Add Dictionary<TKey,TValue>.TryAdd(TKey, TValue) method

stephentoub · Jun 7, 2015 · b3b0ba4 · b3b0ba4
1 parent 1bb4f3a
commit b3b0ba4
Showing 1 changed file with 17 additions and 8 deletions.
diff --git a/src/mscorlib/src/System/Collections/Generic/Dictionary.cs b/src/mscorlib/src/System/Collections/Generic/Dictionary.cs
@@ -186,7 +186,14 @@ public TValue this[TKey key] {
         }
 
         public void Add(TKey key, TValue value) {
-            Insert(key, value, true);
+            if (!TryAdd(key, value)) {
+                ThrowHelper.ThrowArgumentException(ExceptionResource.Argument_AddingDuplicate);
+            }
+        }
+
+        public bool TryAdd(TKey key, TValue value)
+        {
+            return Insert(key, value, true);
         }
 
         void ICollection<KeyValuePair<TKey, TValue>>.Add(KeyValuePair<TKey, TValue> keyValuePair) {
@@ -313,7 +320,8 @@ private void Initialize(int capacity) {
             freeList = -1;
         }
 
-        private void Insert(TKey key, TValue value, bool add) {
+        // returns false if the key already existed in the collection, or true if it didn't
+        private bool Insert(TKey key, TValue value, bool add) {
 
             if( key == null ) {
                 ThrowHelper.ThrowArgumentNullException(ExceptionArgument.key);
@@ -329,12 +337,12 @@ private void Insert(TKey key, TValue value, bool add) {
 
             for (int i = buckets[targetBucket]; i >= 0; i = entries[i].next) {
                 if (entries[i].hashCode == hashCode && comparer.Equals(entries[i].key, key)) {
-                    if (add) { 
-                        ThrowHelper.ThrowArgumentException(ExceptionResource.Argument_AddingDuplicate);
+                    if (!add)
+                    {
+                        entries[i].value = value;
+                        version++;
                     }
-                    entries[i].value = value;
-                    version++;
-                    return;
+                    return false;
                 } 
 
 #if FEATURE_RANDOMIZED_STRING_HASHING
@@ -386,6 +394,7 @@ private void Insert(TKey key, TValue value, bool add) {
 #endif // FEATURE_CORECLR
 
 #endif
+            return true;
 
         }
 
@@ -422,7 +431,7 @@ public virtual void OnDeserialization(Object sender) {
                     if ( array[i].Key == null) {
                         ThrowHelper.ThrowSerializationException(ExceptionResource.Serialization_NullKey);
                     }
-                    Insert(array[i].Key, array[i].Value, true);
+                    Add(array[i].Key, array[i].Value);
                 }
             }
             else {