Set image runtime in VisualBrush with c#

问题

actually I set an image took from the resources at designtime into the xaml file like this:

<Button Click="btnLogin_Click" Name="btnLogin">
    <StackPanel Orientation="Horizontal">
        <Rectangle Width="20" Height="20" Name="recLogin">
            <Rectangle.Resources>
                <SolidColorBrush x:Key="BlackBrush" Color="White" />
            </Rectangle.Resources>
            <Rectangle.Fill>
                <VisualBrush Stretch="Fill" Visual="{StaticResource appbar_user}" x:Name="brushLogin" />
            </Rectangle.Fill>
        </Rectangle>
        <TextBlock Text=" login" Name="txbLogin" />
    </StackPanel>
</Button>

and works fine. But (is a login button) I wish that when the user do a login, the image on the button (inside a rectangle) will be changed..

How can I do?

回答1:

You can use a DataTrigger to change the image when a property updates in your model.

In this example the boolean value IsLoggedIn is changed which in turn changes the image.

Example:

Xaml:

<Window x:Class="WpfApplication1.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="MainWindow" Height="125.078" Width="236.441" Name="UI" >
    <Window.Resources>

        <VisualBrush x:Key="Loggedin">
            <VisualBrush.Visual>
                <Image Source="http://icons.iconarchive.com/icons/deleket/sleek-xp-basic/32/Ok-icon.png" Stretch="Uniform" />
            </VisualBrush.Visual>
        </VisualBrush>

        <VisualBrush x:Key="NotLoggedin">
            <VisualBrush.Visual>
                <Image Source="http://icons.iconarchive.com/icons/deleket/sleek-xp-basic/32/Close-2-icon.png" Stretch="Uniform" />
            </VisualBrush.Visual>
        </VisualBrush>

    </Window.Resources>

    <Grid DataContext="{Binding ElementName=UI}">
        <Button Click="btnLogin_Click" Name="btnLogin" HorizontalAlignment="Left" Width="94" Height="40" VerticalAlignment="Top" Margin="63,26,0,0">
            <StackPanel Orientation="Horizontal">
                <Rectangle Width="20" Height="20" Name="recLogin">
                    <Rectangle.Resources>
                        <SolidColorBrush x:Key="BlackBrush" Color="White" />
                    </Rectangle.Resources>
                    <Rectangle.Style>
                        <Style TargetType="{x:Type Rectangle}">
                            <Setter Property="Fill" Value="{StaticResource NotLoggedin}" />
                            <Style.Triggers>
                                <DataTrigger Binding="{Binding IsLoggedIn}" Value="True">
                                    <Setter Property="Fill" Value="{StaticResource Loggedin}" />
                                </DataTrigger>
                            </Style.Triggers>
                        </Style>
                    </Rectangle.Style>
                </Rectangle>
                <TextBlock Text=" login" Name="txbLogin" />
            </StackPanel>
        </Button>
    </Grid>
</Window>

Code:

public partial class MainWindow : Window, INotifyPropertyChanged
{
    private bool _isLoggedIn;

    public MainWindow()
    {
        InitializeComponent();  
    }

    public bool IsLoggedIn
    {
        get { return _isLoggedIn; }
        set { _isLoggedIn = value; NotifyPropertyChanged("IsLoggedIn"); }
    }

    private void btnLogin_Click(object sender, RoutedEventArgs e)
    {
        IsLoggedIn = !IsLoggedIn;
    }

    public event PropertyChangedEventHandler PropertyChanged;
    private void NotifyPropertyChanged(string property)
    {
        if (PropertyChanged != null)
        {
            PropertyChanged(this, new PropertyChangedEventArgs(property));
        }
    }
 }

Note: I just used online images as I dont have your ressources, you can change to suit your needs

Result:

IsLoggedIn = false;