Access form control from other form

Question

I got the following method in my MDIparent1

public void Disablebutton()
{
    toolStripButton1.Enabled = false;
}

In my LoginForm OKButton click

MDIParent1 f1 = new MDIParent1();
f1.Disablebutton();
this.Close();

The LoginForm is Modal of MDIparent1.

Problem is the Disablebutton() don't works in LoginForm

What about it doesn't work? Does toolStripButton1 exist in LoginForm? You probably need to direct Disablebutton to work on the toolStripButton1 which exists inside LoginForm - there is a way to do this, but want to confirm that's your issue first. — NWard, Jul 25 '13 at 18:14

score 2 · Answer 1 · answered Jul 25 '13 at 18:16

2

You're creating a new instance of MDIParent1 and not using the actual instance that opened LoginForm. You could pass the parent into the LoginForm constructor.

private MDIParent1 _parentForm = null;
public LoginForm(MDIParent1 parentForm)
{
   _parentForm = parentForm;
}

//then in whichever event you're using
_parentForm.Disablebutton();
this.Close();

When you want to show the LoginForm form, pass in the MDIParent1 form.

//assuming this is in MDIParent1.cs (otherwise pass the form instance variable)
using(LoginForm lf = new LoginForm(this))
{
   lf.Show();
}

answered Jul 25 '13 at 18:16

keyboardP

68,824
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is that same thing with LoginForm lf = new LoginForm(); lf.ShowDialog();? – Karlx Swanovski Jul 25 '13 at 18:20
`ShowDialog` will make the parent form inaccessible until the child form is closed (it's a modal window). `Show` will allow both forms to be accessed so you can use `ShowDialog` instead if that's what you want. As an alternative to the above approach, you can set `lf.MdiParent = this` and then access the `MdiParent` property as mentioned in the other answers. – keyboardP Jul 25 '13 at 18:24
does not contain a constructor that takes 0 arguments, cannot convert from App.MainForm to App.MDIParent1 – Karlx Swanovski Jul 25 '13 at 18:26
Did you use `LoginForm lf = new LoginForm(this)`? – keyboardP Jul 25 '13 at 18:27
I tried to use LoginForm lf = new LoginForm(this) and got same error – Karlx Swanovski Jul 25 '13 at 18:30
Instead of `this`, pass in your `MDIParent1` object, it seems you're calling the form from another place other than `MDIParent1.cs`. – keyboardP Jul 25 '13 at 18:30
I use exactly that code. NUllReferenceException was unhandle Object reference not set to an instance of an object – Square Ponge Jul 25 '13 at 18:34
@SquarePonge - I didn't realise you were using two different accounts, I thought you weren't OP. What's null? – keyboardP Jul 26 '13 at 00:00

score 1 · Answer 2 · answered Jul 25 '13 at 18:20

From what I understand of your code, you are creating a new MDIParent1 window and calling DisableButton on the newly created MDIParent1 window. You have to call DisableButton on the form owning LoginForm (via the MdiParent property).

Edit: someone beat me to it.

score 0 · Answer 3 · answered Jul 25 '13 at 18:20

0

You should do this in your MDIchild form

  if(this.MdiParent is  LoginForm)
  {
     (this.MdiParent as LoginForm).Disablebutton();
  }

answered Jul 25 '13 at 18:20

Ehsan

31,833
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Access form control from other form

3 Answers3