Add ConfigurationKeyNameAttribute to binder and updated tests. (#50338)

src/libraries/Microsoft.Extensions.Configuration.Abstractions/ref/Microsoft.Extensions.Configuration.Abstractions.cs

@@ -15,6 +15,12 @@ public static partial class ConfigurationExtensions
         public static string GetConnectionString(this Microsoft.Extensions.Configuration.IConfiguration configuration, string name) { throw null; }
         public static Microsoft.Extensions.Configuration.IConfigurationSection GetRequiredSection(this Microsoft.Extensions.Configuration.IConfiguration configuration, string key) { throw null; }
     }
+    [System.AttributeUsageAttribute(System.AttributeTargets.Property)]
+    public sealed partial class ConfigurationKeyNameAttribute : System.Attribute
+    {
+        public ConfigurationKeyNameAttribute(string name) { }
+        public string Name { get { throw null; } }
+    }
     public static partial class ConfigurationPath
     {
         public static readonly string KeyDelimiter;

src/libraries/Microsoft.Extensions.Configuration.Abstractions/src/ConfigurationKeyNameAttribute.cs

+// 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.Configuration
+{
+    [AttributeUsage(AttributeTargets.Property)]
+    public sealed class ConfigurationKeyNameAttribute : Attribute
+    {
+        public ConfigurationKeyNameAttribute(string name) => Name = name;
+
+        public string Name { get; }
+    }
+}

src/libraries/Microsoft.Extensions.Configuration.Binder/src/ConfigurationBinder.cs

@@ -208,7 +208,7 @@ private static void BindProperty(PropertyInfo property, object instance, IConfig
                 return;
             }
 
-            propertyValue = BindInstance(property.PropertyType, propertyValue, config.GetSection(property.Name), options);
+            propertyValue = GetPropertyValue(property, instance, config, options);
 
             if (propertyValue != null && hasSetter)
             {
@@ -575,5 +575,48 @@ private static IEnumerable<PropertyInfo> GetAllProperties(Type type)
 
             return allProperties;
         }
+
+        private static object GetPropertyValue(PropertyInfo property, object instance, IConfiguration config, BinderOptions options)
+        {
+            string propertyName = GetPropertyName(property);
+            return BindInstance(
+                property.PropertyType,
+                property.GetValue(instance),
+                config.GetSection(propertyName),
+                options);
+        }
+
+        private static string GetPropertyName(MemberInfo property)
+        {
+            if (property == null)
+            {
+                throw new ArgumentNullException(nameof(property));
+            }
+
+            // Check for a custom property name used for configuration key binding
+            foreach (var attributeData in property.GetCustomAttributesData())
+            {
+                if (attributeData.AttributeType != typeof(ConfigurationKeyNameAttribute))
+                {
+                    continue;
+                }
+
+                // Ensure ConfigurationKeyName constructor signature matches expectations
+                if (attributeData.ConstructorArguments.Count != 1)
+                {
+                    break;
+                }
+
+                // Assumes ConfigurationKeyName constructor first arg is the string key name
+                string name = attributeData
+                    .ConstructorArguments[0]
+                    .Value?
+                    .ToString();
+
+                return !string.IsNullOrWhiteSpace(name) ? name : property.Name;
+            }
+
+            return property.Name;
+        }
     }
 }

src/libraries/Microsoft.Extensions.Configuration.Binder/tests/ConfigurationBinderTests.cs

@@ -34,6 +34,9 @@ public ComplexOptions()
             internal string InternalProperty { get; set; }
             protected string ProtectedProperty { get; set; }
 
+            [ConfigurationKeyName("Named_Property")]
+            public string NamedProperty { get; set; }
+
             protected string ProtectedPrivateSet { get; private set; }
 
             private string PrivateReadOnly { get; }
@@ -201,6 +204,22 @@ public void CanBindIConfigurationSectionWithDerivedOptionsSection()
             Assert.Null(options.Section.Value);
         }
 
+        [Fact]
+        public void CanBindConfigurationKeyNameAttributes()
+        {
+            var dic = new Dictionary<string, string>
+            {
+                {"Named_Property", "Yo"},
+            };
+            var configurationBuilder = new ConfigurationBuilder();
+            configurationBuilder.AddInMemoryCollection(dic);
+            var config = configurationBuilder.Build();
+
+            var options = config.Get<ComplexOptions>();
+            
+            Assert.Equal("Yo", options.NamedProperty);
+        }
+
         [Fact]
         public void EmptyStringIsNullable()
         {