Show a child form in the centre of Parent form in C

Question

I create a new form and call from the parent form as follows      loginForm   new SubLogin       loginForm Show      I need to display the child form at the centre of the parent  So in the child form load I do the foll    Point p   new Point this ParentForm Width   2 - this Width   2  this ParentForm Height   2 - this Height   2   this Location   p    But this is throwing error as parent form is null  I tried setting the Parent property as well  but didn t help  Any inputs on this

User · Answer

If you want to calculate your own location, then first set StartPosition to FormStartPosition.Manual:

Form Child = new Form();
Child.StartPosition = FormStartPosition.Manual;
Child.Location = new Point(Location.X + (Width - Child.Width) / 2, Location.Y + (Height - Child.Height) / 2);
Child.Show(this);

Where this is the main/parent form, just like Location.X.

Default value for StartPosition is FormStartPosition.CenterParent and therefore it changes the child's location after showing.

User · Answer

Assuming your code is running inside your parent form  then something like this is probably what you re looking for   loginForm   new SubLogin    loginForm StartPosition   FormStartPosition CenterParent loginForm Show this     For the record  there s also a Form CenterToParent   function  if you need to center it after creation for whatever reason too

User · Answer

When you want to use a non-blocking window  show   instead of showDialog     this not work     not work with  Show this  but only with  ShowDialog this  loginForm StartPosition   FormStartPosition CenterParent  loginForm Show this     In this case  you can use this code to center child form before display the form     this   the parent frmDownloadPercent frm   new frmDownloadPercent    frm Show this     this   the parent form   here the tips frm Top   this Top     this Height   2  -  frm Height   2    frm Left   this Left     this Width   2  -  frm Width   2

User · Answer

You need this   Replace Me with this parent  but you need to set parent before you show that form     Private Sub   berToolStripMenuItem Click ByVal sender As System Object  ByVal e As System EventArgs  Handles   berToolStripMenuItem Click           About StartPosition   FormStartPosition Manual                 About Location   New Point Me Location X   Me Width   2 - About Width   2  Me Location Y   Me Height   2 - About Height   2          About Show       End Sub

User · Answer

Make a Windows Form   then put option for it   CenterParent then use this Code    yourChildFormName x   new yourChildFormName    x ShowDialog

User · Answer

There seems to be a confusion between  Parent  and  Owner   If you open a form as MDI-form  i e  imbedded inside another form  then this surrounding form is the Parent  The form property StartPosition with the value FormStartPosition CenterParent refers to this one  The parameter you may pass to the Show method is the Owner  not the Parent  This is why frm StartPosition   FormStartPosition CenterParent does not work as you may expect   The following code placed in a form will center it with respect to its owner with some offset  if its StartPosition is set to Manual  The small offset opens the forms in a tiled manner  This is an advantage if the owner and the owned form have the same size or if you open several owned forms   protected override void OnShown EventArgs e        base OnShown e       if  Owner    null  amp  amp  StartPosition    FormStartPosition Manual            int offset   Owner OwnedForms Length   38      approx  10mm         Point p   new Point Owner Left   Owner Width   2 - Width   2   offset  Owner Top   Owner Height   2 - Height   2   offset           this Location   p

User · Answer

When launching a form inside an MDIForm form you will need to use  CenterScreen instead of  CenterParent   FrmLogin f   new FrmLogin    f MdiParent   this  f StartPosition   FormStartPosition CenterScreen  f Show

User · Answer

Why not use this    LoginForm WindowStartupLocation   Windows WindowStartupLocation CenterOwner     vb net

User · Answer

You can set the StartPosition in the constructor of the child form so that all new instances of the form get centered to it s parent   public MyForm         InitializeComponent         this StartPosition   FormStartPosition CenterParent      Of course  you could also set the StartPosition property in the Designer properties for your child form   When you want to display the child form as a modal dialog  just set the window owner in the parameter for the ShowDialog method   private void buttonShowMyForm Click object sender  EventArgs e        MyForm form   new MyForm        form ShowDialog this

User · Answer

protected override void OnLoad EventArgs e            base OnLoad e            CenterToParent

User · Answer

On the SubLogin Form I would expose a SetLocation method so that you can set it from your parent form   public class SubLogin   Form      public void SetLocation Point p             this Location   p            Then  from your main form   loginForm   new SubLogin       Point p     do math to get point loginForm SetLocation p   loginForm Show

User · Answer

If any windows form child form  is been opened from a new thread of Main window parent form  then its not possible to hold the sub window to the center of main window hence we need to fix the position of the sub window manually by means of X and Y co-ordinates   In the properties of Subwindow change the  StartPosition  to be  Manual   code in main window  private void SomeFunction         Thread m Thread   new Thread LoadingUIForm       m Thread Start        OtherParallelFunction        m Thread Abort       private void LoadingUIForm         m LoadingWindow   new LoadingForm this       m LoadingWindow ShowDialog        code in subwindow for defining its own position by means of parent current position as well as size  public LoadingForm Control m Parent       InitializeComponent       this Location   new Point  m Parent Location X  m Parent Size Width 2 - this Size Width 2                                 m Parent Location Y  m Parent Size Height 2 - this Size Height 2                                     Here the co-ordinates of center of parent is calculated as well as the subwindow is kept exactly at the center of the parent by calculating its own center by  this height 2  and  this width 2  this function can be further taken for parent relocated events also

User · Answer

Try   loginForm StartPosition   FormStartPosition CenterParent  loginForm ShowDialog this     Of course the child for will now be a blocking form  dialog  of the parent window  if that isn t desired then just replace ShowDialog with Show    loginForm Show this     You will still need to specify the StartPosition though

User · Answer

The setting of parent does not work for me unless I use form ShowDialog      When using form Show     or form Show this   nothing worked until I used  this CenterToParent     I just put that in the Load method of the form  All is good   Start position to the center of parent was set and does work when using the blocking showdialog

User · Answer

If you have to center your childForm  from childForm then the code will be something like this  This code is in the childForm cs   this Show parent as Form         I received the parent object as Object type this CenterToParent

User · Answer

It works in all cases  swap Form1 for your main form   Popup popup   new Popup    popup StartPosition   System Windows Forms FormStartPosition Manual  popup Location   new System Drawing Point  Form1 ActiveForm Location X   Form1 ActiveForm Width   2  -  popup Width   2   Form1 ActiveForm Location Y   Form1 ActiveForm Height   2  -  popup Height   2    popup Show Form1 ActiveForm

User · Answer

childform   new Child    childform Show this     In event childform load  this CenterToParent

User · Answer

As a sub form i think it s not gonna Start in the middle of the parent form  until you Show it as a Dialog              Form2 ShowDialog     i was about to make  About Form  and this is perfect that s i am searching for  and untill you close the About form you cant Touch click  anythings of parents Form once you Click for About Form  in my case   Coz its Showing as Dialog

User · Answer

The parent probably isn t yet set when you are trying to access it   Try this   loginForm   new SubLogin    loginForm Show this   loginForm CenterToParent

[c#] Show a child form in the centre of Parent form in C#

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