How do you center your main window in WPF?

I have a WPF application and I need to know how to center the wain window programatically (not in XAML).

I need to be able to do this both at startup and in response to certain user events. It has to be dynamically calculated since the window size itself is dynamic.

What's the simplest way to do this? Under old Win32 code, I'd call the system metrics functions and work it all out. Is that still the way it's done or is the开发者_Go百科re a simple CenterWindowOnScreen() function I can now call.

Well, for startup time, you can set the startup location:

window.WindowStartupLocation = WindowStartupLocation.CenterScreen;

Later, you'll need to query it. The information (at least for the primary screen) is available via SystemParameters.PrimaryScreenWidth/Height.

private void CenterWindowOnScreen()
{
    double screenWidth = System.Windows.SystemParameters.PrimaryScreenWidth;
    double screenHeight = System.Windows.SystemParameters.PrimaryScreenHeight;
    double windowWidth = this.Width;
    double windowHeight = this.Height;
    this.Left = (screenWidth / 2) - (windowWidth / 2);
    this.Top = (screenHeight / 2) - (windowHeight / 2);
}

You can use this method to set the window position to the center of your screen.

Isn't it just as simple to set

WindowStartupLocation="CenterScreen"

In the XAML definition for the window.

I had to combine a few of these answers to cover all bases in my case:

• Peter's method to find the current monitor - rather than the just the Primary monitor (seriously who has just 1 monitor at work anymore?)
• @Wild_A's method to use the workarea rather than the screen bounds to take into account the space for the taskbar.
• I had to add DPI scaling, specifically for a tablet displaying 1280x800 as 1024x640, but which is useful to cover edge cases, for which I found an answer for here. Note the dpiScaling variable is null if called on first load before the UI is displayed (explained here)

//get the current monitor
Screen currentMonitor = Screen.FromHandle(new System.Windows.Interop.WindowInteropHelper(Application.Current.MainWindow).Handle);

//find out if our app is being scaled by the monitor
PresentationSource source = PresentationSource.FromVisual(Application.Current.MainWindow);
double dpiScaling = (source != null && source.CompositionTarget != null ? source.CompositionTarget.TransformFromDevice.M11 : 1);

//get the available area of the monitor
Rectangle workArea = currentMonitor.WorkingArea;
var workAreaWidth = (int)Math.Floor(workArea.Width*dpiScaling);
var workAreaHeight = (int)Math.Floor(workArea.Height*dpiScaling);

//move to the centre
Application.Current.MainWindow.Left = (((workAreaWidth - (myWindowWidth * dpiScaling)) / 2) + (workArea.Left * dpiScaling));
Application.Current.MainWindow.Top = (((workAreaHeight - (myWindowHeight * dpiScaling)) / 2) + (workArea.Top * dpiScaling));

where myWindowWidth and myWindowHeight are variables I used to manually set the size of the window earlier.

Rect workArea = System.Windows.SystemParameters.WorkArea;
this.Left = (workArea.Width - this.Width) / 2 + workArea.Left;
this.Top = (workArea.Height - this.Height) / 2 + workArea.Top;

This takes into account the taskbar size (by using System.Windows.SystemParameters.WorkArea) and position (by adding workArea.Left and workArea.Top)

In case you need to draw a window in an multiple screen environment. I've made a static class where the following method can be re-used:

public static void PostitionWindowOnScreen(Window window, double horizontalShift = 0, double verticalShift = 0)
{
    Screen screen = Screen.FromHandle(new System.Windows.Interop.WindowInteropHelper(window).Handle);
    window.Left = screen.Bounds.X + ((screen.Bounds.Width - window.ActualWidth) / 2) + horizontalShift;
    window.Top = screen.Bounds.Y + ((screen.Bounds.Height - window.ActualHeight) / 2) + verticalShift;        
}

In the constructor of the Window now just call the method:

this.Loaded += (s, a) => Globals.PostitionWindowOnScreen(this, 0, 0)

As a basic solution, you can use the window's StartupLocation property, set it to one of the enum values defined in System.Windows.WindowStartupLocation enumeration, there is one for center of screen:

_wpfWindow.StartupLocation = System.Windows.WindowStartupLocation.CenterScreen;

Unfortunately it's not always quite so simple; you need to account for multiple monitors, taskbars, etc. The "CenterScreen" option opens the window in the center of the screen that has the mouse cursor. See this SO question for a lot of information, or reference the api.

In the window element just add this attribute-value pair: WindowStartupLocation="CenterScreen"

What I am using in my app, it is working for multiple displays and for different DPI setting

    //center a window on chosen screen
    public static void CenterWindow(Window w, System.Windows.Forms.Screen screen = null)
    {
        if(screen == null)
            screen = System.Windows.Forms.Screen.PrimaryScreen;

        int screenW = screen.Bounds.Width;
        int screenH = screen.Bounds.Height;
        int screenTop = screen.Bounds.Top;
        int screenLeft = screen.Bounds.Left;

        w.Left = PixelsToPoints((int)(screenLeft + (screenW - PointsToPixels(w.Width, "X")) / 2), "X");
        w.Top = PixelsToPoints((int)(screenTop + (screenH - PointsToPixels(w.Height, "Y")) / 2), "Y");
    }

    public static double PixelsToPoints(int pixels, string direction)
    {
        if (direction == "X")
        {
            return pixels * SystemParameters.WorkArea.Width / System.Windows.Forms.Screen.PrimaryScreen.WorkingArea.Width;
        }
        else
        {
            return pixels * SystemParameters.WorkArea.Height / System.Windows.Forms.Screen.PrimaryScreen.WorkingArea.Height;
        }
    }

    public static double PointsToPixels(double wpfPoints, string direction)
    {
        if (direction == "X")
        {
            return wpfPoints * System.Windows.Forms.Screen.PrimaryScreen.WorkingArea.Width / SystemParameters.WorkArea.Width;
        }
        else
        {
            return wpfPoints * System.Windows.Forms.Screen.PrimaryScreen.WorkingArea.Height / SystemParameters.WorkArea.Height;
        }
    }

Another short way to make mainwindow render at center of the computer screen using code behind.

this.Left = (System.Windows.SystemParameters.PrimaryScreenWidth - this.Width)/2;
this.Top = (System.Windows.SystemParameters.PrimaryScreenHeight - this.Height)/2;

Based on @Wild_A answer I just subscribed to the SizeChanged event, and added this event handler:

private void Window_SizeChanged(object sender, SizeChangedEventArgs e)
{
    try
    {
        Rect workArea = SystemParameters.WorkArea;
        this.Left = (workArea.Width - e.NewSize.Width) / 2 + workArea.Left;
        this.Top = (workArea.Height - e.NewSize.Height) / 2 + workArea.Top;
    }
    catch (Exception ex) { ... Handel exception; }
}

Just use:

WindowStartupLocation="CenterScreen"

And in case you only want to center horizontally / vertically, You can override the OnActivated method and set left or top to zero like this:

    protected override void OnActivated(EventArgs e)
    {
        base.OnActivated(e);

        // to center Vertically
        Left = 0;
        // or user top = 0 to center Horizontally
        //top = 0;
    }

Go to property window of MainWindow.xaml

• find WindowStartupLocation property from Common category
• select CenterScreen option from dropdown
• Run the Application

For Full Screen

Go to property window of MainWindow.xaml

• find WindowState property from Common category
• select Maximized option from dropdown
• Run the Application

Copy-paste good quality extension code.

Runtime:

using System;
using System.Windows;
using System.Windows.Forms;
using System.Windows.Interop;

namespace Extensions
{
    /// <summary>
    /// <see cref="Window"/> extensions.
    /// </summary>
    public static class WindowExtensions
    {
        /// <summary>
        /// Moves the window to the center of the current screen, also considering dpi.
        /// </summary>
        /// <param name="window"></param>
        /// <exception cref="ArgumentNullException"></exception>
        public static void MoveToCenter(this Window window)
        {
            window = window ?? throw new ArgumentNullException(nameof(window));

            var helper = new WindowInteropHelper(window);
            var screen = Screen.FromHandle(helper.Handle);
            var area = screen.WorkingArea;

            var source = PresentationSource.FromVisual(window);
            var dpi = source?.CompositionTarget?.TransformFromDevice.M11 ?? 1.0;

            window.Left = dpi * area.Left + (dpi * area.Width - window.Width) / 2;
            window.Top = dpi * area.Top + (dpi * area.Height - window.Height) / 2;
        }
    }
}

Initial position:

<Window WindowStartupLocation="CenterScreen">
</Window>

You will have to find this line : Title="MainWindow" Height="450" Width="800"

And you add this line to it : WindowStartupLocation="CenterScreen"

To become this : Title="MainWindow" Height="450" Width="800" WindowStartupLocation="CenterScreen">

Thank me Later ♥

If you it to be maximized at once
this.WindowState = System.Windows.WindowState.Maximized;