Question: Is there any similar datatype that I can use to save data in C# in the same way it is saved in TBXML Objective C?

Answer: 
**Your method must return an `ActionForward`, not `void`.** That's the contract for an execute method in Struts and you must respect the contract or your code won't work.

It might be possible to return `null` instead of an `ActionForward` object but that's tricky because the request dispatcher will just return. The current content of the response will be sent to the client and you might get a blank page if you are not managing the response yourself.
As said in the documentations, your method must have a return type **"ActionForward"** and not void.  

I don't understand why you don't want to forward your response to any other page.  

If you want to forward your response to another action, you can do this by simply providing action path in forward tag of struts-config.xml, like 

```
<forward name="success" path="/doAction.do">

```