C＃奇怪的WPF组合框行为

Question

I have simple window. This is what happens when I click ComboBox: List appears in upper left corner of screen instead of under Combobox.

XAML:

<Window x:Class="WpfPortOfTestingCamera.VideoSettings"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="Video Settings" WindowStartupLocation="CenterOwner" ResizeMode="NoResize" ShowInTaskbar="False" mc:Ignorable="d" xmlns:d="http://schemas.microsoft.com/expression/blend/2008" xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" SizeToContent="WidthAndHeight" d:DesignHeight="167">
    <StackPanel Name="stackPanel1" VerticalAlignment="Top" HorizontalAlignment="Center">
        <GroupBox Header="Settings" Name="groupBox1">
            <Grid Name="grid1" VerticalAlignment="Center" HorizontalAlignment="Center">
                <Grid.ColumnDefinitions>
                    <ColumnDefinition Width="80*" />
                    <ColumnDefinition Width="175*" />
                </Grid.ColumnDefinitions>
                <Grid.RowDefinitions>
                    <RowDefinition />
                    <RowDefinition />
                </Grid.RowDefinitions>
                <Label Content="Resolution:" Height="28" Name="label1" Margin="0" HorizontalAlignment="Left" VerticalAlignment="Center" />
                <Label Content="Framerate:" Height="28" HorizontalAlignment="Left" Margin="0" Name="label2" VerticalAlignment="Center" Grid.Row="1" />
                <ComboBox Grid.Column="1" Height="23" HorizontalAlignment="Left" Margin="0" Name="comboBox1" VerticalAlignment="Center" Width="150" SelectionChanged="comboBox1_SelectionChanged" />
                <ComboBox Height="23" HorizontalAlignment="Left" Margin="0" Name="comboBox2" VerticalAlignment="Center" Width="150" Grid.Column="1" Grid.Row="1" SelectionChanged="comboBox2_SelectionChanged" />
            </Grid>
        </GroupBox>
        <Label Name="labelSelectedSize" Content="Size @ FPS" />
        <Button Name="button1" Content="Apply" Click="button1_Click" />
    </StackPanel>
</Window>

Answer 1

与其直接在Loaded事件中直接打开它，不如在Dispatcher上排队另一个消息以将其打开。

Answer 2

I ran into exactly this and just posted an example at WPF ComboBox DropDown part appears in the wrong place which worked for me. The interested reader can go there to peruse my commentary, but here's the snippet (NOTE: WindoBaseLoadedHandler is the "Loaded=" handler specified in the XAML):

protected void WindowBaseLoadedHandler(object sender, RoutedEventArgs e)
{

...non-essential lines of code removed...

    if (DataContext != null)
    {
        Dispatcher.BeginInvoke(DispatcherPriority.Normal, new Action(() =>
        {
            this.IsEnabled = false;

            LoginDlg loginDlg = new LoginDlg();
            loginDlg.ShowDialog();

            if (!loginDlg.Success)
            {
                /*-----------------------------------
                 * Log on failed -- terminate app...
                 *----------------------------------*/
                ...termination logic removed...
            }

            this.IsEnabled = true;
        }));
    }