DataTable table = new DataTable();
string jsonArrayText = "[{'a':'a1','b':'b1'},{'a':'a2','b':'b2'}]";
private void button1_Click(object sender, EventArgs e)
{
    //Deserialize to array
    JArray array = JsonConvert.DeserializeObject(jsonArrayText) as JArray;
    if (array.Count > 0)
    {
        StringBuilder columns = new StringBuilder();
        JObject objColumns = array[0] as JObject;
        //Structure header
        foreach (JToken jkon in objColumns.AsEnumerable<JToken>())
        {
            string name = ((JProperty)(jkon)).Name;
            columns.Append(name + ",");
            table.Columns.Add(name);
        }
        //Add data to the table
        for (int i = 0; i < array.Count; i++)
        {
            DataRow row = table.NewRow();
            JObject obj = array[i] as JObject;
            foreach (JToken jkon in obj.AsEnumerable<JToken>())
            {

                string name = ((JProperty)(jkon)).Name;
                string value = ((JProperty)(jkon)).Value.ToString();
                row[name] = value;
            }
            table.Rows.Add(row);
        }
    }
}