can some one help by giving code for login

We are here to help you with code you have written, not write code for you. What have you written?

private void loginbtnbtn_Click(object sender, EventArgs e)

            SqlConnection con = new SqlConnection();
            string str = "Integrated Security=SSPI;Persist Security Info=False;Initial Catalog=cardb;Data Source=SAIDATTA-051EA8\\SQLEXPRESS";
            con.ConnectionString = str;
            string query = "select  * from carlogin where empcode='" + textBox1.Text + "'";//textBox1=employeid
            SqlCommand cmd = new SqlCommand(query, con);

            SqlDataReader dr;

            dr = cmd.ExecuteReader();
            while (dr.Read())
                string pwd = Convert.ToString(dr[1]);//textBox2=password

                if ((textBox2.Text == pwd) )
                    MessageBox.Show("YOU ARE LOGGED IN AS ADMIN");
                    MDIParent2 m1 = new MDIParent2();// MDIParent2 is form for parent

                else if ((textBox2.Text == pwd) )
                    MessageBox.Show("YOU ARE LOGGED IN AS AS STAFF");
                    MDIParent1 m = new MDIParent1();// MDIParent1 is form for staff

                    MessageBox.Show(" invalid  username or password");


table are in following formate

create table carlogin ( username varchar(40) canstraint primary key(username),password varchar(30) )