Hi nauna,

Refer below code.

Namespaces

C#

using Newtonsoft.Json;
using Newtonsoft.Json.Linq;

VB.Net

Imports Newtonsoft.Json
Imports Newtonsoft.Json.Linq

Code

C#

string array = "[[\"A\",null],[\"B\",null],[\"C\",\"D\"],[\"E\",\"F\"]]";
JArray jArray = JsonConvert.DeserializeObject<JArray>(array);
for (int i = 0; i < jArray.Count; i++)
{
    JArray jArray1 = JsonConvert.DeserializeObject<JArray>(jArray[i].ToString());
    string key = ((JValue)jArray1[0]).Value == null ? "" : ((JValue)jArray1[0]).Value.ToString();
    string value = ((JValue)jArray1[1]).Value == null ? "" : ((JValue)jArray1[1]).Value.ToString();
}

VB.Net

Dim array As String = "[[""A"",null],[""B"",null],[""C"",""D""],[""E"",""F""]]"
Dim jArray As JArray = JsonConvert.DeserializeObject(Of JArray)(array)

For i As Integer = 0 To jArray.Count - 1
    Dim jArray1 As JArray = JsonConvert.DeserializeObject(Of JArray)(jArray(i).ToString())
    Dim key As String = If((CType(jArray1(0), JValue)).Value Is Nothing, "", (CType(jArray1(0), JValue)).Value.ToString())
    Dim value As String = If((CType(jArray1(1), JValue)).Value Is Nothing, "", (CType(jArray1(1), JValue)).Value.ToString())
Next