Expression: " + e);
         }
 
+        protected virtual object VisitConditional(ConditionalExpression e)
+        {
+            var test = IsBooleanComparison(e.Test)
+                ? new PartialSqlString($"{VisitMemberAccess((MemberExpression) e.Test)}={GetQuotedTrueValue()}")
+                : Visit(e.Test);
+
+            if (test is bool)
+            {
+                if ((bool) test)
+                {
+                    var ifTrue = Visit(e.IfTrue);
+                    return ifTrue;
+                }
+
+                var ifFalse = Visit(e.IfFalse);
+                return ifFalse;
+            }
+            else
+            {
+                var ifTrue = Visit(e.IfTrue);
+                var ifFalse = Visit(e.IfFalse);
+
+                return new PartialSqlString($"(CASE WHEN {test} THEN {ifTrue} ELSE {ifFalse} END)");
+            }
+        }
+
         private object GetNotValue(object o)
         {
             if (!(o is PartialSqlString))
@@ -1766,6 +1807,10 @@ protected virtual bool IsColumnAccess(MethodCallExpression m)
             if (methCallExp != null)
                 return IsColumnAccess(methCallExp);
 
+            var condExp = m.Object as ConditionalExpression;
+            if (condExp != null)
+                return IsParameterAccess(condExp);
+
             var exp = m.Object as MemberExpression;
             return IsParameterAccess(exp)
                    && IsJoinedTable(exp.Expression.Type);

tests/ServiceStack.OrmLite.Tests/ExpressionVisitorTests.cs

@@ -499,7 +499,57 @@ public void Can_Where_using_constant_filter()
             var q = Db.From<TestType>().Where(filter);//todo: here Where: null is NULL. May be need to change to 1=1 ?
             var target = Db.Select(q);
             Assert.That(target.Count, Is.EqualTo(4));
+        }
+
+        [Test]
+        public void Can_Where_using_Conditional_filter()
+        {
+            System.Linq.Expressions.Expression<Func<TestType, bool>> filter = x => (x.NullableIntCol == null ? 0 : x.NullableIntCol) == 10;
+            var q = Db.From<TestType>().Where(filter);
+            var target = Db.Select(q);
+            Assert.That(target.Count, Is.EqualTo(1));
+        }
+
+        [Test]
+        public void Can_Where_using_Bool_Conditional_filter()
+        {
+            System.Linq.Expressions.Expression<Func<TestType, bool>> filter = x => (x.BoolCol ? x.NullableIntCol : 0) == 10;
+            var q = Db.From<TestType>().Where(filter);
+            var target = Db.Select(q);
+            Assert.That(target.Count, Is.EqualTo(1));
+        }
+
+        [Test]
+        public void Can_Where_using_Method_with_Conditional_filter()
+        {
+            System.Linq.Expressions.Expression<Func<TestType, bool>> filter = x => (x.TextCol == null ? null : x.TextCol).StartsWith("asdf");
+            var q = Db.From<TestType>().Where(filter);
+            var target = Db.Select(q);
+            Assert.That(target.Count, Is.EqualTo(2));
+        }
+
+        [Test]
+        public void Can_Where_using_Constant_Conditional_filter()
+        {
+            var filterConditional = 10;
+            System.Linq.Expressions.Expression<Func<TestType, bool>> filter = x => (filterConditional > 50 ? 123456789 : x.NullableIntCol) == 10;
+            var q = Db.From<TestType>().Where(filter);
+            Assert.That(q.ToSelectStatement(), Does.Not.Contain("123456789"));
+
+            var target = Db.Select(q);
+            Assert.That(target.Count, Is.EqualTo(1));
+        }
 
+        [Test]
+        public void Can_Where_using_Bool_Constant_Conditional_filter()
+        {
+            var filterConditional = true;
+            System.Linq.Expressions.Expression<Func<TestType, bool>> filter = x => (filterConditional ? x.NullableIntCol : 123456789) == 10;
+            var q = Db.From<TestType>().Where(filter);
+            Assert.That(q.ToSelectStatement(), Does.Not.Contain("123456789"));
+
+            var target = Db.Select(q);
+            Assert.That(target.Count, Is.EqualTo(1));
         }
 
         private int MethodReturningInt(int val)