How can i show my main WPF window after successful login?

Question

I started learning WPF recently and I am trying to write a simple login system.

I got it to "work", it is verifing if the credentials are correct according to the database i made and returning successful, but i couldn't make it open the main window after the login.

Can anyone help?

This is the login click event

private void LoginButton_Click(object sender, RoutedEventArgs e)
    {
        if (con.State == System.Data.ConnectionState.Open)
        {
            con.Close();
        }
        if(VerifyUser(textBoxUser.Text, textBoxPassword.Password))
        {
            MessageBox.Show("Login Succeded", "Login", MessageBoxButton.OK, MessageBoxImage.Information);
            this.Close();
            
        }
        else
        {
            MessageBox.Show("User or Password invalid", "Error", MessageBoxButton.OK, MessageBoxImage.Error);
        }
    }

And this is the verify user code

private bool VerifyUser(string username, string password)
    {
        con.Open();
        com.Connection = con;
        com.CommandText = "select Usuario_Cod from tblUsuario where Usuario_Nome='"+username+"' and Usuario_Senha='"+password+"'";
        dr = com.ExecuteReader();
        if (dr.Read())
        {
            if(Convert.ToBoolean(dr["Usuario_Cod"]) == true)
            {
                return true;
            }
            else
            {
                return false;
            }
        }
        else
        {
            return false;
        }
    }

My exact problem is that i don't know what kind of code i have to add to make it show my main window after the login window is closed in case of success

Example: user should only get access to the main window if he provides a valid username and password

Login Window and Main Window

Answer 1

I got it to work adding the following:

private void LoginButton_Click(object sender, RoutedEventArgs e)
    {
        if (con.State == System.Data.ConnectionState.Open)
        {
            con.Close();
        }
        if(VerifyUser(textBoxUser.Text, textBoxPassword.Password))
        {
            MessageBox.Show("Login Succeded", "Login", MessageBoxButton.OK, MessageBoxImage.Information);
            Sistema sistema = new Sistema();
            sistema.Show();
            this.Close();
            
        }
        else
        {
            MessageBox.Show("User or Password invalid", "Error", MessageBoxButton.OK, MessageBoxImage.Error);
        }
    }