How to access WithdrawChecking() in LoginForm inside MainTransactionForm

//in MainTransactionForm.Xaml.cs
public partial class MainTransactionForm : Form
{
    public MainTransactionForm()
    {
        InitializeComponent();
    } 

    private void withdrawButton_Click(object sender, EventArgs e)
    {
        LoginForm loginForm = new LoginForm();
        loginForm.WithdrawChecking();
    }
}

//in LoginForm.Xaml.cs
class LoginForm
{
    public void WithdrawChecking()
    {
        if(true)
        {
            MessageBox.Show("withdraw checking");
        }
    }
}