CODEWITHSUNDEEP
vb.netexception
Molloch
Molloch

Reputation: 2381

Null Reference Exception in line checking for Null?

I have a fairly simple piece of code:

Private _PurchaseDelivery as PurchaseDelivery

Protected Overrides Sub InsertItem(ByVal index As Integer, ByVal item As PurchaseDeliveryItem)
    Dim SKUBin As SKUBin
    If _PurchaseDelivery IsNot Nothing AndAlso _PurchaseDelivery.DefaultSKUBinID.HasValue Then
        SKUBin = item.StockOrderUnit.SKU.SKUBins.GetByBinID(_PurchaseDelivery.DefaultSKUBinID.Value)
        item.SKUBin = SKUBin
    End If

    MyBase.InsertItem(index, item)
End Sub

Which is inside a class which overrides a custom list base. The code is occassionaly throwing an unhandled exception, System.NullReferenceException, on this line when used in production:

    If _PurchaseDelivery IsNot Nothing AndAlso _PurchaseDelivery.DefaultSKUBinID.HasValue Then

DeafultSKUBinID is declared as an Integer? (Nullable Int) in the PurchaseDelivery class. I cannot see what might be causing this error, why would this be returning an error?

Upvotes: 0

Views: 513

Answers (3)

Molloch
Molloch

Reputation: 2381

I eventually found the answer to my own problem. The class causing the error was returning the wrong line number in the exception. I have no idea why.

Any exception in this file returns a line number that it 1 less that the code the caused the exception, so the null reference is on the next line. I have no idea why this occurs, I have removed all whitespace in the file and recompiled and will see if that causes the issue to go away.

Thanks to everyone for their help.

Upvotes: 0

KV Prajapati
KV Prajapati

Reputation: 94645

As per code (In OP) snippet PurchaseDelivery in not instantiated (may be it was created somewhere). You may try to change the if statement like:

Protected Overrides Sub InsertItem(ByVal index As Integer, ByVal item As PurchaseDeliveryItem)
    Dim SKUBin As SKUBin
    If IsNothing(_PurchaseDelivery) Then
           Exit Sub
    End If
    If IsNothing(_PurchaseDelivery.DefaultSKUBinID) Then
           Exit Sub
    End If
    If _PurchaseDelivery.DefaultSKUBinID.HasValue Then
        SKUBin = item.StockOrderUnit.SKU.SKUBins.GetByBinID(_PurchaseDelivery.DefaultSKUBinID.Value)
        item.SKUBin = SKUBin
    End If
    MyBase.InsertItem(index, item)
End Sub

Upvotes: 1

UnhandledExcepSean
UnhandledExcepSean

Reputation: 12804

_PurchaseDelivery.DefaultSKUBinID is nothing.

Private _PurchaseDelivery as PurchaseDelivery

Protected Overrides Sub InsertItem(ByVal index As Integer, ByVal item As PurchaseDeliveryItem)
    Dim SKUBin As SKUBin
    If _PurchaseDelivery IsNot Nothing AndAlso _PurchaseDelivery.DefaultSKUBinID isnot nothing andalso _PurchaseDelivery.DefaultSKUBinID.HasValue Then
        SKUBin = item.StockOrderUnit.SKU.SKUBins.GetByBinID(_PurchaseDelivery.DefaultSKUBinID.Value)
        item.SKUBin = SKUBin
    End If

    MyBase.InsertItem(index, item)
End Sub

Upvotes: 1

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