Login code for c#.net

Login code three ways in c#.net

first method:

private void Loginbutton_Click(object sender, EventArgs e)

        {

            con.Open();

          

            SqlDataAdapter da=new SqlDataAdapter("select * from login where username='"+txtusername .Text .Trim ()+"' and password='"+txtpassword .Text .Trim ()+"'",con);

            DataTable dt=new DataTable ();

            da.Fill (dt);

            if(dt.Rows.Count >0)

            {

                Form1 fr=new Form1 ();

                fr.ShowDialog ();

            }

            else

            {

                MessageBox .Show ("please enter correct formate");

            }

        }

Second method:

private void LoginButton_Click(object sender, EventArgs e)

        {

            try

            {

                SqlDataAdapter da = new SqlDataAdapter("select * from login where username='" + txtuser_name.Text.Trim() + "' and password='" + txt_password.Text.Trim() + "'", con);

                DataTable dt = new DataTable();

                da.Fill(dt);

                int count = dt.Rows.Count;

                if (count == 0)

                {

                    MessageBox.Show("Invalid user name and password");

                    txt_password.Text = "";

                    txtuser_name.Text = "";

                }

                else if (count == 1)

                {

                    Form2 fr = new Form2();

                    fr.ShowDialog();

                    txt_password.Text = "";

                    txtuser_name.Text = "";

                }

            }

            catch (Exception er)

            {

                MessageBox.Show(er.Message);

            }

        }

Third Method:

 protected void ImageButton1_Click(object sender, ImageClickEventArgs e)

    {

        con.Open();

        if (TextBox3.Text != "" && TextBox4.Text != "")

        {

            SqlCommand cmd = new SqlCommand("select * from AdminLogin where Pwd = '" + TextBox4.Text + "'and  UName = '" + TextBox3.Text + "'", con);

            SqlDataReader dr = cmd.ExecuteReader();

            dr.Read();

            if (dr.HasRows)

            {

               Form2 fr = new Form2();

                    fr.ShowDialog();

                    TextBox3.Text = "";

                   TextBox4.Text = "";

            }

            else

            {

                MessageBox.Show("Invalid user name and password");

TextBox3.Text = "";

                   TextBox4.Text = "";

            }

        }

    }