Close child form if already open

How can I go abou开发者_开发百科t closing a Child form if it's already open? And if it isn't already open, then open it?

Thank you

I already have this code, which doesn't work, obviously:

Form ibx = new inbox();
if(ibx.Visible)
ibx.Dispose();
else
ibx.Show();

All that the above does is creates a new form whether or not it's already open.

private Form frm;
public void ToggleForm() {
  if(frm == null) {
    frm = new Form();
    frm.Show();
  }
  else {
    frm.Close();
    frm = null;
  }
}

If what you want to achieve is opening a form only if it isn't already open, then bring it on front when it is, then the following code might help.

private void tsmiMenuOption_Click(object sender, EventArgs e) {
    // Assuming this method is part of an MDI form.
    foreach(Form child in this.MdiChildren)
        if (child.Name == MyForm.Name) {
            child.BringToFront();
            return;
        }

    MyForm f = new MyForm();
    f.MdiParent = this;
    f.Show();
}

So, this is untested pseudo-c#-code that verifies if MyForm is already opened and contained in the MdiContainer.Children. If it is, then it brings this form (MyForm) to the front. If it is not, then it simply instantiate and opens it.

Is this about what you want?

In your main form, when you create the first childform, keep a reference to it. Currently you're creating a new childform every time you run that code and then you check if the newly created form is visible.

Also be aware that your subject talk about opening and closing but your code seems to just be dealing with hiding and showing.

Carra's code is a good sample how to do it, but be careful if the childform can be closed from anywhere else.

You need to keep a reference to ibx. Your code creates a new inbox everytime it's run.

Module Module1

Public Function InstanceNewForm(ByRef ParentForm As Form, ByRef Childform As Form) As Boolean

    Dim bOpen As Boolean = False
    Dim frm As Form

    For Each frm In ParentForm.MdiChildren
        If Childform.Name = frm.Name Then
            Childform.Focus()
            bOpen = True
            Exit For
        End If
    Next

    If Not bOpen Then
        With Childform
            .StartPosition = FormStartPosition.CenterScreen
            .MdiParent = Parentform
            .Show()
        End With
    End If

    frm = Nothing

    Return bOpen

End Function

End Module

The above code will check to see if a mdi form is already loaded in the parent container and if its already active will set the focus to it. Otherwise it will create the mdi form.

Just call it from anywhere the mdi form needs to be loaded. ex: call InstanceNewForm(me,form2)

Works like a charm everytime!!