Question

I am using Visual studio 2010 with c# and SQL Management studio.

I am working on the mailbox feature.

I written a method for if a user click for reply button the content for reply is like this..

private string adjustContentForReply(List<Guid> sender)
    {
        string content = string.Empty;
        messageID = (Guid)Session["messageID"];

        //haal de ontvangers uit de database van het bericht
        List<Guid> receivers = m.bussinesCollection.BussinesMessageReceiver.GetReceivers(messageID);

        //pas de inhoud van het bericht aan met de details van het vorige bericht
        content = "<br /><br />----------------------------------------<br />";
        content += "Ontvangen op: " + m.bussinesCollection.BussinesMessageReceiver.GetMessageReceiver(messageID, boxOwner).DateReceived.ToString() + "<br />";
        content += "Onderwerp: " + m.bussinesCollection.BussinesMessage.GetMessageSubject(messageID) + "<br />";
        content += "Van: " + m.bussinesCollection.BussinesPerson.GetFullName(sender[0]) + "<br />";
        content += "Aan: ";

        //Voeg één of meerdere ontvangers toe aan details
        foreach (Guid rec in receivers)
        {
            content += m.bussinesCollection.BussinesPerson.GetFullName(rec);
            if (receivers.Count() > 1)
                content += "; ";
        }
        content += "<br />";
        content += "----------------------------------------<br /><br />";

        //voeg de inhoud van het vorige bericht aan de content
        content += m.bussinesCollection.BussinesMessage.GetMessageContent(messageID);

        return content;
    }

It is giving me error in line

content += "Ontvangen op: " + m.bussinesCollection.BussinesMessageReceiver.GetMessageReceiver(messageID, boxOwner).DateReceived.ToString() + "<br />";

the erroe is

Object reference not set to an instance of an object.

the GetMessageReceiver() is like this

public MessageReceiver GetMessageReceiver(Guid msgId, Guid personId)
        {
            var message = from msg in Db.MessageReceivers
                          where msg.MessageID.Equals(msgId) && msg.ReceiverID.Equals(personId)
                          select msg;

          return  message.Count().Equals(1) ? message.First() : null;
        }

when I debugged it and taken the messageId and BoxOwnerId and fire a query in Database,it shows two rows for the given combination.

can any one help me?

Hey the problem is solved from there and now i can create a message for reply.
But on clicking on the send button page the same error now thrown there.

Answer 1

You get the error because you’re not checking the return value of GetMessageReceiver(). You either need to make sure that GetMessageReceiver cannot return null, or you need to check the return value before using any functions on it

MessageReceiver receiver = m.bussinesCollection.BussinesMessageReceiver.GetMessageReceiver(messageID, boxOwner);
if (receiver == null)
    // handle error
    return;

content += "Ontvangen op: " + receiver.DateReceived.ToString() + "<br />";