Please where do I put declare statement in my C# window?

DECLARE @userId INT

INSERT INTO User (Email, Pass, ....) VALUES ('aaaa@gmail.com', 'pass',.......)

SET @userId = @@IDENTITY

INSERT INTO Wallet (Uid, amount) VALUES (@MYID,0)

My C# window:

using System;
using System.Collections.Generic;
using System.Data;
using System.Web.Security;
using System.Xml.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Data.SqlClient;

public partial class DashBoard : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
     
    }

    protected void Button1_Click(object sender, EventArgs e)
    {

    }
}