Run DDL Task Failed When I Try To BeginTransaction In It

Just try this:

1.Create a AS Connection Manager in a package, put the RetainSameConnection property into True.

2.Drag a Run DDL Task, and use the Connection in step1.

3.write the DDL query as this:

<Command>
   <BeginTransaction />
</Command>

4.Run the package.

Result: It said a mistake like this:

   Error: the  element  Command at 7 row, 38 column(Namespace urn:schemas-microsoft-com:xml-analysis)  can not be displayed under Envelope/Body/Execute/Command.

Please help me, what's the hell of this?

Thanks.