Add Keyed Services Support to Dependency Injection

src/libraries/Microsoft.Extensions.DependencyInjection.Abstractions/src/ActivatorUtilities.cs

@@ -476,6 +476,53 @@ private static bool TryCreateParameterMap(ParameterInfo[] constructorParameters,
             return true;
         }
 
+        private static object? GetService(IServiceProvider serviceProvider, ParameterInfo parameterInfo)
+        {
+            // Handle keyed service
+            if (TryGetServiceKey(parameterInfo, out object? key))
+            {
+                if (serviceProvider is IKeyedServiceProvider keyedServiceProvider)
+                {
+                    return keyedServiceProvider.GetKeyedService(parameterInfo.ParameterType, key);
+                }
+                throw new InvalidOperationException(SR.KeyedServicesNotSupported);
+            }
+            // Try non keyed service
+            return serviceProvider.GetService(parameterInfo.ParameterType);
+        }
+
+        private static bool IsService(IServiceProviderIsService serviceProviderIsService, ParameterInfo parameterInfo)
+        {
+            // Handle keyed service
+            if (TryGetServiceKey(parameterInfo, out object? key))
+            {
+                if (serviceProviderIsService is IServiceProviderIsKeyedService serviceProviderIsKeyedService)
+                {
+                    return serviceProviderIsKeyedService.IsKeyedService(parameterInfo.ParameterType, key);
+                }
+                throw new InvalidOperationException(SR.KeyedServicesNotSupported);
+            }
+            // Try non keyed service
+            return serviceProviderIsService.IsService(parameterInfo.ParameterType);
+        }
+
+        private static bool TryGetServiceKey(ParameterInfo parameterInfo, out object? key)
+        {
+            if (parameterInfo.CustomAttributes != null)
+            {
+                foreach (var attribute in parameterInfo.GetCustomAttributes(true))
+                {
+                    if (attribute is FromKeyedServicesAttribute keyed)
+                    {
+                        key = keyed.Key;
+                        return true;
+                    }
+                }
+            }
+            key = null;
+            return false;
+        }
+
         private readonly struct ConstructorMatcher
         {
             private readonly ConstructorInfo _constructor;
@@ -517,7 +564,7 @@ public int Match(object[] givenParameters, IServiceProviderIsService serviceProv
                 for (int i = 0; i < _parameters.Length; i++)
                 {
                     if (_parameterValues[i] == null &&
-                        !serviceProviderIsService.IsService(_parameters[i].ParameterType))
+                        !IsService(serviceProviderIsService, _parameters[i]))
                     {
                         if (ParameterDefaultValue.TryGetDefaultValue(_parameters[i], out object? defaultValue))
                         {
@@ -539,7 +586,7 @@ public object CreateInstance(IServiceProvider provider)
                 {
                     if (_parameterValues[index] == null)
                     {
-                        object? value = provider.GetService(_parameters[index].ParameterType);
+                        object? value = GetService(provider, _parameters[index]);
                         if (value == null)
                         {
                             if (!ParameterDefaultValue.TryGetDefaultValue(_parameters[index], out object? defaultValue))

src/libraries/Microsoft.Extensions.DependencyInjection.Abstractions/src/Extensions/ServiceCollectionDescriptorExtensions.cs

@@ -10,7 +10,7 @@ namespace Microsoft.Extensions.DependencyInjection.Extensions
     /// <summary>
     /// Extension methods for adding and removing services to an <see cref="IServiceCollection" />.
     /// </summary>
-    public static class ServiceCollectionDescriptorExtensions
+    public static partial class ServiceCollectionDescriptorExtensions
     {
         /// <summary>
         /// Adds the specified <paramref name="descriptor"/> to the <paramref name="collection"/>.
@@ -66,7 +66,8 @@ public static void TryAdd(
             int count = collection.Count;
             for (int i = 0; i < count; i++)
             {
-                if (collection[i].ServiceType == descriptor.ServiceType)
+                if (collection[i].ServiceType == descriptor.ServiceType
+                    && collection[i].ServiceKey == descriptor.ServiceKey)
                 {
                     // Already added
                     return;
@@ -411,7 +412,7 @@ public static void TryAddSingleton<TService>(this IServiceCollection collection,
             ThrowHelper.ThrowIfNull(collection);
             ThrowHelper.ThrowIfNull(instance);
 
-            var descriptor = ServiceDescriptor.Singleton(typeof(TService), instance);
+            var descriptor = ServiceDescriptor.Singleton(serviceType: typeof(TService), implementationInstance: instance);
             TryAdd(collection, descriptor);
         }
 
@@ -472,7 +473,8 @@ public static void TryAddEnumerable(
             {
                 ServiceDescriptor service = services[i];
                 if (service.ServiceType == descriptor.ServiceType &&
-                    service.GetImplementationType() == implementationType)
+                    service.GetImplementationType() == implementationType &&
+                    service.ServiceKey == descriptor.ServiceKey)
                 {
                     // Already added
                     return;
@@ -530,7 +532,7 @@ public static IServiceCollection Replace(
             int count = collection.Count;
             for (int i = 0; i < count; i++)
             {
-                if (collection[i].ServiceType == descriptor.ServiceType)
+                if (collection[i].ServiceType == descriptor.ServiceType && collection[i].ServiceKey == descriptor.ServiceKey)
                 {
                     collection.RemoveAt(i);
                     break;
@@ -564,7 +566,7 @@ public static IServiceCollection RemoveAll(this IServiceCollection collection, T
             for (int i = collection.Count - 1; i >= 0; i--)
             {
                 ServiceDescriptor? descriptor = collection[i];
-                if (descriptor.ServiceType == serviceType)
+                if (descriptor.ServiceType == serviceType && descriptor.ServiceKey == null)
                 {
                     collection.RemoveAt(i);
                 }

src/libraries/Microsoft.Extensions.DependencyInjection.Abstractions/src/FromKeyedServicesAttribute.cs

@@ -0,0 +1,15 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System;
+
+namespace Microsoft.Extensions.DependencyInjection
+{
+    [AttributeUsage(AttributeTargets.Parameter)]
+    public class FromKeyedServicesAttribute : Attribute
+    {
+        public FromKeyedServicesAttribute(object key) => Key = key;
+
+        public object Key { get; }
+    }
+}

src/libraries/Microsoft.Extensions.DependencyInjection.Abstractions/src/IKeyedServiceProvider.cs

@@ -0,0 +1,38 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System;
+
+namespace Microsoft.Extensions.DependencyInjection
+{
+    public interface IKeyedServiceProvider : IServiceProvider
+    {
+        /// <summary>
+        /// Gets the service object of the specified type.
+        /// </summary>
+        /// <param name="serviceType">An object that specifies the type of service object to get.</param>
+        /// <param name="serviceKey">An object that specifies the key of service object to get.</param>
+        /// <returns> A service object of type serviceType. -or- null if there is no service object of type serviceType.</returns>
+        object? GetKeyedService(Type serviceType, object? serviceKey);
+
+        /// <summary>
+        /// Gets service of type <paramref name="serviceType"/> from the <see cref="IServiceProvider"/> implementing
+        /// this interface.
+        /// </summary>
+        /// <param name="serviceType">An object that specifies the type of service object to get.</param>
+        /// <param name="serviceKey">The <see cref="ServiceDescriptor.ServiceKey"/> of the service.</param>
+        /// <returns>A service object of type <paramref name="serviceType"/>.
+        /// Throws an exception if the <see cref="IServiceProvider"/> cannot create the object.</returns>
+        object GetRequiredKeyedService(Type serviceType, object? serviceKey);
+    }
+
+    public static class KeyedService
+    {
+        public static object AnyKey { get; } = new AnyKeyObj();
+
+        private sealed class AnyKeyObj
+        {
+            public override string? ToString() => "*";
+        }
+    }
+}

src/libraries/Microsoft.Extensions.DependencyInjection.Abstractions/src/IServiceProviderIsKeyedService.cs

@@ -0,0 +1,18 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System;
+
+namespace Microsoft.Extensions.DependencyInjection
+{
+    public interface IServiceProviderIsKeyedService : IServiceProviderIsService
+    {
+        /// <summary>
+        /// Determines if the specified service type is available from the <see cref="IServiceProvider"/>.
+        /// </summary>
+        /// <param name="serviceType">An object that specifies the type of service object to test.</param>
+        /// <param name="serviceKey">The <see cref="ServiceDescriptor.ServiceKey"/> of the service.</param>
+        /// <returns>true if the specified service is a available, false if it is not.</returns>
+        bool IsKeyedService(Type serviceType, object? serviceKey);
+    }
+}

src/libraries/Microsoft.Extensions.DependencyInjection.Abstractions/src/Resources/Strings.resx

@@ -167,4 +167,13 @@
     <value>Multiple constructors accepting all given argument types have been found in type '{0}'. There should only be one applicable constructor.</value>
     <comment>{0} = instance type</comment>
   </data>
+  <data name="KeyedServicesNotSupported" xml:space="preserve">
+    <value>This service provider doesn't support keyed services.</value>
+  </data>
+  <data name="KeyedDescriptorMisuse" xml:space="preserve">
+    <value>This service descriptor is keyed. Your service provider may not support keyed services.</value>
+  </data>
+  <data name="NonKeyedDescriptorMisuse" xml:space="preserve">
+    <value>This service descriptor is not keyed.</value>
+  </data>
 </root>