datetime format in asp.net

hi friends,

now display in Label1 date in this format

4/3/2012 10:44:42 PM

but

i want to display like this in label1 from database

2012-04-03 22:44:42.000


OpenConnection(con);
cmd.Connection = con;

SqlDataAdapter da = new SqlDataAdapter("select top 1 calldate from data", con);
DataTable dt = new DataTable();
da.Fill(dt);

if (dt.Rows.Count > 0)
{
Label1.Text = dt.Rows[0][0].ToString();

}
else
{
Label1.Text = "No Records found!";
}
con.Close();





please give the code for it,


thanks.