Automatically register a service into standard DI containers with multiple keys

TryAtSoftware.Extensions.DependencyInjection.Standard/Attributes/ServiceConfigurationAttribute.cs

@@ -10,7 +10,7 @@
 public class ServiceConfigurationAttribute : Attribute
 {
     private ServiceLifetime _lifetime;
-    
+
     /// <summary>
     /// Gets a value indicating whether or not a value is set to the <see cref="Lifetime"/> property.
     /// </summary>
@@ -30,6 +30,26 @@ public ServiceLifetime Lifetime
     }
 
 #if NET8_0_OR_GREATER
-    public string? Key { get; set; }
+    private string[] _keys = [];
+
+    public string? Key
+    {
+        get
+        {
+            if (this.Keys.Length != 1) return null;
+            return this.Keys[0];
+        }
+        set
+        {
+            if (string.IsNullOrWhiteSpace(value)) this.Keys = [];
+            else this.Keys = [value];
+        }
+    }
+
+    public string[] Keys
+    {
+        get => this._keys;
+        set => this._keys = value ?? throw new ArgumentNullException(nameof(value));
+    }
 #endif
 }

TryAtSoftware.Extensions.DependencyInjection.Standard/ServiceRegistrar.cs

@@ -63,14 +63,11 @@ private void RegisterService(Type interfaceType, Type implementationType, Servic
     {
         var lifetime = ExtractLifetime(configurationAttributes);
 
-        ServiceDescriptor? serviceDescriptor = null;
 #if NET8_0_OR_GREATER
-        var key = ExtractKey(configurationAttributes);
-        if (!string.IsNullOrWhiteSpace(key)) serviceDescriptor = new ServiceDescriptor(interfaceType, key, implementationType, lifetime);
+        if (this.RegisterKeyedServiceDescriptors(interfaceType, implementationType, lifetime, configurationAttributes)) return;
 #endif
 
-        serviceDescriptor ??= new ServiceDescriptor(interfaceType, implementationType, lifetime);
-        this._services.Add(serviceDescriptor);
+        this.RegisterServiceDescriptor(interfaceType, implementationType, lifetime);
     }
 
     private static ServiceLifetime ExtractLifetime(ServiceConfigurationAttribute[] configurationAttributes)
@@ -85,15 +82,35 @@ private static ServiceLifetime ExtractLifetime(ServiceConfigurationAttribute[] c
     }
 
 #if NET8_0_OR_GREATER
-    private static string? ExtractKey(ServiceConfigurationAttribute[] configurationAttributes)
+    private static string[] ExtractServiceKeys(ServiceConfigurationAttribute[] configurationAttributes)
     {
         for (var i = configurationAttributes.Length - 1; i >= 0; i--)
         {
-            if (!string.IsNullOrWhiteSpace(configurationAttributes[i].Key))
-                return configurationAttributes[i].Key;
+            if (configurationAttributes[i].Keys.Length > 0)
+                return configurationAttributes[i].Keys;
         }
 
-        return null;
+        return [];
+    }
+
+    private bool RegisterKeyedServiceDescriptors(Type interfaceType, Type implementationType, ServiceLifetime lifetime, ServiceConfigurationAttribute[] configurationAttributes)
+    {
+        var serviceKeys = ExtractServiceKeys(configurationAttributes);
+        if (serviceKeys.Length == 0) return false;
+
+        foreach (var key in serviceKeys)
+        {
+            var serviceDescriptor = new ServiceDescriptor(interfaceType, key, implementationType, lifetime);
+            this._services.Add(serviceDescriptor);
+        }
+
+        return true;
     }
 #endif
+
+    private void RegisterServiceDescriptor(Type interfaceType, Type implementationType, ServiceLifetime lifetime)
+    {
+        var serviceDescriptor = new ServiceDescriptor(interfaceType, implementationType, lifetime);
+        this._services.Add(serviceDescriptor);
+    }
 }