CODEWITHSUNDEEP
c#winformscenteringmdi
Your_Unequal
Your_Unequal

Reputation: 246

Display dialog box in center of MDI Child

Disclaimer: I know answers have already been provided for a similar question however these do not appear to be working for me.

I have an application which uses a main form with an MDIClient; I want to show a dialog which allows the user to enter a value; this dialog is to show in the center of the MDIChild form from which the dialog is called.

I have already looked at the following solution:

C# - Show Dialog box at center of its parent

However, unless there is an application-related discrepancy with my solution, this seems to have some fundamental issues.

It is suggested that the following would achieve this:

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

This however, has the following issue:

When I try and implement this, when stepping through the code, as soon as it hits the line to set the form Parent, the following exception occurs:

Top-level control cannot be added to a control.

N.B. Unless all Forms initialise with a TopLevel value of true, this value doesn't seem to be set anywhere!

Okay, so; we'll set the TopLevel to false to allow the Parent form to be set as the Parent of the dialog. Assuming I do this, when it hits the line to ShowDialog():

Form that is not a top-level form cannot be displayed as a modal dialog box. Remove the form from any parent form before calling showDialog.

And therein lies my quagmire; the dialog form seems to NEED to NOT be a TopLevel form in order to have a Parent but then simultaneously needs to be a TopLevel form so it can be shown as a dialog...

Final note, I do not think I should have to set the 'StartPosition' of the form that I want to have as the dialog as this is already set in the InitializeComponent() part of the form; nevertheless, I've tried explicitly setting this in the function and it makes no difference.

Upvotes: 1

Views: 1458

Answers (1)

CoolBots
CoolBots

Reputation: 4879

You can position the dialog form manually:

    private void invokeDialogButton_Click(object sender, EventArgs e)
    {
        var dialogForm = new DialogForm();
        dialogForm.StartPosition = FormStartPosition.Manual;

        //Get the actual position of the MDI Parent form in screen coords
        Point screenLocation = Parent.PointToScreen(Parent.Location);

        //Adjust for position of the MDI Child form in screen coords
        screenLocation.X += Location.X;
        screenLocation.Y += Location.Y;

        dialogForm.Location = new Point(screenLocation.X + (Width - dialogForm.Width) / 2, 
                                        screenLocation.Y + (Height - dialogForm.Height) / 2);

        dialogForm.ShowDialog(this);
    }

Take a look at this working example project on my Github page (Visual Studio 2015 Community Edition project).

Upvotes: 2

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