如何从另一个表单刷新一个表单？

Question

I have two forms- form1 and form2. I call form2 from form1 using the below snippet:

Application.run(new Form2());

Form2 f2=new Form2();

f2.show();

This code is working absolutely fine and i could see the form2 loading from form1.

Now i need to repeat this for say 5 times. When i run it for 1st time, New istance has to be created ( ie above code has to be executed) but when i run it for 2nd/3rd or 4th time, i need to refresh the form2 instead of creating a new form2. When i run the above code for 5 times, 5 new instances of form2 are created. Instead the form2 has to be displayed only once but it has to be refreshed when i call anyother time other than the first form. Can you please throw some light on this?

Answer 1

. When i run the above code for 5 times, 5 new instances of form2 are created. Instead the form2 has to be displayed only once but it has to be refreshed when i call anyother time other than the first form.

This is because you create it 5 times:

 Form2 f2=new Form2();

This create a new Form. If you call it 5 times it will create 5 instances of form.

If you want to refresh the data, you need to create a public method "Refresh()" and call it. For example:

f2.Refresh();

This way, you will be able to redo the binding or set again the data you want to refresh for the persistence.

Answer 2

you can try like this ....

please note that this is only a rudimentary implementation of a Mediator pattern. I would highly encourage you to read up about that pattern, and design patterns in general in order to gain a better understanding of what is going on.

Again, this is a sample, but it does have some basic error checking and should get you going.

Your form declaration is going to look something like this:

public partial class MainForm : Form
{
    private FormMediator _formMediator;

    public MainForm()
    {
        InitializeComponent();
    }

    public void SomeMethodThatOpensTheSubForm()
    {
        SubForm subForm = new SubForm();

        _formMediator = new FormMediator(this, subForm);

        subForm.Show(this);
    }
}

And the modified implementation of the Mediator would look like this:

public class FormMediator
{
    private Form _subForm;
    private Form _mainForm;

    public FormMediator(Form mainForm, Form subForm)
    {
        if (mainForm == null)
            throw new ArgumentNullException("mainForm");

        if (subForm == null)
            throw new ArgumentNullException("subForm");

        _mainForm = mainForm;
        _subForm = subForm;

        _subForm.FormClosed += MainForm_FormClosed;
    }

    void MainForm_FormClosed(object sender, FormClosedEventArgs e)
    {
        try
        {
            _mainForm.Refresh();
        }
        catch(NullReferenceException ex)
        {
            throw new InvalidOperationException("Unable to close the Main Form because the FormMediator no longer has a reference to it.", ex);
        }
    }
}

I hope it helps you....