Attach extension action "EnableSoapMTOM" cause error?

Hi all,

Although I follow the instruction of this post "https://success.outsystems.com/Documentation/11/Extensibility_and_Integration/SOAP/Consuming_SOAP_Web_Services/Use_Advanced_Extensibility/Example%3A_Use_MTOM"  correctly to intergrate extension action "EnableSoapMTOM" to  "OnBeforeRequestAdvanced" of SOAP consumer but it still cause this error below

This is screen that I attach "EnableSoapMTOM" action to "OnBeforeRequestAdvanced"

When I remove extension action "EnableSoapMTOM" from  "OnBeforeRequestAdvanced", error disappear. So I guess "logic code" of extension action in .Net Visual Studio is reason why this error happen but I don't know how to fix it. I am really appreciate if anyone can help me.


Regards,

Huy Nguyen,