Connection Error in login page in C# with SQL

private void btnLogin_Click(object sender, EventArgs e)
        {
            int t = 0;
            SqlConnection conn = new SqlConnection("Data Source=DONUT-90CF4E6F4\SQLEXPRESS;Initial Catalog=Resort;Integrated Security=True");
            conn.Open();
            SqlCommand cmd = new SqlCommand("select * from AdminLogin", conn);
            SqlDataReader dr= cmd.ExecuteReader();
            dr.Read();
            try
            {
                do
                {
                    if (textBox1.Text.Equals((dr.GetString(0)).ToString()) && textBox2.Text.Equals((dr.GetString(0)).ToString()))
                    {
                        t = 1;
                    }
                    
                } while (dr.Read());
            }
            catch(Exception ex)
            {
                MessageBox.Show(ex.Message);
            }
            finally
            {
                conn.Close();
                dr.Close();
            }
            if (t == 1)
            {
                Form2 WelAdmin = new Form2();
                WelAdmin.Show();
                this.Hide();
            }
            else
            {
               MessageBox.Show("UserName and Password did not match! Try Again...");
                
            }
      }