1

Is it okay to place "view = new Person" within the button event handler? If I don't, and I place it within the Form1 constructor, only my last value gets added. Is that the proper way if I want to declare a new instance and then add it to my Arraylist?

    private ArrayList store;

    public Form1()
    {
        InitializeComponent();
        store = new ArrayList();
    }

    private void Form1_Load(object sender, EventArgs e)
    { }

    private void button1_Click(object sender, EventArgs e)
    {
        //Is it okay to declare a new instance of the Person class 
        // with each button push?            
        Person view = new Person();
        view.firstname = txtFirstName.Text;
        view.lastname = txtLastName.Text;
        store.Add(view);
        txtFirstName.Clear();
        txtLastName.Clear();   
    }

    private void button2_Click(object sender, EventArgs e)
    {
        foreach (Person display in store)
        {
            MessageBox.Show(display.ToString());
        }
    }
4

2 に答える 2

5

Is it okay to place "view = new Person" within the button event handler?

Yes. If your goal is to make a new person each time you click the button, this is appropriate to do.

On a side note: You should consider using List<Person> instead of ArrayList. This is the newer, type-safe list class (as of .NET 2.0), and far nicer to use.

于 2012-08-14T19:03:42.377 に答える
0

This looks like exactly what you're supposed to do.

I suppose you read somewhere that you should avoid doing complex things like instantiating objects in a form's event handlers. That sounds like a pattern of application design called "Model-view-controller", and to implement it you would have a class, separate from your WinForm here, that contains the logic that should be performed when a button is clicked, and the Form's controls are instead linked to this Controller's method instead of the form containing its own handlers. It has its advantages, but for the average small project it's not necessary. Keep doing what you're doing, it's perfectly fine.

A couple things: first, unless you're coding in .NET 1.1, ArrayList is generally not a good thing. Beginning in .NET 2.0, a concept called generics was introduced to the language, and one of the primary things generics allow you to do is specify the type of object that a collection can contain. The System.Collections.Generics.List<T> class is a better choice for store if all it will store is People; change the declaration to private List<Person> store;. The advantages of using a generic collection are that code that needs to get objects back out will know what type the objects are, because the collection will prohibit adding objects of a different type to it.

Second, name your buttons when you put them in the designer, before you define event handlers. Code should be self-documenting, and a button named "button1" doesn't tell us what it's supposed to do. If you had instead named this button "CreatePersonButton" after dragging it from the Toolbox onto the Form, when you double-clicked it to define its behavior, the event handler would be named "CreatePersonButton_Click" which is much more descriptive.

于 2012-08-14T19:12:07.210 に答える