Question

I have the following Structure within a class:

Public Structure dataStruct
    Public dataPacket As List(Of Byte)

How do I efficiently use this list?

I have been trying things like:

    If rxDataStruct.dataPacket IsNot Nothing Then
        rxDataStruct.dataPacket.Clear()
    Else
        rxDataStruct.dataPacket = New List(Of Byte)
    End If

or

rxDataStruct.dataPacket = New List(Of Byte) From {0}

but each of these still gives me a ‘Object reference not set to an instance of an object.’ error when I try to call:

 rxDataStruct.dataPacket.Add(BytePacket)

Answer 1

You need to initialize the dataPacket member when creating a dataStruct instance.

Dim value As New dataStruct()
value.dataPacket = new List(Of Byte)()

Note this would be much better if you used a Class instead of Structure here. With a Class you can guarantee the dataPacket member is initialized for all instances by using a field initializer.

Public Class dataStruct 
  Public dataPacket As List(Of Byte) = New List(Of Byte)()
  ..
End Class