Add support for Enums as Key in OData Client and Allow $filter with integer value in squote and without squote

src/Microsoft.OData.Client/Metadata/ODataTypeInfo.cs

@@ -321,7 +321,9 @@ private PropertyInfo[] GetKeyProperties()
                     throw c.Error.InvalidOperation(c.Strings.ClientType_KeysOnDifferentDeclaredType(typeName));
                 }
 
-                if (!PrimitiveType.IsKnownType(key.PropertyType) && !(key.PropertyType.GetGenericTypeDefinition() == typeof(System.Nullable<>) && key.PropertyType.GetGenericArguments().First().IsEnum()))
+                // Check if the key property's type is a known primitive, an enum, or a nullable generic.
+                // If it doesn't meet any of these conditions, throw an InvalidOperationException.
+                if (!PrimitiveType.IsKnownType(key.PropertyType) && !key.PropertyType.IsEnum() && !(key.PropertyType.IsGenericType() && key.PropertyType.GetGenericTypeDefinition() == typeof(System.Nullable<>) && key.PropertyType.GetGenericArguments().First().IsEnum()))
                 {
                     throw c.Error.InvalidOperation(c.Strings.ClientType_KeysMustBeSimpleTypes(key.Name, typeName, key.PropertyType.FullName));
                 }

src/Microsoft.OData.Core/EdmExtensionMethods.cs

@@ -122,5 +122,47 @@ public static bool HasKey(IEdmNavigationSource currentNavigationSource, IEdmStru
 
             return false;
         }
+
+        /// <summary>
+        /// Parse an enum integral value to enum member.
+        /// </summary>
+        /// <param name="enumType">edm enum type</param>
+        /// <param name="value">input integral value.</param>
+        /// <param name="enumMember">parsed result.</param>
+        /// <returns>true if parse succeeds, false if parse fails.</returns>
+        public static bool TryParse(this IEdmEnumType enumType, long value, out IEdmEnumMember enumMember)
+        {
+            enumMember = null;
+            foreach (IEdmEnumMember member in enumType.Members)
+            {
+                if (member.Value.Value == value)
+                {
+                    enumMember = member;
+                    return true;
+                }
+            }
+
+            return false;
+        }
+
+        /// <summary>
+        /// Checks if the given member name exists in the enum type.
+        /// </summary>
+        /// <param name="enumType">The enum type.</param>
+        /// <param name="memberName">The member name to check.</param>
+        /// <param name="comparison">The comparison type to use for string comparison. Default is Ordinal.</param>
+        /// <returns>True if the member name exists in the enum type; otherwise, false.</returns>
+        public static bool ContainsMember(this IEdmEnumType enumType, string memberName, StringComparison comparison = StringComparison.Ordinal)
+        {
+            foreach (IEdmEnumMember member in enumType.Members)
+            {
+                if (string.Equals(member.Name, memberName, comparison))
+                {
+                    return true;
+                }
+            }
+
+            return false;
+        }
     }
 }

src/Microsoft.OData.Core/UriParser/Binders/MetadataBindingUtils.cs

@@ -58,19 +58,26 @@ internal static SingleValueNode ConvertToTypeIfNeeded(SingleValueNode source, IE
                 }
 
                 ConstantNode constantNode = source as ConstantNode;
-                if (constantNode != null && constantNode.Value != null && source.TypeReference.IsString() && targetTypeReference.IsEnum())
+                // Check if the source node is a constant node, not null, and the source type is either string or integral
+                // and the target type is an enum.
+                if (constantNode != null && constantNode.Value != null && (source.TypeReference.IsString() || source.TypeReference.IsIntegral()) && targetTypeReference.IsEnum())
                 {
                     string memberName = constantNode.Value.ToString();
                     IEdmEnumType enumType = targetTypeReference.Definition as IEdmEnumType;
-                    if (enumType.Members.Any(m => string.Compare(m.Name, memberName, StringComparison.Ordinal) == 0))
+                    if(enumType.ContainsMember(memberName, StringComparison.Ordinal))
                     {
                         string literalText = ODataUriUtils.ConvertToUriLiteral(constantNode.Value, default(ODataVersion));
-                        return new ConstantNode(new ODataEnumValue(constantNode.Value.ToString(), targetTypeReference.Definition.ToString()), literalText, targetTypeReference);
+                        return new ConstantNode(new ODataEnumValue(memberName, enumType.ToString()), literalText, targetTypeReference);
                     }
-                    else
+
+                    // If the member name is an integral value, we should try to convert it to the enum member name and find the enum member with the matching integral value
+                    if (long.TryParse(memberName, out long memberIntegralValue) && enumType.TryParse(memberIntegralValue, out IEdmEnumMember enumMember))
                     {
-                        throw new ODataException(ODataErrorStrings.Binder_IsNotValidEnumConstant(memberName));
+                        string literalText = ODataUriUtils.ConvertToUriLiteral(enumMember.Name, default(ODataVersion));
+                        return new ConstantNode(new ODataEnumValue(enumMember.Name, enumType.ToString()), literalText, targetTypeReference);
                     }
+
+                    throw new ODataException(ODataErrorStrings.Binder_IsNotValidEnumConstant(memberName));
                 }
 
                 if (!TypePromotionUtils.CanConvertTo(source, source.TypeReference, targetTypeReference))

src/Microsoft.OData.Core/UriParser/TypePromotionUtils.cs

@@ -267,14 +267,15 @@ internal static bool PromoteOperandTypes(
                     return true;
                 }
 
-                // Comparing an enum with a string is valid
-                if (left != null && right != null && left.IsEnum() && right.IsString())
+                // Comparing an enum with a string or int is valid
+                if (left != null && right != null && left.IsEnum() && (right.IsString() || right.IsIntegral()))
                 {
                     right = left;
                     return true;
                 }
 
-                if (left != null && right != null && right.IsEnum() && left.IsString())
+                // Comparing an enum with a string or int is valid
+                if (left != null && right != null && right.IsEnum() && (left.IsString() || left.IsIntegral()))
                 {
                     left = right;
                     return true;

test/FunctionalTests/Microsoft.OData.Client.Tests/Metadata/ClientTypeUtilTests.cs

@@ -6,6 +6,8 @@
 
 using Microsoft.OData.Client.Metadata;
 using System;
+using System.Linq;
+using System.Reflection;
 using Xunit;
 
 namespace Microsoft.OData.Client.Tests.Metadata
@@ -50,6 +52,99 @@ public void IFTypeProperty_HasKeyAttributeAndOneProperty_TypeIsEntityAndDoesNotT
             Assert.True(actualResult);
         }
 
+        [Fact]
+        public void IFType_HasMultipleKeyAttributesWhereOneIsEnum_TypeIsEntityAndDoesNotThrowException()
+        {
+            //Arrange
+            Type employee = typeof(Employee);
+
+            //Act
+            bool actualResult = ClientTypeUtil.TypeOrElementTypeIsEntity(employee);
+
+            //Assert
+            Assert.True(actualResult);
+        }
+
+        [Fact]
+        public void IFTypeProperty_HasMultipleKeyAttributes_GetKeyPropertiesOnType_DoesNotThrowException()
+        {
+            //Arrange
+            Type employee = typeof(Employee);
+
+            int expectedNumberOfKeyProperties = 4; // 2 Primitive Known Types, 1 Enum Type, 1 Enum Nullable Generic Type
+
+            //Act
+            PropertyInfo[] keyProperties = ClientTypeUtil.GetKeyPropertiesOnType(employee);
+
+            //Assert
+            Assert.Equal(expectedNumberOfKeyProperties, keyProperties.Length);
+        }
+
+        [Fact]
+        public void IFTypeProperty_HasEnumTypeKeyAttribute_GetKeyPropertiesOnType_DoesNotThrowException()
+        {
+            // Arrange
+            Type employee = typeof(Employee);
+
+            //Act
+            PropertyInfo[] keyProperties = ClientTypeUtil.GetKeyPropertiesOnType(employee);
+            PropertyInfo key = keyProperties.Single(k => k.Name == "EmpType");
+
+            //Assert
+            Assert.True(key.PropertyType.IsEnum());
+            Assert.True(key.PropertyType == typeof(EmployeeType));
+        }
+
+        [Fact]
+        public void IFTypeProperty_HasKnownPrimitiveTypesKeyAttributes_GetKeyPropertiesOnType_DoesNotThrowException()
+        {
+            // Arrange
+            Type employee = typeof(Employee);
+
+            //Act
+            PropertyInfo[] keyProperties = ClientTypeUtil.GetKeyPropertiesOnType(employee);
+
+            PropertyInfo empNumKey = keyProperties.Single(k => k.Name == "EmpNumber");
+            PropertyInfo deptNumKey = keyProperties.Single(k => k.Name == "DeptNumber");
+
+            //Assert
+            Assert.True(PrimitiveType.IsKnownType(empNumKey.PropertyType) && empNumKey.PropertyType == typeof(int));
+            Assert.True(PrimitiveType.IsKnownType(deptNumKey.PropertyType) && deptNumKey.PropertyType == typeof(string));
+        }
+
+        [Fact]
+        public void IFTypeProperty_HasNullableGenericTypeKeyAttribute_OfTypeEnum_GetKeyPropertiesOnType_DoesNotThrowException()
+        {
+            // Arrange
+            Type employee = typeof(Employee);
+
+            //Act
+            PropertyInfo[] keyProperties = ClientTypeUtil.GetKeyPropertiesOnType(employee);
+            PropertyInfo key = keyProperties.Single(k => k.Name == "NullableEmpType");
+
+            //Assert
+            Assert.True(key.PropertyType.IsGenericType);
+            Assert.True(key.PropertyType == typeof(System.Nullable<EmployeeType>));
+        }
+
+        [Fact]
+        public void IFTypeProperty_HasNullableGenericTypeKey_OfTypeStruct_GetKeyPropertiesOnType_ThrowsException()
+        {
+            // Arrange
+            Type employee = typeof(EmployeeWithNullableStruct);
+
+            PropertyInfo empTypeStructKey = employee.GetProperty("EmpTypeStruct");
+
+            InvalidOperationException expectedException = Error.InvalidOperation(Strings.ClientType_KeysMustBeSimpleTypes(empTypeStructKey.Name, employee.ToString(), empTypeStructKey.PropertyType.FullName));
+
+            //Act
+            InvalidOperationException actualException = Assert.Throws<InvalidOperationException>(() => ClientTypeUtil.GetKeyPropertiesOnType(employee));
+
+            //Assert
+            Assert.NotNull(actualException);
+            Assert.Equal(expectedException.Message, actualException.Message);
+        }
+
         public class Person
         {
             [System.ComponentModel.DataAnnotations.Key]
@@ -69,5 +164,55 @@ public class Car
             public int NonStandardId { get; set; }
         }
 
+        public class Employee
+        {
+            [System.ComponentModel.DataAnnotations.Key]
+            public int EmpNumber { get; set; }
+
+            [System.ComponentModel.DataAnnotations.Key]
+            public string DeptNumber { get; set; }
+
+            [System.ComponentModel.DataAnnotations.Key]
+            public EmployeeType EmpType { get; set; }
+
+            [System.ComponentModel.DataAnnotations.Key]
+            public EmployeeType? NullableEmpType { get; set; }
+
+            public string Name { get; set; }
+
+            [System.ComponentModel.DataAnnotations.Schema.ForeignKey("DeptNumber")]
+            public Department Department { get; set; }
+        }
+
+        public class EmployeeWithNullableStruct
+        {
+            [System.ComponentModel.DataAnnotations.Key]
+            public int EmpNumber { get; set; }
+
+            [System.ComponentModel.DataAnnotations.Key]
+            public EmployeeTypeStruct? EmpTypeStruct { get; set; }
+
+            public string Name { get; set; }
+        }
+
+        public enum EmployeeType
+        {
+            None = 1,
+            FullTime = 2,
+            PartTime = 3
+        }
+
+        public class Department
+        {
+            [System.ComponentModel.DataAnnotations.Key]
+            public string DeptId { get; set; }
+            public string Name { get; set; }
+        }
+
+        public struct EmployeeTypeStruct
+        {
+            public int EmpTypeId { get; set; }
+        }
+
     }
 }