Single instance C#Class

Question

I have a Windows Form with the following code:

public partial class frmCadastroPessoaFisica : Form
{
    public frmCadastroPessoaFisica()
    {
        InitializeComponent();
    }
}

I would like to create only one instance of this form.

Some answers on the subject in stackoverflow say to use the Singleton standard:

public class Singleton
{
    private static Singleton instance;

    private Singleton() { }

    public static Singleton Instance
    {
        get
        {
            if (instance == null)
                lock (typeof(Singleton))
                    if (instance == null) instance = new Singleton();

            return instance;
        }
    }
}

source: linhadecodigo.com.br

Already others say that using Singleton for this would be exaggeration.

What is the correct way to allow only one instance of this form?

Answer 1

There are several ways to ensure that only one instance of your class is invoked. Your example contains one of them, called Singleton Factory.

Another possibility is via static definition, as in the example below:

public static class Instances
{
    public static frmCadastroPessoaFisica frmCadastroPessoaFisica;

    static Instances()
    {
        frmCadastroPessoaFisica = new frmCadastroPessoaFisica();
    }
}

You can access the static instance via Instances.frmCadastroPessoaFisica.