How submit InfoPath form to custom Webservice (WCF)

I use Infopath 2010 and SharePoint 2013. In the InfoPath form i have created a Data Connection, that submit result to my custom WCF webservice.

If i select a field or "entire form" with select "Submit as string", everything works fine. 

If i try to send a "entire form" without "Submit as string", i receive a error.

I tried already to change type of variable ("XmlDocument", "XmlElement"), which receives WCF webservice from Infopath, but i am getting errors.

Is it possible to send a "entire form"  without "Submit as string"? If yes, which type of variable should be in the WCF method ? Please help!