Late binding

Hi!

I have the following code that needs to be translated into C#(no problems) and used with late binding(???)
A reference to gbaapi.exe is added in the project.

      Dim oGBA As Object
      Dim RetValue
      'Creates the GBA object
      Set oGBA = CreateObject("GBAAPI.GBA")

      'Specifies the data location of the chosen client
      RetValue = oGBA.SetClientPath("c:\program files\mamut\data\client\000\001")
      If RetValue = 0 Then
          Response = MsgBox("The path to the client data location is incorrect.", 0, "MAMUT API")
      End If

      'Adds the contact object to the GBA object
      Dim oContact
      Set oContact = oGBA.CreateContactObject()
      If TypeName(oContact) <> "Object" Then
              Response = MsgBox("An error occurred during the creation of the Contact object.", 0, "MAMUT API")
      End If

      'Create a new contact
      RetValue = oContact.CreateNew()
      If RetValue = 0 Then
          Response = MsgBox("An error occurred during creation of new contact.", 0, "MAMUT API")
      End If

      'Make changes to a contact (after it is retrieved/created)
      oContact.ContName = "Mamut Ltd"
      oContact.Street = "90 Long Acre"
      oContact.City = "London"
      oContact.Zipcode = "WC2E 9RZ"
      oContact.Data56 = 1

      'Save a contact
      RetValue = oContact.Save()
      If RetValue = 0 Then
          Response = MsgBox("An error occurred during saving of contact.", 0, "MAMUT API")
      End If


I tried this:
      public class Faktura
      {
            public bool CreateFaktura()
            {
                  gbaapi.gba GBA = new gbaapi.gba();
                  if(GBA.setclientpath(@"\\SERVER\Mamut\Data\Client\000\001").ToString()!="0")
                  {      
                        gbaapi.contactClass oContact = (gbaapi.contactClass)GBA.createcontactobject();
                        int RetValue = oContact.createnew();
                        if(RetValue==0)
                        {
                              oContact.contname = "Mamut Ltd";
                              oContact.street = "90 Long Acre";
                              oContact.city = "London";
                              oContact.zipcode = "WC2E 9RZ";
                              oContact.data56 = 1;

                               oContact.save()
                        
                              return true;
                        }
                        else
                              return false;
                  }
                  else
                        return false;
            }
      }

But I keep getting this:
No overload for method 'createnew' takes '0' arguments

public virtual new System.Object createnew ( System.Int32 lnContid )
Member of gbaapi.contactClass

The manual says nothing about create new needs an argument:
Creates a new contact. All properties of the Contact object are now blank (default from the client), except Contid to which the next available number in the number series is assigned. If the requested customer number is already in use, the next available number will be assigned.      

Returns the value 0 if an error occurs; otherwise returns the value 1.

What am I doing wrong?