Support Enums as Keys in OData Client

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<>)))
                 {
                     throw c.Error.InvalidOperation(c.Strings.ClientType_KeysMustBeSimpleTypes(key.Name, typeName, key.PropertyType.FullName));
                 }

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

@@ -6,6 +6,7 @@
 
 using Microsoft.OData.Client.Metadata;
 using System;
+using System.Linq;
 using Xunit;
 
 namespace Microsoft.OData.Client.Tests.Metadata
@@ -50,6 +51,81 @@ 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 Nullable Generic Type
+
+            //Act
+            var keyProperties = ClientTypeUtil.GetKeyPropertiesOnType(employee);
+
+            //Assert
+            Assert.Equal(expectedNumberOfKeyProperties, keyProperties.Length);
+        }
+
+        [Fact]
+        public void IFTypeProperty_HasEnumTypeKeyAttribute_GetKeyPropertiesOnType_DoesNotThrowException()
+        {
+            // Arrange
+            Type employee = typeof(Employee);
+
+            //Act
+            var keyProperties = ClientTypeUtil.GetKeyPropertiesOnType(employee);
+            var 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
+            var keyProperties = ClientTypeUtil.GetKeyPropertiesOnType(employee);
+
+            var empNumKey = keyProperties.Single(k => k.Name == "EmpNumber");
+            var 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_GetKeyPropertiesOnType_DoesNotThrowException()
+        {
+            // Arrange
+            Type employee = typeof(Employee);
+
+            //Act
+            var keyProperties = ClientTypeUtil.GetKeyPropertiesOnType(employee);
+            var key = keyProperties.Single(k => k.Name == "NullableId");
+
+            //Assert
+            Assert.True(key.PropertyType.IsGenericType);
+            Assert.True(key.PropertyType == typeof(System.Nullable<int>));
+        }
+
         public class Person
         {
             [System.ComponentModel.DataAnnotations.Key]
@@ -69,5 +145,41 @@ 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 int? NullableId { get; set; }
+
+            public string Name { get; set; }
+
+            public decimal Salary { get; set; }
+
+            [System.ComponentModel.DataAnnotations.Schema.ForeignKey("DeptNumber")]
+            public Department Department { 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; }
+        }
+
     }
 }