Can I use an extension method with a Structure in VB.NET?

Question

I am wondering whether I can use DataContractJsonSerializer to serialize a Structure type, or does it have to be a reference/Class type?

I have the following code:

<Extension()> Public Function ToJSON(ByVal target As Object) As String
    Dim serializer = New System.Runtime.Serialization.Json.DataContractJsonSerializer(target.GetType)
    Using ms As MemoryStream = New MemoryStream()
        serializer.WriteObject(ms, target)
        ms.Flush()

        Dim bytes As Byte() = ms.GetBuffer()

        Dim json As String = Encoding.UTF8.GetString(bytes, 0, bytes.Length).Trim(Chr(0))

        Return json
    End Using
End Function

And yet if I call it on a Structure type, such as a KeyValuePair(Of T1, T2), I get the following error:

Public member 'ToJSON' on type 'KeyValuePair(Of String,Object)' not found.

Answer 1

The error message does not have anything to do with DataContractJsonSerializer or anything inside your method. It cannot find the method itself. That suggests to me that you have forgotten to add a reference to the namespace in which this extension method is defined. I apologise I don’t know the VB equivalent, but in C# it is the using clause I’m talking about.