C# How do I handle a one time startup condition for a form if the form is generated new each time?

问题

I have form A, which opens form B after an event then hides itself. Form B generates conditions for form A then returns to form A and closes itself; however, due to conflict with code, I will have to generate form A anew lest I encounter a stackoverflow exception / my application not closing properly (due to form A, the main form, being hidden)

This has gotten a bit confusing, essentially I've already solved this by declaring the main form as new each time, however, I wish to be able to handle first time startup events like those tutorial messages for certain applications. Without the overhead of having to create a log to store my boolean, how will I detect if it's the first time the form is opened?

Normally I would:

Event(){
  bool startup;
  if (startup = true) {
  startup = false;
  return;
  }
  //Rest of code
}

However, since the form is generated new each time, this will always remain true.

Here's the code:

Form A variables:

 Account AccountForm = new Account();

Button event:

        AccountForm.QR = this;
        this.Hide();
        AccountForm.ShowDialog();

Form B:

public Form QR { get; set; }

Button event:

    QR = new QueryRefiner();
    this.QR.Show();
    this.Close();

This is all of it I think. I take the new declaration out of QR, and I would receive a StackOverflow exception. I guess I should have created a new question for this, but there it is. (I think i'm on the timer still)

回答1:

Well,an easy solution is to make a new constructor in your FormA to get a parameter indicating that it is created from FormB, something like:

public FormA(bool byFormB)
{
    if (byFormB)
    {
        //do what you have to do when it's created from FormB
    }
}

And just create it like this from FormB: FormA frm=new FormA(true);

Anyway, I would not create a new FormA each time, just hide/show it.

回答2:

Here's one way to do it: Expose a public property in your FormB that holds a reference to a FormA. When you create an instance of FormB from FormA, set the reference to point to FormA. Then, in the Form_Closing() event of FormB, show the FormA.

You can also expose public properties and/or methods on your FormA so that FormB can pass on any information it gathered back to FormA before it exits:

public partial class FormB : Form
{
    public FormA formToShowOnClose { get; set; }

    private void FormB_FormClosing(object sender, FormClosingEventArgs e)
    {
        if (formToShowOnClose != null)
        {
            formToShowOnClose.TableName = txtTableName.txt;
            formToShowOnClose.LoadData();
            formToShowOnClose.Show();
        }
    }

    // Other form B code here...
}

public partial class FormA : Form
{
    public string TableName { get; set; }

    public void LoadData()
    {
        // Do something with TableName here
    }

    private void button1_Click(object sender, EventArgs e)
    {
        var formB = new FormB();
        formB.formToShowOnClose = this;
        this.Hide();
        formB.Show();
    }

    // Other form A code here...
}

来源：https://stackoverflow.com/questions/43446753/c-sharp-how-do-i-handle-a-one-time-startup-condition-for-a-form-if-the-form-is-g

标签

forms

boolean

startup