int temp = Convert.ToInt32(com.ExecuteScalar().ToString());

SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["connect"].ConnectionString);
con.Open();

string checkuser = "select * from tb_Login where Username='" + txtUsername.Text + "' and Password='" + txtPassword.Text + "' ";

SqlCommand com = new SqlCommand(checkuser, con);

int temp = Convert.ToInt32(com.ExecuteScalar().ToString());
con.Close();

if (temp == 1)
{
    con.Open();
    string checkPass = "select Password from tb_Login where Username='" + txtUsername.Text + "'";

    SqlCommand passCom = new SqlCommand(checkPass, con);
    string password = passCom.ExecuteScalar().ToString().Replace(" ", "");

    if (password == txtPassword.Text)
    {
        Session["New"] = txtUsername.Text;
        Response.Write("Correct");
    }
    else
    {
        Response.Write("Not Correct");
    }
}
else
{
    Response.Write("Username not correct");
}

string checkuser = "select * from tb_Login where Username='" + txtUsername.Text + "' and Password='" + txtPassword.Text + "' ";

int temp = Convert.ToInt32(com.ExecuteScalar().ToString());