Show Dialog box at center of its parent

Question

It's been a mess to show a DialogBox at the center of its parent form. Here is a method to show a dialog.

I am positioning its parent to center but not able to center the DialogBox

private void OpenForm(Object point, Object height, Object width)
{
    FormLoading frm = new FormLoading();
    Point temp = (Point)point;
    Point location = new Point(temp.X + (int)((int)width) / 2, 
                               temp.Y + (int)((int)height) / 2);
    frm.Location = location;
    frm.ShowDialog();
}

private void btnView_Click(object sender, EventArgs e)
{
    try
    {                    
        ThreadStart starter= delegate { OpenForm(currentScreenLocation, 
                                                 this.Height, this.Width); };
        Thread t = new Thread(starter);
        t.Start();
        ////// Some functionality here...
        t.Abort();
    }
    catch (Exception)
    {
    }
}

I would also be careful with multithreading. Control's properties (at least those that deal with the User interface) can only be changed from the thread on which they are created. I don't see a bigger picture here so I don't know why you create each form in it's own thread, but keep that in mind. — Kornelije Petak, Jul 07 '11 at 07:07

Kornelije Petak · Accepted Answer · 2011-07-07T06:53:21.100

119

You might want to check the Form.StartPosition property.

http://msdn.microsoft.com/en-us/library/system.windows.forms.form.startposition.aspx

something along the lines of:

private void OpenForm(Form parent)
{
    FormLoading frm = new FormLoading();
    frm.Parent = parent;
    frm.StartPosition = FormStartPosition.CenterParent;
    frm.ShowDialog();
}

This of course requires setting the form's parent.

edited Jul 07 '11 at 06:53

answered Jul 07 '11 at 06:37

Kornelije Petak

9,412
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frm.StartPosition = FormStartPosition.Manual; frm.Location = location; I used it and worked for me :) – Tausif Khan Jul 07 '11 at 09:12
Setting it to FormStartPosition.CenterParent does the math for you. But I guess you would want to retain your code if you plan on doing anything more complex than centering. I'm glad you solved your problem. – Kornelije Petak Jul 07 '11 at 09:15
FormStartPosition.CenterParent did not work for me. I just want to center it. But your provided link was a key for me. Thanks for that – Tausif Khan Jul 07 '11 at 09:22
23

`frm.Parent = parent;` doesn't work, but removing that line of code still works properly.. the parent thing gives a Top-Level error which couldn't be fixed. `Top-level control cannot be added to a control` – SSpoke Jul 02 '13 at 23:53
rather than `frm.Parent = parent`, I use `frm.Parent = this` – Jim Lahman Feb 06 '14 at 14:26
6

If you get the 'Top-Level control cannot be added...' exception try setting the Owner instead: `frm.Owner = parent;` – Nils Lande Jun 03 '15 at 07:55
You can also pass the parent window to ShowDialog – Patrick Feb 07 '18 at 05:21
@Nils +1 for `frm.Owner` as this works within the child form class. – Mooseman Oct 24 '18 at 17:44

score 14 · Answer 2 · edited Feb 13 '13 at 21:55

14

form1.StartPosition = FormStartPosition.CenterScreen;

See http://msdn.microsoft.com/en-us/library/system.windows.forms.form.startposition(v=vs.110).aspx

edited Feb 13 '13 at 21:55

Andrew Barber

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answered Feb 13 '13 at 21:52

user2070102

157
1
2

score 6 · Answer 3 · answered Jan 30 '18 at 07:43

6

if you are making a custom MessageBox,you can simply put this:

CenterToParent();

in your custom MessageBox formload() method.

answered Jan 30 '18 at 07:43

Mohsen K

257
4
10

score 4 · Answer 4 · answered Apr 26 '13 at 09:02

In addition, if you want to set up arbitrary location you can use this

FormLoading frm = new FormLoading();
Point location = new Point(300, 400);
frm.StartPosition = System.Windows.Forms.FormStartPosition.Manual;
frm.Location = location;
frm.ShowDialog();

score 3 · Answer 5 · edited Oct 27 '16 at 22:27

3

NewForm.Show();

NewForm.Top = (this.Top + (this.Height / 2)) - NewForm.Height / 2;
NewForm.Left = (this.Left + (this.Width / 2)) - NewForm.Width / 2;

edited Oct 27 '16 at 22:27

LarsTech

80,625
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answered Oct 27 '16 at 22:22

Billy Xd

79
5

Show Dialog box at center of its parent

5 Answers5

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