C# performance optimization to Pad/Prep methods

net/FlatBuffers/ByteBuffer.cs

@@ -146,6 +146,13 @@ namespace FlatBuffers
             _buffer[offset] = value;
         }
 
+        public void PutByte(int offset, byte value, int count)
+        {
+            AssertOffsetAndLength(offset, sizeof(byte) * count);
+            for (var i = 0; i < count; ++i)
+                _buffer[offset + i] = value;
+        }
+
         // this method exists in order to conform with Java ByteBuffer standards
         public void Put(int offset, byte value)
         {

net/FlatBuffers/FlatBufferBuilder.cs

@@ -69,10 +69,7 @@ namespace FlatBuffers
 
         public void Pad(int size)
         {
-            for (var i = 0; i < size; i++)
-            {
-                _bb.PutByte(--_space, 0);
-            }
+             _bb.PutByte(_space -= size, 0, size);
         }
 
         // Doubles the size of the ByteBuffer, and copies the old data towards
@@ -116,6 +113,7 @@ namespace FlatBuffers
                 _space += (int)_bb.Length - oldBufSize;
 
             }
+            if (alignSize > 0)
                 Pad(alignSize);
         }