diff --git a/net/FlatBuffers/ByteBuffer.cs b/net/FlatBuffers/ByteBuffer.cs
index 1ea040278..fcdf8a1da 100755
--- a/net/FlatBuffers/ByteBuffer.cs
+++ b/net/FlatBuffers/ByteBuffer.cs
@@ -35,13 +35,18 @@ namespace FlatBuffers
 
         public byte[] Data { get { return _buffer; } }
 
-        public ByteBuffer(byte[] buffer)
+        public ByteBuffer(byte[] buffer) : this(buffer, 0) { }
+
+        public ByteBuffer(byte[] buffer, int pos)
         {
             _buffer = buffer;
-            _pos = 0;
+            _pos = pos;
         }
 
-        public int Position { get { return _pos; } }
+        public int Position {
+            get { return _pos; }
+            set { _pos = value; }
+        }
 
         // Pre-allocated helper arrays for convertion.
         private float[] floathelper = new[] { 0.0f };
@@ -92,7 +97,6 @@ namespace FlatBuffers
                     _buffer[offset + count - 1 - i] = (byte)(data >> i * 8);
                 }
             }
-            _pos = offset;
         }
 
         protected ulong ReadLittleEndian(int offset, int count)
@@ -129,14 +133,12 @@ namespace FlatBuffers
         {
             AssertOffsetAndLength(offset, sizeof(sbyte));
             _buffer[offset] = (byte)value;
-            _pos = offset;
         }
 
         public void PutByte(int offset, byte value)
         {
             AssertOffsetAndLength(offset, sizeof(byte));
             _buffer[offset] = value;
-            _pos = offset;
         }
 
         // this method exists in order to conform with Java ByteBuffer standards
diff --git a/net/FlatBuffers/FlatBufferBuilder.cs b/net/FlatBuffers/FlatBufferBuilder.cs
index 453b6e5cd..4d43d0dcb 100644
--- a/net/FlatBuffers/FlatBufferBuilder.cs
+++ b/net/FlatBuffers/FlatBufferBuilder.cs
@@ -75,8 +75,8 @@ namespace FlatBuffers
 
             Buffer.BlockCopy(oldBuf, 0, newBuf, newBufSize - oldBufSize,
                              oldBufSize);
-
-            _bb = new ByteBuffer(newBuf);
+            _bb = new ByteBuffer(newBuf, newBufSize);
+            System.Diagnostics.Debug.WriteLine(_bb.Position);
         }
 
         // Prepare to write an element of `size` after `additional_bytes`
@@ -359,6 +359,7 @@ namespace FlatBuffers
         {
             Prep(_minAlign, sizeof(int));
             AddOffset(rootTable);
+            _bb.Position = _space;
         }
 
         public ByteBuffer DataBuffer { get { return _bb; } }
@@ -387,7 +388,7 @@ namespace FlatBuffers
              {
                 AddByte((byte)fileIdentifier[i]);
              }
-             AddOffset(rootTable);
+             Finish(rootTable);
         }
 
 
diff --git a/tests/FlatBuffers.Test/FlatBuffersExampleTests.cs b/tests/FlatBuffers.Test/FlatBuffersExampleTests.cs
index 2066bc617..ddeda7a66 100644
--- a/tests/FlatBuffers.Test/FlatBuffersExampleTests.cs
+++ b/tests/FlatBuffers.Test/FlatBuffersExampleTests.cs
@@ -65,7 +65,6 @@ namespace FlatBuffers.Test
             fbb.AddOffset(test1);
             var testArrayOfString = fbb.EndVector();
 
-
             Monster.StartMonster(fbb);
             Monster.AddPos(fbb, Vec3.CreateVec3(fbb, 1.0f, 2.0f, 3.0f, 3.0,
                                                      Color.Green, (short)5, (sbyte)6));
@@ -79,7 +78,7 @@ namespace FlatBuffers.Test
             Monster.AddTestbool(fbb, false);
             var mon = Monster.EndMonster(fbb);
 
-            fbb.Finish(mon);
+            Monster.FinishMonsterBuffer(fbb, mon);
 
             // Dump to output directory so we can inspect later, if needed
             using (var ms = new MemoryStream(fbb.DataBuffer.Data, fbb.DataBuffer.Position, fbb.Offset))
@@ -90,6 +89,32 @@ namespace FlatBuffers.Test
 
             // Now assert the buffer
             TestBuffer(fbb.DataBuffer);
+
+            //Attempt to mutate Monster fields and check whether the buffer has been mutated properly
+            // revert to original values after testing
+            Monster monster = Monster.GetRootAsMonster(fbb.DataBuffer);
+
+            // mana is optional and does not exist in the buffer so the mutation should fail
+            // the mana field should retain its default value
+            Assert.AreEqual(monster.MutateMana((short)10), false);
+            Assert.AreEqual(monster.Mana, (short)150);
+
+            // testType is an existing field and mutating it should succeed
+            Assert.AreEqual(monster.TestType, Any.Monster);
+            Assert.AreEqual(monster.MutateTestType(Any.NONE), true);
+            Assert.AreEqual(monster.TestType, Any.NONE);
+            Assert.AreEqual(monster.MutateTestType(Any.Monster), true);
+            Assert.AreEqual(monster.TestType, Any.Monster);
+
+            // get a struct field and edit one of its fields
+            Vec3 pos = monster.Pos;
+            Assert.AreEqual(pos.X, 1.0f);
+            pos.MutateX(55.0f);
+            Assert.AreEqual(pos.X, 55.0f);
+            pos.MutateX(1.0f);
+            Assert.AreEqual(pos.X, 1.0f);
+
+            TestBuffer(fbb.DataBuffer);
         }
 
         private void TestBuffer(ByteBuffer bb)