Fixed: WhereBuilder exception when string variable null

src/NzbDrone.Core.Test/Datastore/WhereBuilderFixture.cs

@@ -66,6 +66,23 @@ namespace NzbDrone.Core.Test.Datastore
             _subject.ToString().Should().Be($"(\"Movies\".\"Id\" = \"Movies\".\"Id\")");
         }
 
+        [Test]
+        public void where_string_is_null()
+        {
+            _subject = Where(x => x.ImdbId == null);
+
+            _subject.ToString().Should().Be($"(\"Movies\".\"ImdbId\" IS NULL)");
+        }
+
+        [Test]
+        public void where_string_is_null_value()
+        {
+            string imdb = null;
+            _subject = Where(x => x.ImdbId == imdb);
+
+            _subject.ToString().Should().Be($"(\"Movies\".\"ImdbId\" IS NULL)");
+        }
+
         [Test]
         public void where_column_contains_string()
         {

src/NzbDrone.Core/Datastore/WhereBuilder.cs

@@ -11,15 +11,13 @@ namespace NzbDrone.Core.Datastore
 {
     public class WhereBuilder : ExpressionVisitor
     {
-        private const DbType EnumerableMultiParameter = (DbType)(-1);
+        protected StringBuilder _sb;
 
+        private const DbType EnumerableMultiParameter = (DbType)(-1);
         private readonly string _paramNamePrefix;
+        private readonly bool _requireConcreteValue = false;
         private int _paramCount = 0;
-        private bool _requireConcreteValue = false;
         private bool _gotConcreteValue = false;
-        protected StringBuilder _sb;
-
-        public DynamicParameters Parameters { get; private set; }
 
         public WhereBuilder(Expression filter, bool requireConcreteValue)
         {
@@ -35,6 +33,8 @@ namespace NzbDrone.Core.Datastore
             }
         }
 
+        public DynamicParameters Parameters { get; private set; }
+
         private string AddParameter(object value, DbType? dbType = null)
         {
             _gotConcreteValue = true;
@@ -61,7 +61,7 @@ namespace NzbDrone.Core.Datastore
 
         protected override Expression VisitMethodCall(MethodCallExpression expression)
         {
-            string method = expression.Method.Name;
+            var method = expression.Method.Name;
 
             switch (expression.Method.Name)
             {
@@ -78,7 +78,7 @@ namespace NzbDrone.Core.Datastore
                     break;
 
                 default:
-                    string msg = string.Format("'{0}' expressions are not yet implemented in the where clause expression tree parser.", method);
+                    var msg = string.Format("'{0}' expressions are not yet implemented in the where clause expression tree parser.", method);
                     throw new NotImplementedException(msg);
             }
 
@@ -87,7 +87,7 @@ namespace NzbDrone.Core.Datastore
 
         protected override Expression VisitMemberAccess(MemberExpression expression)
         {
-            string tableName = TableMapping.Mapper.TableNameMapping(expression.Expression.Type);
+            var tableName = expression != null ? TableMapping.Mapper.TableNameMapping(expression.Expression.Type) : null;
 
             if (tableName != null)
             {
@@ -95,27 +95,26 @@ namespace NzbDrone.Core.Datastore
             }
             else
             {
-                object value = GetRightValue(expression);
+                var value = GetRightValue(expression);
-
+
-                // string is IEnumerable<Char> but we don't want to pick up that case
+                if (value != null)
-                var type = value.GetType();
-                var typeInfo = type.GetTypeInfo();
-                bool isEnumerable =
-                    type != typeof(string) && (
-                        typeInfo.ImplementedInterfaces.Any(ti => ti.IsGenericType && ti.GetGenericTypeDefinition() == typeof(IEnumerable<>)) ||
-                        (typeInfo.IsGenericType && typeInfo.GetGenericTypeDefinition() == typeof(IEnumerable<>)));
-
-                string paramName;
-                if (isEnumerable)
                 {
-                    paramName = AddParameter(value, EnumerableMultiParameter);
+                    // string is IEnumerable<Char> but we don't want to pick up that case
+                    var type = value.GetType();
+                    var typeInfo = type.GetTypeInfo();
+                    var isEnumerable =
+                        type != typeof(string) && (
+                            typeInfo.ImplementedInterfaces.Any(ti => ti.IsGenericType && ti.GetGenericTypeDefinition() == typeof(IEnumerable<>)) ||
+                            (typeInfo.IsGenericType && typeInfo.GetGenericTypeDefinition() == typeof(IEnumerable<>)));
+
+                    var paramName = isEnumerable ? AddParameter(value, EnumerableMultiParameter) : AddParameter(value);
+                    _sb.Append(paramName);
                 }
                 else
                 {
-                    paramName = AddParameter(value);
+                    _gotConcreteValue = true;
+                    _sb.Append("NULL");
                 }
-
-                _sb.Append(paramName);
             }
 
             return expression;
@@ -125,51 +124,78 @@ namespace NzbDrone.Core.Datastore
         {
             if (expression.Value != null)
             {
-                string paramName = AddParameter(expression.Value);
+                var paramName = AddParameter(expression.Value);
                 _sb.Append(paramName);
             }
             else
             {
+                _gotConcreteValue = true;
                 _sb.Append("NULL");
             }
 
             return expression;
         }
 
-        private object GetRightValue(Expression rightExpression)
+        private bool TryGetConstantValue(Expression expression, out object result)
         {
-            object rightValue = null;
+            if (expression is ConstantExpression constExp)
+            {
+                result = constExp.Value;
+                return true;
+            }
 
-            var right = rightExpression as ConstantExpression;
+            result = null;
+            return false;
+        }
 
-            // Value is not directly passed in as a constant
+        private bool TryGetPropertyValue(MemberExpression expression, out object result)
-            if (right == null)
+        {
+            if (expression.Expression is MemberExpression nested)
             {
-                var rightMemberExp = rightExpression as MemberExpression;
-                var parentMemberExpression = rightMemberExp.Expression as MemberExpression;
-
                 // Value is passed in as a property on a parent entity
-                if (parentMemberExpression != null)
+                var container = (nested.Expression as ConstantExpression).Value;
-                {
+                var entity = GetFieldValue(container, nested.Member);
-                    var memberInfo = (rightMemberExp.Expression as MemberExpression).Member;
+                result = GetFieldValue(entity, expression.Member);
-                    var container = ((rightMemberExp.Expression as MemberExpression).Expression as ConstantExpression).Value;
+                return true;
-                    var entity = GetFieldValue(container, memberInfo);
-                    rightValue = GetFieldValue(entity, rightMemberExp.Member);
-                }
-                else
-                {
-                    // Value is passed in as a variable
-                    var parent = (rightMemberExp.Expression as ConstantExpression).Value;
-                    rightValue = GetFieldValue(parent, rightMemberExp.Member);
-                }
             }
-            else
+
+            result = null;
+            return false;
+        }
+
+        private bool TryGetVariableValue(MemberExpression expression, out object result)
+        {
+            // Value is passed in as a variable
+            if (expression.Expression is ConstantExpression nested)
+            {
+                result = GetFieldValue(nested.Value, expression.Member);
+                return true;
+            }
+
+            result = null;
+            return false;
+        }
+
+        private object GetRightValue(Expression expression)
+        {
+            if (TryGetConstantValue(expression, out var constValue))
+            {
+                return constValue;
+            }
+
+            var memberExp = expression as MemberExpression;
+
+            if (TryGetPropertyValue(memberExp, out var propValue))
+            {
+                return propValue;
+            }
+
+            if (TryGetVariableValue(memberExp, out var variableValue))
             {
-                // Value is passed in directly as a constant
+                return variableValue;
-                rightValue = right.Value;
             }
 
-            return rightValue;
+            return null;
         }
 
         private object GetFieldValue(object entity, MemberInfo member)
@@ -187,13 +213,29 @@ namespace NzbDrone.Core.Datastore
             throw new ArgumentException(string.Format("WhereBuilder could not get the value for {0}.{1}.", entity.GetType().Name, member.Name));
         }
 
-        private string Decode(BinaryExpression expression)
+        private bool IsNullVariable(Expression expression)
         {
-            bool isRightSideNullConstant = expression.Right.NodeType ==
+            if (expression.NodeType == ExpressionType.Constant &&
-                ExpressionType.Constant &&
+                TryGetConstantValue(expression, out var constResult) &&
-                ((ConstantExpression)expression.Right).Value == null;
+                constResult == null)
+            {
+                return true;
+            }
+
+            if (expression.NodeType == ExpressionType.MemberAccess &&
+                expression is MemberExpression member &&
+                TryGetVariableValue(member, out var variableResult) &&
+                variableResult == null)
+            {
+                return true;
+            }
+
+            return false;
+        }
 
-            if (isRightSideNullConstant)
+        private string Decode(BinaryExpression expression)
+        {
+            if (IsNullVariable(expression.Right))
             {
                 switch (expression.NodeType)
                 {

src/NzbDrone.Core/Movies/MovieRepository.cs

@@ -120,7 +120,7 @@ namespace NzbDrone.Core.Movies
         public Movie FindByImdbId(string imdbid)
         {
             var imdbIdWithPrefix = Parser.Parser.NormalizeImdbId(imdbid);
-            return Query(x => x.ImdbId == imdbIdWithPrefix).FirstOrDefault();
+            return imdbIdWithPrefix == null ? null : Query(x => x.ImdbId == imdbIdWithPrefix).FirstOrDefault();
         }
 
         public Movie FindByTmdbId(int tmdbid)