Cannot Json deserialize Youtube data with VB.net

Question

I need to obtain the \"title\" from the response i get from Youtube. I get the following error at line 8, position 12, that is, at line:

\"items\": [
         


        

Answer 1

You are getting that exception because you have declared several auto-implemented array properties incorrectly. As shown in Auto-Implemented Properties (Visual Basic) such properties should be declared as follows, with the () array indicator as part of the return type:

Public Property items As Item()

Instead you declare them as follows:

Public Property items() As Item

This declares a property returning a single Item rather than an array of them. The () attached to the property name is optional; for parameterless properties it is redundant but for properties taking parameters the argument list appears there. See the documentation page Property Statement for details. Then Json.NET throws the exception you see when attempting to deserialize a JSON array into one of the non-array properties in your model.

To fix this, three of your classes should be modified as follows:

Public Class Rootobject
    Public Property kind As String
    Public Property etag As String
    Public Property pageInfo As Pageinfo

    Public Property items As Item()   ' Fixed 

End Class

Public Class Snippet
    Public Property publishedAt As Date
    Public Property channelId As String
    Public Property title As String
    Public Property description As String
    Public Property thumbnails As Thumbnails
    Public Property channelTitle As String

    Public Property tags As String()   ' Fixed 

    Public Property categoryId As String
    Public Property liveBroadcastContent As String
    Public Property localized As Localized
End Class

Public Class Regionrestriction

    Public Property allowed As String()   ' Fixed 

End Class

Then, since the items are an array, to access the titles and put then in a list, you can use extension methods from System.Linq.Enumerable:

' Convert the json string to RootObject.
Dim root = JsonConvert.DeserializeObject(Of Rootobject)(json)

' Extract the list of titles.
Dim titles = root.items _
    .Select(Function(i) i.snippet.title) _
    .ToList()

' Get the first title in the list.
Dim firstTitle = titles.FirstOrDefault()

Console.WriteLine("First title = ""{0}""", firstTitle)

Which prints out First title = "Blur - Song 2".

Sample VB.Net fiddle.