public class SQLcon

    {

        private string con = "server=(local);user id=sa;password=sa;database=student";



        public SqlConnection ConnectToDatabase()

        {

            return new SqlConnection(con);

        }

        public bool Login(string uid, string pwd, SqlConnection mycon)     //判断是否登陆成功

        {

            if (mycon.State != ConnectionState.Open)

            {

                MessageBox.Show("数据库未打开");

                try

                {

                    mycon.Open();

                    SqlCommand login = new SqlCommand();

                    string str = " select UserID from UserLogin where UserName='" + uid + "' and PassWord ='" + pwd + "' ";

                    login.CommandText = str;

                    login.Connection = mycon;

                    SqlDataReader result = login.ExecuteReader();

                    mycon.Close();

                    if (result.HasRows)

                    {

                        return true;

                    }

                    else

                    {

                        return false;

                    }

                }