how to create a login page in asp.net using datatable

SqlConnection cnn = new SqlConnection(Pass your Connection string);

SqldataAdapter da = new SqldataAdapter("Select * from users where username = '" +txtusername.text+ "' and password = '" +txtpwd.text+ "' ",cnn);

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

if(ds.Tables[0].Rows.Count !=0)
{
      Session["username"] = ds.Tables[0].Rows[0][2].ToString();
      Responce.Redirect("Default.aspx");
}