My method looks as follows

    ''' <summary>
    ''' Adds the activity.
    ''' </summary>
    ''' <param name="userid">An  that is derived from the <see cref="Domain.User.ID" /></param>
    ''' <param name="activity">The activity integer that is to be derived from the <see cref="ActivityLogService.LogType" />.</param>
    ''' <param name="ip">An IP V4 IP Address.</param>integer
    ''' <remarks></remarks>
    Public Sub AddActivity(ByVal userid As Integer, ByVal activity As Integer, ByVal ip As String) Implements IActivityLogService.AddActivity
        Dim _activity As ActivityLog = New ActivityLog
        _activity.Activity = activity
        _activity.UserID = userid
        _activity.UserIP = ip.IPAddressToNumber
        _activity.ActivityDate = DateTime.UtcNow

        ActivityLogRepository.AddActivity(_activity)
    End Sub

But when I run Sandcastle, my documentation ends up looking like this

userid Type: System..::..Int32

[Missing documentation for "M:myapp.Core.Domain.ActivityLogService.AddActivity(System.Int32,System.Int32,System.String)"]

activity Type: System..::..Int32

[Missing documentation for "M:myapp.Core.Domain.ActivityLogService.AddActivity(System.Int32,System.Int32,System.String)"]

ip Type: System..::..String

[Missing documentation for "M:myapp.Core.Domain.ActivityLogService.AddActivity(System.Int32,System.Int32,System.String)"]

What am I doing wrong?