How to handle errors during Json parse?

Question

I'm parsing Json and it could happen that a key is null, so I want to create an exception for a

NullReferenceException: Object Reference not set to an instance of an object

The code I'm using is:

Dim jsonResponse As JsonNode
               Using http As HttpClient = New HttpClient
                   Dim url As String = url 
                   jsonResponse = JsonNode.Parse(http.GetStreamAsync(url).Result)

               End Using

               Dim result = jsonResponse("result").AsObject
               Dim c As String = ""


               For Each kvp In result.AsEnumerable
                       Dim records = kvp.Value("records").AsArray
                       For Each r In records
                       Dim side As String = r("side").AsValue.ToString
                        next

Sometimes, the key "records" doesn't contain numbers, but it could be :null instead, so the software throw that error. How can I handle the error to keep running the code? Thanks

Answer 1

Hi @Mattia Fanti ,
You can prevent this exception by adding predicates in front.

            If kvp.Value("records") IsNot Nothing Then  
                Dim records = kvp.Value("records").AsArray  
                For Each r In records  
                    Dim side As String = r("side").AsValue.ToString  
                Next  
            End If  

Or use the Try Catch statement to handle this exception.

            Try  
                Dim records = kvp.Value("records").AsArray  
                For Each r In records  
                    Dim side As String = r("side").AsValue.ToString  
                Next  
            Catch ex As System.NullReferenceException  
            Console.WriteLine(ex.Message)  
            End Try  

Hope this could be helpful.
Best Regards.
Jiachen Li

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