How to create login form with functional decentralization users in winform

try
 {
     if (txtUserName.Text == "" || txtPassword.Text == "")
     {
         MessageBox.Show("Entry Username and Password", "Error");
         txtUserName.Focus();
         return;
     }
     else
     {
         SqlConnection conn = new SqlConnection(@"Data Source=; Initial Catalog=; uid = sa; pwd = 123456;");
         conn.Open();
         SqlCommand cmd = new SqlCommand("Select Pass From Account Where UserName ='" + txtUserName.Text + "'", conn);
         SqlDataReader reader = cmd.ExecuteReader();
         reader.Read();
         if (txtPassword.Text == reader.GetValue(0).ToString())
         {
             MessageBox.Show("Login success!", "Success");
             reader.Close();
             conn.Close();
             this.Hide();
             Form2 frm2 = new Form2();
             frm2.ShowDialog();
         }
         else
         {
             MessageBox.Show("Wrong password", "Error");
             txtPassword.Focus();
         }
         reader.Close();
         conn.Close();
     }
 }
 catch (Exception)
 {
     MessageBox.Show("Wrong Username or Password", "Error");
     txtUserName.Focus();
 }

if (txtPassword.Text == reader.GetValue(0).ToString())
               {
                   MessageBox.Show("Login success!", "Success");
                   reader.Close();
                   conn.Close();
                   this.Hide();
                   //I need assistance in this paragraph
                   //if (user == admin) open form 1
                   // else open form 2
               }