Prevent DataSourceLoadOptionsParser from System.InvalidOperationExcep…

…tion on parsing binary filter with value null (#620)

net/DevExtreme.AspNet.Data.Tests/DataSourceLoadOptionsParserTests.cs

@@ -59,6 +59,19 @@ public void MustNotParseDates() {
             Assert.IsType<string>(opts.Filter[1]);
         }
 
+        [Fact]
+        public void MustParseNull() {
+            var opts = new SampleLoadOptions();
+
+            DataSourceLoadOptionsParser.Parse(opts, key => {
+                if(key == DataSourceLoadOptionsParser.KEY_FILTER)
+                    return @"[ ""fieldName"", ""="", null ]";
+                return null;
+            });
+
+            Assert.Equal(new[] { "fieldName", "=", null }, opts.Filter.Cast<string>());
+        }
+
         [Fact]
         public void MustParseNumericAsString() {
             var opts = new SampleLoadOptions();

net/DevExtreme.AspNet.Data.Tests/DeserializeTests.cs

@@ -0,0 +1,21 @@
+using System.Collections;
+using System.Text.Json;
+using Xunit;
+
+namespace DevExtreme.AspNet.Data.Tests {
+
+    public class DeserializeTests {
+        static readonly JsonSerializerOptions TESTS_DEFAULT_SERIALIZER_OPTIONS = new JsonSerializerOptions(JsonSerializerDefaults.Web) {
+            Converters = { new ListConverter() }
+        };
+
+        [Theory]
+        [InlineData(@"[""fieldName"",""="",null]")]
+        [InlineData(@"[[""fieldName1"",""="",""""],""and"",[""fieldName2"",""="",null]]")]
+        public void FilterOperandValueCanBeNull(string rawJsonCriteria) {
+            var deserializedList = JsonSerializer.Deserialize<IList>(rawJsonCriteria, TESTS_DEFAULT_SERIALIZER_OPTIONS);
+            Assert.Equal(3, deserializedList.Count);
+        }
+    }
+
+}

net/DevExtreme.AspNet.Data.Tests/DeserializeTestsEx.cs

@@ -0,0 +1,19 @@
+#if NEWTONSOFT_TESTS
+using System.Collections;
+using Newtonsoft.Json;
+using Xunit;
+
+namespace DevExtreme.AspNet.Data.Tests {
+
+    public class DeserializeTestsEx {
+        [Theory]
+        [InlineData(@"[""fieldName"",""="",null]")]
+        [InlineData(@"[[""fieldName1"",""="",""""],""and"",[""fieldName2"",""="",null]]")]
+        public void FilterOperandValueCanBeNull(string rawJsonCriteria) {
+            var deserializedList = JsonConvert.DeserializeObject<IList>(rawJsonCriteria);
+            Assert.Equal(3, deserializedList.Count);
+        }
+    }
+
+}
+#endif

net/DevExtreme.AspNet.Data/Compatibility.cs

@@ -18,6 +18,9 @@ public static IList UnwrapList(IList deserializedList) {
         }
 
         static object UnwrapJsonElement(object deserializeObject) {
+            if(deserializeObject == null)
+                return null;
+
             if(!(deserializeObject is JsonElement jsonElement))
                 throw new InvalidOperationException();