Question

Good day everybody,

I’m having troubles with the display of a data that does not always exist.

<div class="display-label">client</div>
<div class="display-field">
  @Model.Contact.client.nomCompteClient
</div>

<div class="display-label">civilite</div>
<div class="display-field">
  @Model.Contact.civilite
</div>

In this code, if @Model.Contact.client.nomCompteClient is not set, I get the following error : Object reference not set to an instance of an object.
But, if every other data is empty, there is no problem, there is just nothing that is displayed.
I don’t understand what I’ve done to set “nomCompteClient” mandatory.

here is my controller :

    Function Details(id As Integer) As ActionResult
        Dim contact As contact = db.contact.Single(Function(c) c.idContact = id)
        Dim meetings = (From d In db.meeting
                        Where d.FK_meet_contact = id
                        Select d).ToList()
        Dim opportunites = (From e In db.opportunite
                          From f In db.transmission_opportunite
                          Where f.FK_trans_cont = id And f.FK_trans_opp = e.idOpportunite
                          Select e).ToList()
        Dim interviews = (From g In db.interview
                          Where g.FK_int_contact = id
                          Select g).ToList()


        Dim model = New ContactDetails With {
            .Contact = contact,
            .Meetings = meetings,
            .Interviews = interviews,
            .Opportunites = opportunites
        }

        Return View(model)
    End Function

Here is the model I’ve used

Public Class ContactDetails
    Public Property Contact As contact
    Public Property Meetings As IEnumerable(Of meeting)
    Public Property Interviews As IEnumerable(Of interview)
    Public Property Opportunites As IEnumerable(Of opportunite)
End Class

Sorry if my english sucks, I’m not a native english speaker.

edit :
I’m not allowed to answer, so I’ll edit with the “solution” I found

I finally fixed it like that :

    <div class="display-field">
    @If Model.Contact.FK_contact_client Then
        @Model.Contact.client.nomCompteClient
        End If
    </div>

FK_contact_client is the FK that refers to the client the contact is working for.

Weren’t there any better possibility?

Answer 1

Your question doesn’t really has anything to do with ASP.NET MVC. It’s a basic .NET question about object references. You have designed an object hierarchy with properties and sub-properties. In order to be able to access Model.Contact.client.nomCompteClient you need to initialize first the Contact property, and then the client property.

Here you seem to be fetching the contact from the database:

Dim contact As contact = db.contact.Single(Function(c) c.idContact = id)

Make sure that in the returned object, the client property is initialized otherwise you cannot use it.

For example here:

@Model.Contact.civilite

this displays nothing because the Contact property is not null but the civilite property even if it is null or empty you no longer try to call any method or property on it.