按下鼠标左键时更改鼠标光标？

Question

I need to change the mouse cursor while the left mouse button is pressed. Unfortunately changes to the mouse cursor are ignored until the left mouse button is released. Is there any workaround to this? Thanks for any hint!

(I'm using WPF and C#)

EDIT:

Sample Project: http://cid-0432ee4cfe9c26a0.skydrive.live.com/self.aspx/%c3%96ffentlich/WpfApplication5.zip (just run it, instructions are shown in the application)

Code for the sample:

XAML:

<Window x:Class="WpfApplication5.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Title="MainWindow" Height="350" Width="695" Loaded="Window_Loaded">
<Grid>
    <Button Content="Button1" Height="287" HorizontalAlignment="Left" Margin="12,12,0,0" Name="button1" VerticalAlignment="Top" Width="235" />
    <Button Content="Button2" Height="287" HorizontalAlignment="Left" Margin="284,12,0,0" Name="button2" VerticalAlignment="Top" Width="278" MouseMove="button2_MouseMove" />
</Grid>

Window class:

public partial class MainWindow : Window
{
    public MainWindow()
    {
        InitializeComponent();
    }

    private void button2_MouseMove(object sender, MouseEventArgs e)
    {
        Cursor = Cursors.Cross;
    }

    private void Window_Loaded(object sender, RoutedEventArgs e)
    {
        button1.Content="Step1: Left click on this button, \nhold down the left mouse button";
        button2.Content = "(Make sure you don't hover this\n button before hovering Button1.\n Default application cursor\n is the normal arrow cursor)\n\n Step 2: Keep on holding the left mouse \nbutton, hover this button\n\nThe cursor won't change. (It will change after the \nleft mouse button was released)";
    }
}

Answer 1

I would recommend using Preview* events where possible for visual changes, as it will keep your logic nicely separated. Also, it is best (IMHO) to use the Mouse.OverrideCursor property to change the cursor temporarily.

For example:

void Window_Loaded(object sender, RoutedEventArgs e)
{
    // ...
    button1.PreviewMouseLeftButtonDown += Button1_PreviewMouseLeftButtonDown;
    button1.PreviewMouseLeftButtonUp += Button1_PreviewMouseLeftButtonUp;
}

void Button1_PreviewMouseLeftButtonDown(object sender, MouseButtonEventArgs e)
{
    Mouse.OverrideCursor = Cursors.Cross;
    Mouse.Capture(button1);
}

void Button1_PreviewMouseLeftButtonUp(object sender, MouseButtonEventArgs e)
{
    Mouse.Capture(null);
    Mouse.OverrideCursor = null;
}

Answer 2

In left mouse down handler you can have following code.

try
{
   Cursor = Cursors.WaitCursor;
}
catch(Exception ex)
{
}
finally
{
   Cursor = Cursors.Default;
}

You can reset to Default cursor as per your requirement.