Question

I have a small question about my project you could not know, I understand. But perhaps I have a very simple fault in my following function you could see?

<OperationContract()>
Public Function GetBestFahrer() As Autofahrer
    Dim Database As New Model1Container
    Dim Fahrer As Autofahrer = From d In Database.AutofahrerSet Where d.Unfälle = 0 Select d Order By d.Unfälle Ascending
    If Fahrer Is Nothing Then
        Fahrer = Autofahrer.CreateAutofahrer(0, "Testfahrer", DateTime.Now, 0)
        Database.AutofahrerSet.AddObject(Fahrer)
        Database.SaveChanges()
    End If

    Return Fahrer

End Function

Error message on line with “Dim Fahrer As Autofahrer = …”

Unable to cast object of type
‘System.Data.Objects.ObjectQuery`1[SilverlightApplication4.Web.Autofahrer]’
to type
‘SilverlightApplication4.Web.Autofahrer’.

Answer 1

Fahrer is a single object
From d In Database.AutofahrerSet Where d.Unfälle = 0 Select d Order By d.Unfälle Ascending does not give you a single object

It looks like you want to see if something exists and then create it if it doesn’t.

Try something like this

Dim myCount as integer = (From d In Database.AutofahrerSet Where d.Unfälle = 0 Select d).Count()
if myCount = 0 then
    Fahrer = Autofahrer.CreateAutofahrer(0, "Testfahrer", DateTime.Now, 0)
    Database.AutofahrerSet.AddObject(Fahrer)
    Database.SaveChanges()
else
    Fahrer = (From d In Database.AutofahrerSet Where d.Unfälle = 0 Select d Order By d.Unfälle Ascending).First()
End If