You can't. By then it's too late. That device name shown by the receiving device is calculated locally by it. It learnt the device name of the sending device when it first saw the device and stored it then. For instance if the device did a discovery (Inquiry) and found the device, it then asks the device for its name and stores it.
Thus you can't control the name for one OBEX operation. You have to always have your (sending) device use the name you want to appear in the message.
However, a good way to get some specific text you want to appear on screen is to use it as the name of the file you are sending over OBEX. For instance modifying the example from the user's guide:
' The host part of the URI is the device address, e.g. IrDAAddress.ToString(),
' and the file part is the OBEX object name.
Dim uri As New Uri("obex://112233445566/This is a message to send to the user on screen")
Dim req As New ObexWebRequest(uri)
req.ReadFile("Hello World.txt")
Dim rsp As ObexWebResponse = req.GetResponse()
Console.WriteLine("Response Code: {0} (0x{0:X})", rsp.StatusCode)
Set the message in the filename part of the URL.
Alan J. McFarlane
http://www.alanjmcf.me.uk/
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