[C#] Add Offsets and WrapForEncodeAndApplyHeader (#777)

* add field offset

* added WrapForEncodeAndApplyHeader method

* undo whitespaces

* fixed long line checkstyle violation

Author: szehetner

sbe-tool/src/main/java/uk/co/real_logic/sbe/generation/csharp/CSharpGenerator.java

@@ -1035,6 +1035,17 @@ private CharSequence generateMessageFlyweightCode(final String className, final
             indent + INDENT + INDENT + "_actingVersion = SchemaVersion;\n" +
             indent + INDENT + INDENT + "Limit = offset + _actingBlockLength;\n" +
             indent + INDENT + "}\n\n" +
+            indent + INDENT + "public void WrapForEncodeAndApplyHeader(DirectBuffer buffer, int offset, " +
+                " MessageHeader headerEncoder)\n" +
+            indent + INDENT + "{\n" +
+            indent + INDENT + INDENT + "headerEncoder.Wrap(buffer, offset, SchemaVersion);\n" +
+            indent + INDENT + INDENT + "headerEncoder.BlockLength = BlockLength;\n" +
+            indent + INDENT + INDENT + "headerEncoder.TemplateId = TemplateId;\n" +
+            indent + INDENT + INDENT + "headerEncoder.SchemaId = SchemaId;\n" +
+            indent + INDENT + INDENT + "headerEncoder.Version = SchemaVersion;\n" +
+            indent + INDENT + INDENT + "\n" +
+            indent + INDENT + INDENT + "WrapForEncode(buffer, offset + MessageHeader.Size);\n" +
+            indent + INDENT + "}\n\n" +
             indent + INDENT + "public void WrapForDecode(DirectBuffer buffer, int offset, " +
                 "int actingBlockLength, int actingVersion)\n" +
             indent + INDENT + "{\n" +
@@ -1122,6 +1133,11 @@ private void generateFieldIdMethod(final StringBuilder sb, final Token token, fi
             token.id()));
 
         generateSinceActingDeprecated(sb, indent, CSharpUtil.formatPropertyName(token.name()), token);
+
+        sb.append(String.format("\n" +
+            indent + "public const int %sOffset = %d;\n",
+            CSharpUtil.formatPropertyName(token.name()),
+            token.offset()));
     }
 
     private void generateFieldMetaAttributeMethod(final StringBuilder sb, final Token token, final String indent)