Change the JSON to a JSON array

Question

In my VB.net Web Api, I am using JsonWriter to build a Json Array then pass it to Client Side as a list(Of VerifyReturn) considering VerifyReturn is the name of a class.

  Public Class VerifyReturn
    Public Property Name as String
    Public Property AnotherName as String
  End Class

Here's my VB.net code:

  Dim sb As New StringBuilder()
  Dim sw As New StringWriter(sb)
  jsonWriter.WriteStartObject()

  jsonWriter.WritePropertyName("Name")
  jsonWriter.WriteValue("Value")
  jsonWriter.WritePropertyName("AnotherName")
  jsonWriter.WriteValue("AnotherValue")

  jsonWriter.WriteEndObject()
  Dim ReturnJson = JsonConvert.DeserializeObject(Of List(Of VerifyReturn))(sb.ToString)

I am getting this error:

Cannot deserialize the current JSON object (e.g. {"name":"value"}) into type 'System.Collections.Generic.List`1[EFramework.VerifyReturn]' because the type requires a JSON array (e.g. [1,2,3]) to deserialize correctly.

To fix this error either change the JSON to a JSON array (e.g. [1,2,3]) or change the deserialized type so that it is a normal .NET type (e.g. not a primitive type like integer, not a collection type like an array or List) that can be deserialized from a JSON object. JsonObjectAttribute can also be added to the type to force it to deserialize from a JSON object.

I am new and just learning JSON.

I would like to change the JSON to a JSON array.

How can I do this?

Thanks.

Kevin Sandow · Accepted Answer · 2014-05-30 08:18:53Z

JSON doesn't allow associative arrays, thus objects are used.

In JSON your example is

{"Name":"Value","AnotherName":"AnotherValue"}

Assuming you want an array with each property as an object that would look like:

[{"Name":"Value"},{"AnotherName","AnotherValue"}]

And your code would look like:

Dim sb As New StringBuilder()
Dim sw As New StringWriter(sb)
jsonWriter.WriteStartArray()

jsonWriter.WriteStartObject()
jsonWriter.WritePropertyName("Name")
jsonWriter.WriteValue("Value")
jsonWriter.WriteEndObject()

jsonWriter.WriteStartObject()
jsonWriter.WritePropertyName("AnotherName")
jsonWriter.WriteValue("AnotherValue")
jsonWriter.WriteEndObject()

jsonWriter.WriteEndArray()

Dim ReturnJson = JsonConvert.DeserializeObject(Of List(Of DifferentClass))(sb.ToString)

Alternatively, if you need a list of your your class, then only wrap an array around it:

Dim sb As New StringBuilder()
Dim sw As New StringWriter(sb)
jsonWriter.WriteStartArray()

jsonWriter.WriteStartObject()
jsonWriter.WritePropertyName("Name")
jsonWriter.WriteValue("Value")

jsonWriter.WritePropertyName("AnotherName")
jsonWriter.WriteValue("AnotherValue")
jsonWriter.WriteEndObject()

jsonWriter.WriteEndArray()

Dim ReturnJson = JsonConvert.DeserializeObject(Of List(Of VerifyReturn))(sb.ToString)

This should result in:

[{"Name":"Value", "AnotherName","AnotherValue"}]

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