Adjust implementation

csharp/src/Google.Protobuf.Test/Collections/RepeatedFieldTest.cs

@@ -898,26 +898,5 @@ namespace Google.Protobuf.Collections
             Assert.AreEqual(2, span[1]);
             Assert.AreEqual(3, span[2]);
         }
-
-        [Test]
-        public void Memory_Empty()
-        {
-            var list = new RepeatedField<int>();
-            var memory = list.Memory;
-
-            Assert.AreEqual(0, memory.Length);
-        }
-
-        [Test]
-        public void Memory_Access()
-        {
-            var list = new RepeatedField<int> { 1, 2, 3 };
-            var memory = list.Memory;
-
-            Assert.AreEqual(3, memory.Length);
-            Assert.AreEqual(1, memory.Span[0]);
-            Assert.AreEqual(2, memory.Span[1]);
-            Assert.AreEqual(3, memory.Span[2]);
-        }
     }
 }

csharp/src/Google.Protobuf/Collections/RepeatedField.cs

@@ -41,20 +41,15 @@ namespace Google.Protobuf.Collections
         /// Provides read-only access to the data of this <see cref="RepeatedField{T}"/>.
         /// No data is copied so this is the most efficient way of accessing.
         /// </summary>
+        /// <remarks>
+        /// Modifying the contents of the <see cref="RepeatedField{T}"/> while using the returned
+        /// <see cref="ReadOnlySpan{T}"/> can lead to undefined behavior.
+        /// </remarks>
         public ReadOnlySpan<T> Span
         {
             get { return array.AsSpan(0, count); }
         }
 
-        /// <summary>
-        /// Provides read-only access to the data of this <see cref="RepeatedField{T}"/>.
-        /// No data is copied so this is the most efficient way of accessing.
-        /// </summary>
-        public ReadOnlyMemory<T> Memory
-        {
-            get { return array.AsMemory(0, count); }
-        }
-
         /// <summary>
         /// Creates a deep clone of this repeated field.
         /// </summary>