How to check dictionary is null in VB.NET?

Question

Am new to vb.net and doing a work flow in vb.net, i need to check whether a dictionary is null. I have declared a dictionary, but have not assigned any value to it.

When i use IsNothing() method it gives object reference exception. How can i check?

Dim CustDicAs New Dictionary(Of String, Integer)
CustDic.IsNothing()

show the code where it goes wrong – Ric Nov 11 '13 at 09:47 — Ric, Nov 11 '13 at 09:47
http://stackoverflow.com/q/5791/11683 – GSerg Nov 11 '13 at 09:52 — GSerg, Nov 11 '13 at 09:52

Tim Schmelter · Accepted Answer · 2014-12-23T20:33:02.507

5

You check variables for Nothing with Not Is Nothing or IsNot Nothing or via the old IsNothing function from Visual Basic.

Dim dict As Dictionary(Of String, String)

Not Is Nothing

If Not dict Is Nothing Then
  ' not nothing 
End If

IsNot Nothing

If dict IsNot Nothing Then
  ' not nothing 
End If

IsNothing function(VB)

If Not IsNothing(dict) Then
  ' not nothing 
End If

I wouldn't use the VB6 function IsNothing in .NET anymore since it introduces unneeded dependencies and for the reason mentioned here (it allows value types and always returns False).

edited Dec 23 '14 at 20:33

answered Nov 11 '13 at 09:53

Tim Schmelter

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If Not does not appear in Workflow foundation dotnet 4.5 – Sajeetharan Nov 11 '13 at 10:00
3

@Sajeetharan: `Not` is the logical negation operator and it's available since VB.NET 1.0. – Tim Schmelter Nov 11 '13 at 10:01

How to check dictionary is null in VB.NET?

1 Answers1