I wrote some code to access the id form table dbo.details by using user email id stored in session, but I get this error
The multi-part identifier "abc@gmail.com" could not be bound

I have used the built-in server of Visual Studio 2017.

This is my code:

protected void Page_Load(object sender, EventArgs e)
{
        if (Session["user"] == null)
        {
            Response.Write("<script>alert('you have to login to Checkout!')</script>");
            Response.Redirect("login.aspx");
        }
        else
        {
            string S1 = Convert.ToString(Session["user"].ToString());

            SqlConnection scon = new SqlConnection(ConfigurationManager.ConnectionStrings["ConnectionString"].ConnectionString);
            String myquery = "select ID from dbo.details where email=" + S1;

            SqlCommand cmd = new SqlCommand();
            cmd.CommandText = myquery;
            cmd.Connection = scon;

            SqlDataAdapter da = new SqlDataAdapter();
            da.SelectCommand = cmd;

            DataSet ds = new DataSet();
            da.Fill(ds);

            int details_id = Convert.ToInt32(ds.Tables[0].Rows[0][0].ToString());
            Response.Write(details_id);
        }
}

I have checked all the names and they are ok.

I don't know what to do now!