Hi ramco1917,
Please refer below sample.
HTML
<asp:Label ID="lblData" runat="server"></asp:Label>
Code
C#
protected void Page_Load(object sender, EventArgs e)
{
    string id = "321483788811";
    string orderId = "NMBC0001789312";
    string body = "{" + string.Format(@"""awbs"" : {2}[""{0}"",{2}""{1}""{2}]", id, orderId, Environment.NewLine) + "}";
    lblData.Text = body;
}
VB.Net
Protected Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs) Handles Me.Load
    Dim id As String = "321483788811"
    Dim orderId As String = "NMBC0001789312"
    Dim body As String = "{" & String.Format("""awbs"" : {2}[""{0}"",{2}""{1}""{2}]", id, orderId, Environment.NewLine) & "}"
    lblData.Text = body
End Sub
Output
{"awbs" : ["321483788811", "NMBC0001789312" ]}