Implement new API GetEnumValuesAsUnderlyingType

src/coreclr/nativeaot/System.Private.CoreLib/src/System/RuntimeType.cs

@@ -111,6 +111,14 @@ public sealed override Array GetEnumValues()
             return result;
         }
 
+        public sealed override Array GetEnumValuesAsUnderlyingType()
+        {
+            if (!IsActualEnum)
+                throw new ArgumentException(SR.Arg_MustBeEnum, "enumType");
+
+            return (Array)Enum.GetEnumInfo(this).ValuesAsUnderlyingType.Clone();
+        }
+
         internal bool IsActualEnum
             => TryGetEEType(out EETypePtr eeType) && eeType.IsEnum;
     }

src/libraries/System.ComponentModel.TypeConverter/src/System/ComponentModel/EnumConverter.cs

@@ -171,11 +171,12 @@ private static long GetEnumValue(bool isUnderlyingTypeUInt64, Enum enumVal, Cult
                     bool isUnderlyingTypeUInt64 = Enum.GetUnderlyingType(EnumType) == typeof(ulong);
                     List<Enum> flagValues = new List<Enum>();
 
-                    Array objValues = Enum.GetValues(EnumType);
+                    Array objValues = Enum.GetValuesAsUnderlyingType(EnumType);
                     long[] ulValues = new long[objValues.Length];
                     for (int idx = 0; idx < objValues.Length; idx++)
                     {
-                        ulValues[idx] = GetEnumValue(isUnderlyingTypeUInt64, (Enum)objValues.GetValue(idx)!, culture);
+                        ulValues[idx] = isUnderlyingTypeUInt64 ? unchecked((long)Convert.ToUInt64(objValues.GetValue(idx), culture)) :
+                            Convert.ToInt64(objValues.GetValue(idx), culture);
                     }
 
                     long longValue = GetEnumValue(isUnderlyingTypeUInt64, (Enum)value, culture);

src/libraries/System.Private.CoreLib/src/System/Enum.cs

@@ -315,13 +315,22 @@ public static TEnum[] GetValues<TEnum>() where TEnum : struct, Enum =>
             (TEnum[])GetValues(typeof(TEnum));
 #endif
 
-        [RequiresDynamicCode("It might not be possible to create an array of the enum type at runtime. Use the GetValues<TEnum> overload instead.")]
+        [RequiresDynamicCode("It might not be possible to create an array of the enum type at runtime. Use the GetValues<TEnum> overload or the GetValuesAsUnderlyingType method instead.")]
         public static Array GetValues(Type enumType)
         {
             ArgumentNullException.ThrowIfNull(enumType);
             return enumType.GetEnumValues();
         }
 
+        public static Array GetValuesAsUnderlyingType<TEnum>() where TEnum : struct, Enum =>
+            GetValuesAsUnderlyingType(typeof(TEnum));
+
+        public static Array GetValuesAsUnderlyingType(Type enumType)
+        {
+            ArgumentNullException.ThrowIfNull(enumType);
+            return enumType.GetEnumValuesAsUnderlyingType();
+        }
+
         [Intrinsic]
         public bool HasFlag(Enum flag)
         {

src/libraries/System.Private.CoreLib/src/System/Reflection/SignatureType.cs

@@ -99,7 +99,7 @@ public sealed override Type MakeArrayType(int rank)
         public sealed override string GetEnumName(object value) => throw new NotSupportedException(SR.NotSupported_SignatureType);
         public sealed override string[] GetEnumNames() => throw new NotSupportedException(SR.NotSupported_SignatureType);
         public sealed override Type GetEnumUnderlyingType() => throw new NotSupportedException(SR.NotSupported_SignatureType);
-        [RequiresDynamicCode("It might not be possible to create an array of the enum type at runtime. Use Enum.GetValues<TEnum> instead.")]
+        [RequiresDynamicCode("It might not be possible to create an array of the enum type at runtime. Use the GetEnumValues<TEnum> overload or the GetEnumValuesAsUnderlyingType method instead.")]
         public sealed override Array GetEnumValues() => throw new NotSupportedException(SR.NotSupported_SignatureType);
         public sealed override Guid GUID => throw new NotSupportedException(SR.NotSupported_SignatureType);
         protected sealed override TypeCode GetTypeCodeImpl() => throw new NotSupportedException(SR.NotSupported_SignatureType);

src/libraries/System.Private.CoreLib/src/System/RuntimeType.cs

@@ -7,6 +7,8 @@
 using System.Globalization;
 using System.Reflection;
 using System.Runtime.CompilerServices;
+using System.Threading.Tasks;
+using Internal;
 
 namespace System
 {
@@ -118,7 +120,7 @@ public override string[] GetEnumNames()
             return new ReadOnlySpan<string>(ret).ToArray();
         }
 
-        [RequiresDynamicCode("It might not be possible to create an array of the enum type at runtime. Use the GetValues<TEnum> overload instead.")]
+        [RequiresDynamicCode("It might not be possible to create an array of the enum type at runtime. Use the GetEnumValues<TEnum> overload or the GetEnumValuesAsUnderlyingType method instead.")]
         public override Array GetEnumValues()
         {
             if (!IsActualEnum)
@@ -139,6 +141,25 @@ public override Array GetEnumValues()
             return ret;
         }
 
+        public override Array GetEnumValuesAsUnderlyingType()
+        {
+            if (!IsActualEnum)
+                throw new ArgumentException(SR.Arg_MustBeEnum, "enumType");
+
+            // Get all of the values
+            ulong[] values = Enum.InternalGetValues(this);
+
+            Array ret = Array.CreateInstance(Enum.InternalGetUnderlyingType(this), values.Length);
+
+            for (int i = 0; i < values.Length; i++)
+            {
+                object val = Enum.ToObject(this, values[i]);
+                ret.SetValue(val, i);
+            }
+
+            return ret;
+        }
+
         public override Type GetEnumUnderlyingType()
         {
             if (!IsActualEnum)

src/libraries/System.Private.CoreLib/src/System/Type.cs

@@ -515,7 +515,7 @@ public virtual Type GetEnumUnderlyingType()
             return fields[0].FieldType;
         }
 
-        [RequiresDynamicCode("It might not be possible to create an array of the enum type at runtime. Use Enum.GetValues<TEnum> instead.")]
+        [RequiresDynamicCode("It might not be possible to create an array of the enum type at runtime. Use the GetEnumValues<TEnum> overload or the GetEnumValuesAsUnderlyingType method instead.")]
         public virtual Array GetEnumValues()
         {
             if (!IsEnum)
@@ -526,6 +526,19 @@ public virtual Array GetEnumValues()
             throw NotImplemented.ByDesign;
         }
 
+        [UnconditionalSuppressMessage("AotAnalysis", "IL3050:RequiresDynamicCode",
+            Justification = "The runtime overrides this method with AOT compatible implementation")]
+        public virtual Array GetEnumValuesAsUnderlyingType()
+        {
+            if (!IsEnum)
+                throw new ArgumentException(SR.Arg_MustBeEnum, "enumType");
+
+            Array enumValues = GetEnumValues();
+            Array ret = Array.CreateInstance(GetEnumUnderlyingType(), enumValues.Length);
+            Array.Copy(enumValues, ret, enumValues.Length);
+            return ret;
+        }
+
         [RequiresDynamicCode("The code for an array of the specified type might not be available.")]
         public virtual Type MakeArrayType() => throw new NotSupportedException();
         [RequiresDynamicCode("The code for an array of the specified type might not be available.")]

src/libraries/System.Reflection.MetadataLoadContext/src/System/Reflection/TypeLoading/Types/RoType.cs

@@ -288,6 +288,38 @@ public sealed override Type MakeArrayType(int rank)
         private volatile RoType? _lazyUnderlyingEnumType;
         public sealed override Array GetEnumValues() => throw new InvalidOperationException(SR.Arg_InvalidOperation_Reflection);
 
+#if NET7_0_OR_GREATER
+        [UnconditionalSuppressMessage("ReflectionAnalysis", "IL2085:UnrecognizedReflectionPattern",
+            Justification = "Enum Types are not trimmed.")]
+        public override Array GetEnumValuesAsUnderlyingType()
+        {
+            if (!IsEnum)
+                throw new ArgumentException(SR.Arg_MustBeEnum, "enumType");
+
+            FieldInfo[] enumFields = this.GetFields(BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Static);
+            int numValues = enumFields.Length;
+            Array ret = Type.GetTypeCode(GetEnumUnderlyingType()) switch
+            {
+                TypeCode.Byte => new byte[numValues],
+                TypeCode.SByte => new sbyte[numValues],
+                TypeCode.UInt16 => new ushort[numValues],
+                TypeCode.Int16 => new short[numValues],
+                TypeCode.UInt32 => new uint[numValues],
+                TypeCode.Int32 => new int[numValues],
+                TypeCode.UInt64 => new ulong[numValues],
+                TypeCode.Int64 => new long[numValues],
+                _ => throw new NotSupportedException(),
+            };
+
+            for (int i = 0; i < numValues; i++)
+            {
+                ret.SetValue(enumFields[i].GetRawConstantValue(), i);
+            }
+
+            return ret;
+        }
+#endif
+
         // No trust environment to apply these to.
         public sealed override bool IsSecurityCritical => throw new InvalidOperationException(SR.InvalidOperation_IsSecurity);
         public sealed override bool IsSecuritySafeCritical => throw new InvalidOperationException(SR.InvalidOperation_IsSecurity);

src/libraries/System.Reflection.MetadataLoadContext/tests/src/SampleMetadata/SampleMetadata.cs

@@ -84,6 +84,9 @@ public enum EI4 : int { }
     public enum EU8 : ulong { }
     public enum EI8 : long { }
 
+    public enum E_2_I4 : int { min=int.MinValue, zero=0, one=1, max=int.MaxValue}
+    public enum E_2_U4 : uint { min = uint.MinValue, zero = 0, one = 1, max = uint.MaxValue }
+
     public class GenericEnumContainer<T>
     {
         public enum GenericEnum : short { }

src/libraries/System.Reflection.MetadataLoadContext/tests/src/Tests/Type/TypeTests.cs

@@ -365,6 +365,28 @@ public static IEnumerable<object[]> GetEnumUnderlyingTypeData
             }
         }
 
+        [Fact]
+        public static void GetEnumValuesAsUnderlyingType()
+        {
+            var intEnumType = typeof(E_2_I4).Project();
+            int[] expectedIntValues = { int.MinValue, 0, 1, int.MaxValue };
+            Array intArr = intEnumType.GetEnumValuesAsUnderlyingType();
+            for (int i = 0; i < intArr.Length; i++)
+            {
+                Assert.Equal(expectedIntValues[i], intArr.GetValue(i));
+                Assert.Equal(Type.GetTypeCode(expectedIntValues[i].GetType()), Type.GetTypeCode(intArr.GetValue(i).GetType()));
+            }
+
+            var uintEnumType = typeof(E_2_U4).Project();
+            uint[] expectesUIntValues = { uint.MinValue, 0, 1, uint.MaxValue };
+            Array uintArr = uintEnumType.GetEnumValuesAsUnderlyingType();
+            for (int i = 0; i < uintArr.Length; i++)
+            {
+                Assert.Equal(expectesUIntValues[i], uintArr.GetValue(i));
+                Assert.Equal(Type.GetTypeCode(expectesUIntValues[i].GetType()), Type.GetTypeCode(uintArr.GetValue(i).GetType()));
+            }
+        }
+
         [Theory]
         [MemberData(nameof(GetTypeCodeTheoryData))]
         public static void GettypeCode(TypeWrapper tw, TypeCode expectedTypeCode)

src/libraries/System.Reflection/tests/TypeInfoTests.cs

@@ -457,6 +457,24 @@ private static void GetEnumValues(Type enumType, Array expected)
             Assert.Equal(expected, enumType.GetTypeInfo().GetEnumValues());
         }
 
+        [Fact]
+        public static void GetEnumValuesAsUnderlyingType_Int()
+        {
+            GetEnumValuesAsUnderlyingType(typeof(IntEnum), new int[] { 1, 2, 10, 18, 45 });
+        }
+
+        [Fact]
+        public static void GetEnumValuesAsUnderlyingType_UInt()
+        {
+            GetEnumValues(typeof(UIntEnum), new uint[] { 1, 10 });
+        }
+
+        private static void GetEnumValuesAsUnderlyingType(Type enumType, Array expected)
+        {
+            Assert.Equal(expected, enumType.GetTypeInfo().GetEnumValuesAsUnderlyingType());
+        }
+
+
         [Fact]
         public void GetEnumValues_TypeNotEnum_ThrowsArgumentException()
         {

src/libraries/System.Runtime/ref/System.Runtime.cs

@@ -2312,9 +2312,11 @@ protected Enum() { }
         public static string[] GetNames<TEnum>() where TEnum: struct, System.Enum { throw null; }
         public System.TypeCode GetTypeCode() { throw null; }
         public static System.Type GetUnderlyingType(System.Type enumType) { throw null; }
-        [System.Diagnostics.CodeAnalysis.RequiresDynamicCode("It might not be possible to create an array of the enum type at runtime. Use the GetValues<TEnum> overload instead.")]
+        [System.Diagnostics.CodeAnalysis.RequiresDynamicCode("It might not be possible to create an array of the enum type at runtime. Use the GetValues<TEnum> overload or the GetValuesAsUnderlyingType method instead.")]
         public static System.Array GetValues(System.Type enumType) { throw null; }
         public static TEnum[] GetValues<TEnum>() where TEnum : struct, System.Enum { throw null; }
+        public static System.Array GetValuesAsUnderlyingType(System.Type enumType) { throw null; }
+        public static System.Array GetValuesAsUnderlyingType<TEnum>() where TEnum : struct, System.Enum { throw null; }
         public bool HasFlag(System.Enum flag) { throw null; }
         public static bool IsDefined(System.Type enumType, object value) { throw null; }
         public static bool IsDefined<TEnum>(TEnum value) where TEnum : struct, System.Enum { throw null; }
@@ -5860,8 +5862,9 @@ protected Type() { }
         public virtual string? GetEnumName(object value) { throw null; }
         public virtual string[] GetEnumNames() { throw null; }
         public virtual System.Type GetEnumUnderlyingType() { throw null; }
-        [System.Diagnostics.CodeAnalysis.RequiresDynamicCode("It might not be possible to create an array of the enum type at runtime. Use Enum.GetValues<TEnum> instead.")]
+        [System.Diagnostics.CodeAnalysis.RequiresDynamicCode("It might not be possible to create an array of the enum type at runtime. Use the GetEnumValues<TEnum> overload or the GetEnumValuesAsUnderlyingType method instead.")]
         public virtual System.Array GetEnumValues() { throw null; }
+        public virtual System.Array GetEnumValuesAsUnderlyingType() { throw null; }
         [System.Diagnostics.CodeAnalysis.DynamicallyAccessedMembersAttribute(System.Diagnostics.CodeAnalysis.DynamicallyAccessedMemberTypes.PublicEvents)]
         public System.Reflection.EventInfo? GetEvent(string name) { throw null; }
         [System.Diagnostics.CodeAnalysis.DynamicallyAccessedMembersAttribute(System.Diagnostics.CodeAnalysis.DynamicallyAccessedMemberTypes.NonPublicEvents | System.Diagnostics.CodeAnalysis.DynamicallyAccessedMemberTypes.PublicEvents)]

src/libraries/System.Runtime/tests/System/EnumTests.cs

@@ -1589,6 +1589,76 @@ public static void GetValues_NullEnumType_ThrowsArgumentNullException()
             AssertExtensions.Throws<ArgumentNullException>("enumType", () => Enum.GetValues(null));
         }
 
+        [Fact]
+        public void GetValuesAsUnderlyingType_InvokeSByteEnum_ReturnsExpected()
+        {
+            Array expected = new sbyte[] { 1, 2, sbyte.MaxValue, sbyte.MinValue };
+            Assert.Equal(expected, Enum.GetValuesAsUnderlyingType(typeof(SByteEnum)));
+            Assert.Equal(expected, Enum.GetValuesAsUnderlyingType<SByteEnum>());
+        }
+
+        [Fact]
+        public void GetValuesAsUnderlyingType_InvokeByteEnum_ReturnsExpected()
+        {
+            Array expected = new byte[] { byte.MinValue, 1, 2, byte.MaxValue };
+            Assert.Equal(expected, Enum.GetValuesAsUnderlyingType(typeof(ByteEnum)));
+            Assert.Equal(expected, Enum.GetValuesAsUnderlyingType<ByteEnum>());
+        }
+
+        [Fact]
+        public void GetValuesAsUnderlyingType_InvokeInt16Enum_ReturnsExpected()
+        {
+            Array expected = new short[] { 1, 2, short.MaxValue, short.MinValue };
+            Assert.Equal(expected, Enum.GetValuesAsUnderlyingType(typeof(Int16Enum)));
+            Assert.Equal(expected, Enum.GetValuesAsUnderlyingType<Int16Enum>());
+        }
+
+        [Fact]
+        public void GetValuesAsUnderlyingType_InvokeUInt16Enum_ReturnsExpected()
+        {
+            Array expected = new ushort[] { ushort.MinValue, 1, 2, ushort.MaxValue };
+            Assert.Equal(expected, Enum.GetValuesAsUnderlyingType(typeof(UInt16Enum)));
+            Assert.Equal(expected, Enum.GetValuesAsUnderlyingType<UInt16Enum>());
+        }
+
+        [Fact]
+        public void GetValuesAsUnderlyingType_InvokeInt32Enum_ReturnsExpected()
+        {
+            Array expected = new int[] { 1, 2, int.MaxValue, int.MinValue };
+            Assert.Equal(expected, Enum.GetValuesAsUnderlyingType(typeof(Int32Enum)));
+            Assert.Equal(expected, Enum.GetValuesAsUnderlyingType<Int32Enum>());
+        }
+
+        [Fact]
+        public void GetValuesAsUnderlyingType_InvokeUInt32Enum_ReturnsExpected()
+        {
+            Array expected = new uint[] { uint.MinValue, 1, 2, uint.MaxValue };
+            Assert.Equal(expected, Enum.GetValuesAsUnderlyingType(typeof(UInt32Enum)));
+            Assert.Equal(expected, Enum.GetValuesAsUnderlyingType<UInt32Enum>());
+        }
+
+        [Fact]
+        public void GetValuesAsUnderlyingType_InvokeInt64Enum_ReturnsExpected()
+        {
+            Array expected = new long[] { 1, 2, long.MaxValue, long.MinValue };
+            Assert.Equal(expected, Enum.GetValuesAsUnderlyingType(typeof(Int64Enum)));
+            Assert.Equal(expected, Enum.GetValuesAsUnderlyingType<Int64Enum>());
+        }
+
+        [Fact]
+        public void GetValuesAsUnderlyingType_InvokeUInt64Enum_ReturnsExpected()
+        {
+            Array expected = new ulong[] { ulong.MinValue, 1, 2, ulong.MaxValue };
+            Assert.Equal(expected, Enum.GetValuesAsUnderlyingType(typeof(UInt64Enum)));
+            Assert.Equal(expected, Enum.GetValuesAsUnderlyingType<UInt64Enum>());
+        }
+
+        [Fact]
+        public static void GetValuesAsUnderlyingType_NullEnumType_ThrowsArgumentNullException()
+        {
+            AssertExtensions.Throws<ArgumentNullException>("enumType", () => Enum.GetValuesAsUnderlyingType(null));
+        }
+
         [Theory]
         [InlineData(typeof(object))]
         [InlineData(typeof(int))]

src/tests/nativeaot/SmokeTests/Reflection/Reflection.cs

@@ -1434,6 +1434,12 @@ public static void Run()
                     throw new Exception("GetValues");
             }
 
+            Console.WriteLine("Enum.GetEnumValuesAsUnderlyingType");
+            {
+                if (Enum.GetEnumValuesAsUnderlyingType(typeof(Mine)) is not int[])
+                    throw new Exception("GetEnumValuesAsUnderlyingType");
+            }
+
             Console.WriteLine("Pattern in LINQ expressions");
             {
                 Type objType = typeof(object);