Convert unsigned enums to decimal through their underlying type

src/EFCore/Storage/ValueConversion/EnumToNumberConverter.cs

@@ -94,7 +94,7 @@ private static Expression<Func<TEnum, TNumber>> ToNumber()
         return Expression.Lambda<Func<TEnum, TNumber>>(
             Expression.Convert(
                 typeof(TNumber) == typeof(decimal)
-                    ? Expression.Convert(param, typeof(long))
+                    ? Expression.Convert(param, typeof(TEnum).GetEnumUnderlyingType())
                     : param,
                 typeof(TNumber)), param);
     }
@@ -105,7 +105,7 @@ private static Expression<Func<TNumber, TEnum>> ToEnum()
         return Expression.Lambda<Func<TNumber, TEnum>>(
             Expression.Convert(
                 typeof(TNumber) == typeof(decimal)
-                    ? Expression.Convert(param, typeof(long))
+                    ? Expression.Convert(param, typeof(TEnum).GetEnumUnderlyingType())
                     : param,
                 typeof(TEnum)), param);
     }

test/EFCore.Relational.Specification.Tests/JsonTypesRelationalTestBase.cs

@@ -161,53 +161,6 @@ public virtual Task Can_read_write_collection_of_ASCII_string_JSON_values(object
                 { RelationalAnnotationNames.StoreType, storeType }, { CoreAnnotationNames.Unicode, false }
             });
 
-    public override Task Can_read_write_ulong_enum_JSON_values(EnumU64 value, string json)
-    {
-        if (value == EnumU64.Max)
-        {
-            json = """{"Prop":-1}"""; // Because ulong is converted to long on SQL Server
-        }
-
-        return base.Can_read_write_ulong_enum_JSON_values(value, json);
-    }
-
-    public override Task Can_read_write_nullable_ulong_enum_JSON_values(object? value, string json)
-    {
-        if (Equals(value, ulong.MaxValue))
-        {
-            json = """{"Prop":-1}"""; // Because ulong is converted to long on SQL Server
-        }
-
-        return base.Can_read_write_nullable_ulong_enum_JSON_values(value, json);
-    }
-
-    public override Task Can_read_write_collection_of_ulong_enum_JSON_values()
-        => Can_read_and_write_JSON_value<EnumU64CollectionType, List<EnumU64>>(
-            nameof(EnumU64CollectionType.EnumU64),
-            [
-                EnumU64.Min,
-                EnumU64.Max,
-                EnumU64.Default,
-                EnumU64.One,
-                (EnumU64)8
-            ],
-            """{"Prop":[0,-1,0,1,8]}""", // Because ulong is converted to long on SQL Server
-            mappedCollection: true);
-
-    public override Task Can_read_write_collection_of_nullable_ulong_enum_JSON_values()
-        => Can_read_and_write_JSON_value<NullableEnumU64CollectionType, List<EnumU64?>>(
-            nameof(NullableEnumU64CollectionType.EnumU64),
-            [
-                EnumU64.Min,
-                null,
-                EnumU64.Max,
-                EnumU64.Default,
-                EnumU64.One,
-                (EnumU64?)8
-            ],
-            """{"Prop":[0,null,-1,0,1,8]}""", // Because ulong is converted to long on SQL Server
-            mappedCollection: true);
-
     protected override void AssertElementFacets(IElementType element, Dictionary<string, object?>? facets)
     {
         base.AssertElementFacets(element, facets);

test/EFCore.Sqlite.FunctionalTests/JsonTypesSqliteTest.cs

@@ -223,41 +223,6 @@ protected class HalfType
         public Half Half { get; set; }
     }
 
-    public override Task Can_read_write_ulong_enum_JSON_values(EnumU64 value, string json)
-        => Can_read_and_write_JSON_value<EnumU64Type, EnumU64>(nameof(EnumU64Type.EnumU64), value, json);
-
-    public override Task Can_read_write_nullable_ulong_enum_JSON_values(object? value, string json)
-        => Can_read_and_write_JSON_value<NullableEnumU64Type, EnumU64?>(
-            nameof(NullableEnumU64Type.EnumU64),
-            value == null ? default(EnumU64?) : (EnumU64)value, json);
-
-    public override Task Can_read_write_collection_of_ulong_enum_JSON_values()
-        => Can_read_and_write_JSON_value<EnumU64CollectionType, List<EnumU64>>(
-            nameof(EnumU64CollectionType.EnumU64),
-            [
-                EnumU64.Min,
-                EnumU64.Max,
-                EnumU64.Default,
-                EnumU64.One,
-                (EnumU64)8
-            ],
-            """{"Prop":[0,18446744073709551615,0,1,8]}""",
-            mappedCollection: true);
-
-    public override Task Can_read_write_collection_of_nullable_ulong_enum_JSON_values()
-        => Can_read_and_write_JSON_value<NullableEnumU64CollectionType, List<EnumU64?>>(
-            nameof(NullableEnumU64CollectionType.EnumU64),
-            [
-                EnumU64.Min,
-                null,
-                EnumU64.Max,
-                EnumU64.Default,
-                EnumU64.One,
-                (EnumU64?)8
-            ],
-            """{"Prop":[0,null,18446744073709551615,0,1,8]}""",
-            mappedCollection: true);
-
     protected override ITestStoreFactory NonSharedTestStoreFactory
         => SqliteTestStoreFactory.Instance;
 

test/EFCore.Tests/Storage/ValueConversion/EnumToNumberConverterTest.cs

@@ -124,6 +124,31 @@ public void Can_convert_decimals_to_enums()
         Assert.Equal(default, converter(0));
     }
 
+    private static readonly ValueConverter<Planets, decimal> _unsignedEnumToDecimal
+        = new EnumToNumberConverter<Planets, decimal>();
+
+    [Fact]
+    public void Can_convert_unsigned_enums_to_decimals()
+    {
+        var converter = _unsignedEnumToDecimal.ConvertToProviderExpression.Compile();
+
+        Assert.Equal(1m, converter(Planets.Mercury));
+        Assert.Equal(9223372036854775808m, converter(Planets.Venus));
+        Assert.Equal(18446744073709551615m, converter(Planets.Earth));
+        Assert.Equal(0m, converter(default));
+    }
+
+    [Fact]
+    public void Can_convert_decimals_to_unsigned_enums()
+    {
+        var converter = _unsignedEnumToDecimal.ConvertFromProviderExpression.Compile();
+
+        Assert.Equal(Planets.Mercury, converter(1m));
+        Assert.Equal(Planets.Venus, converter(9223372036854775808m));
+        Assert.Equal(Planets.Earth, converter(18446744073709551615m));
+        Assert.Equal(default, converter(0m));
+    }
+
     private static readonly ValueConverter<Beatles, float> _enumToFloat
         = new EnumToNumberConverter<Beatles, float>();
 
@@ -272,4 +297,11 @@ private enum Beatles
         George = 1,
         Ringo = -1
     }
+
+    private enum Planets : ulong
+    {
+        Mercury = 1,
+        Venus = 9223372036854775808,
+        Earth = ulong.MaxValue
+    }
 }