How can I cancel a Form_Load?

Question

How do I write a application that create a code. I want if a user open the application a other user don't can use the application and get a MessageBox with the username who use the application. For this I use a Form_Load event with try catch and it works. The second user get a message with the name of the other user but the form open after this. I want that the form not open after this message.

my code:

private void Form1_Load(object sender, EventArgs e)
{
    try
    {
        var stream = File.Open("lock", FileMode.OpenOrCreate,FileAccess.Read);
        global_stream = stream;

        string username = User.GetUsername();
        string machine =  Computer.GetMachineName();

        TextDatei datei = new TextFile();

        datei.WriteFile("user_log", "Username: " + username + " Invoicennumber: "
            + machine); 

        CreateCode();

    }
    catch (Exception)
    {
        TextFile file = new TextFile();
        string info = datei.ReadFile("user_log");

        MessageBox.Show(info);

        Application.Exit();
    }
}

Answer 1

I'd make the loading of the form itself conditional instead of canceling it:

try
{
    // Do your validation stuff here...

    // The form will only show if the validation didn't throw.
    Application.Run(new Form1());
}
catch (Exception)
{
    TextFile file = new TextFile();
    string info = datei.ReadFile("user_log");

    MessageBox.Show(info);
}

This is more efficient since the loading of the form is skipped altogether.

Answer 2

I won't comment on what you're doing...

...but to close the form is simple:

    private void Form1_Load(object sender, EventArgs e)
    {                       
        Boolean someCondition = true; //whatever check you're doing

        if (someCondition)
        {
            MessageBox.Show("Some Condition Met");
            this.Close();
        }
        else
        {
            this.InitialiseTheFormEtc();
        }
    }

Answer 3

One suggestion for you, You could do the necessary loading at Init() itself and close the form there itself than Load(). That's the way better to go with.

this.Close();