Fix Binding with IDictionary<,> implementer types

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

@@ -554,9 +554,9 @@ private static bool CanBindToTheseConstructorParameters(ParameterInfo[] construc
         // Binds and potentially overwrites a concrete dictionary.
         // This differs from BindDictionaryInterface because this method doesn't clone
         // the dictionary; it sets and/or overwrites values directly.
-        // When a user specifies a concrete dictionary in their config class, then that
-        // value is used as-us. When a user specifies an interface (instantiated) in their config class,
-        // then it is cloned to a new dictionary, the same way as other collections.
+        // When a user specifies a concrete dictionary or a concrete class implementing IDictionary<,>
+        // in their config class, then that value is used as-is. When a user specifies an interface (instantiated)
+        // in their config class, then it is cloned to a new dictionary, the same way as other collections.
         [RequiresDynamicCode(DynamicCodeWarningMessage)]
         [RequiresUnreferencedCode("Cannot statically analyze what the element type is of the value objects in the dictionary so its members may be trimmed.")]
         private static void BindConcreteDictionary(
@@ -584,10 +584,17 @@ private static void BindConcreteDictionary(
                 return;
             }
 
-            Type genericType = typeof(Dictionary<,>).MakeGenericType(keyType, valueType);
+            MethodInfo tryGetValue = dictionaryType.GetMethod("TryGetValue", BindingFlags.Public | BindingFlags.Instance)!;
+
+            Debug.Assert(dictionary is not null);
+            // dictionary should be of type Dictionary<,> or of type implementing IDictionary<,>
+            PropertyInfo? setter = dictionary.GetType().GetProperty("Item", BindingFlags.Public | BindingFlags.Instance);
+            if (setter is null || !setter.CanWrite)
+            {
+                // Cannot set any item on the dictionary object.
+                return;
+            }
 
-            MethodInfo tryGetValue = dictionaryType.GetMethod("TryGetValue")!;
-            PropertyInfo setter = genericType.GetProperty("Item", DeclaredOnlyLookup)!;
             foreach (IConfigurationSection child in config.GetChildren())
             {
                 try

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

@@ -1067,7 +1067,7 @@ public void CanBindInitializedIEnumerableAndTheOriginalItemsAreNotMutated()
                 {"AlreadyInitializedIEnumerableInterface:1", "val1"},
                 {"AlreadyInitializedIEnumerableInterface:2", "val2"},
                 {"AlreadyInitializedIEnumerableInterface:x", "valx"},
-                
+
                 {"ICollectionNoSetter:0", "val0"},
                 {"ICollectionNoSetter:1", "val1"},
             };
@@ -1602,5 +1602,61 @@ private class OptionsWithInterdependentProperties
             public IEnumerable<int> FilteredConfigValues => ConfigValues.Where(p => p > 10);
             public IEnumerable<int> ConfigValues { get; set; }
         }
+
+        [Fact]
+        public void DifferentDictionaryBindingCasesTest()
+        {
+            var dic = new Dictionary<string, string>() { { "key", "value" } };
+            var config = new ConfigurationBuilder()
+                .AddInMemoryCollection(dic)
+                .Build();
+
+            Assert.Single(config.Get<Dictionary<string, string>>());
+            Assert.Single(config.Get<IDictionary<string, string>>());
+            Assert.Single(config.Get<ExtendedDictionary<string, string>>());
+            Assert.Single(config.Get<ImplementerOfIDictionaryClass<string, string>>());
+        }
+
+        public class ImplementerOfIDictionaryClass<TKey, TValue> : IDictionary<TKey, TValue>
+        {
+            private Dictionary<TKey, TValue> _dict = new();
+
+            public TValue this[TKey key] { get => _dict[key]; set => _dict[key] = value; }
+
+            public ICollection<TKey> Keys => _dict.Keys;
+
+            public ICollection<TValue> Values => _dict.Values;
+
+            public int Count => _dict.Count;
+
+            public bool IsReadOnly => false;
+
+            public void Add(TKey key, TValue value) => _dict.Add(key, value);
+
+            public void Add(KeyValuePair<TKey, TValue> item) => _dict.Add(item.Key, item.Value);
+
+            public void Clear() => _dict.Clear();
+
+            public bool Contains(KeyValuePair<TKey, TValue> item) => _dict.Contains(item);
+
+            public bool ContainsKey(TKey key) => _dict.ContainsKey(key);
+
+            public void CopyTo(KeyValuePair<TKey, TValue>[] array, int arrayIndex) => throw new NotImplementedException();
+
+            public IEnumerator<KeyValuePair<TKey, TValue>> GetEnumerator() => _dict.GetEnumerator();
+
+            public bool Remove(TKey key) => _dict.Remove(key);
+
+            public bool Remove(KeyValuePair<TKey, TValue> item) => _dict.Remove(item.Key);
+
+            public bool TryGetValue(TKey key, out TValue value) => _dict.TryGetValue(key, out value);
+
+            System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator() => _dict.GetEnumerator();
+        }
+
+        public class ExtendedDictionary<TKey, TValue> : Dictionary<TKey, TValue>
+        {
+
+        }
     }
 }