Send a friend invitation a list of users and\or email addresses. 

This method can be accessed through the Friends.asmx file located in:

~/Workarea/webservices/WebServiceAPI/Community/Friends.asmx

[SoapHeader("AuthHeader")]
[SoapHeader("RequestInfoHeader")]
[WebMethod(MessageName = "InviteUsers", Description = "Send a friend invitation a list of users and\\or email addresses.")]
public Collection<Invitation> InviteUsers(InvitationSendRequestData invitationData);

<SoapHeader("AuthHeader")>
<SoapHeader("RequestInfoHeader")>
<WebMethod(MessageName = "InviteUsers", Description = "Send a friend invitation a list of users and\\or email addresses.")>
Public Function InviteUsers(invitationData As InvitationSendRequestData) As Collection<Invitation>