C# 如何将ImageSource转换为bool
我有C# 如何将ImageSource转换为bool,c#,wpf,xaml,ivalueconverter,C#,Wpf,Xaml,Ivalueconverter,我有Image和按钮SaveToDisk。所以,当未加载图像时(ImageSource为空)-我需要阻止SaveToDisk按钮。反之亦然 所以,我决定使用转换器。但这对我不起作用: public class SourceToEnableConverter:IValueConverter { public object Convert(object value, Type targetType, object parameter, System.Globalization.Cultur
Image
和按钮SaveToDisk
。所以,当未加载图像时(ImageSource为空)-我需要阻止SaveToDisk
按钮。反之亦然
所以,我决定使用转换器。但这对我不起作用:
public class SourceToEnableConverter:IValueConverter
{
public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
if ((ImageSource)value == null) return false;
return true;
}
public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
return Binding.DoNothing;
}
}
Xaml:
和WPF XAML图像:
<Image Name="imIcon" Grid.Row="1" Grid.Column="2"
HorizontalAlignment="Left" VerticalAlignment="Center" Margin="8,0,0,8"
>
<Image.Source>
<Binding Path="ObjectViewModel.Image" >
<!--<Binding.TargetNullValue>
<Image Source="Empty.png"></Image>
</Binding.TargetNullValue>-->
</Binding>
</Image.Source>
</Image>
按钮:
<Button Name="btnSaveIcon" Click="btnSaveIcon_Click"
Grid.Row="1" Grid.Column="0" Grid.ColumnSpan="6" Margin="8,0,0,8"
HorizontalAlignment="Left" VerticalAlignment="Center"
Content="SaveAs"}"
Height="44"
IsEnabled="{Binding ElementName=imIcon,Path=Source,Converter={StaticResource SourceToEnableConverter}}"
/>
看起来null不是ImageSource的有效值。
试着改变
if ((ImageSource)value == null) return false;
到
我会使用命令
。使用CanExecute
方法确定按钮是否已启用,如下所示:
XAML
如果CanExecute
为true
,则您的按钮将被启用。命令的真正好处在于,您可以在菜单和几乎任何控件上重用它们,而按钮的单击事件仅对按钮有效
我通常会使用一个DataContext
,但是为了显示命令的使用,我认为这样做会很好。更简单:返回值!=无效代码>
System.Windows.Data Error: 23 : Cannot convert '<null>' from type '<null>' to type 'System.Windows.Media.ImageSource' for 'ru-RU' culture with default conversions; consider using Converter property of Binding. NotSupportedException:'System.NotSupportedException
if ((ImageSource)value == null) return false;
if (value == null) return false;
<Window x:Class="ImageDemo.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:local="clr-namespace:ImageDemo"
mc:Ignorable="d"
Title="MainWindow" Height="350" Width="525">
<Window.Resources>
<RoutedCommand x:Key="LoadImage"/>
<RoutedCommand x:Key="UnloadImage"/>
</Window.Resources>
<Window.CommandBindings>
<CommandBinding Command="{StaticResource LoadImage}" CanExecute="LoadImage_CanExecute" Executed="LoadImage_Executed"/>
<CommandBinding Command="{StaticResource UnloadImage}" CanExecute="UnloadImage_CanExecute" Executed="UnloadImage_Executed"/>
</Window.CommandBindings>
<DockPanel Margin="5">
<Image x:Name="imgPlaceholder" Height="100" Width="100" DockPanel.Dock="Top"/>
<StackPanel Orientation="Horizontal" Margin="5" HorizontalAlignment="Center" VerticalAlignment="Top">
<Button Content="Load Image" HorizontalAlignment="Center" VerticalAlignment="Center" Margin="10" Command="{StaticResource LoadImage}"/>
<Button Content="Unload Image" HorizontalAlignment="Center" VerticalAlignment="Center" Margin="10" Command="{StaticResource UnloadImage}"/>
</StackPanel>
</DockPanel>
</Window>
public partial class MainWindow : Window
{
public BitmapImage bitmap;
public MainWindow()
{
InitializeComponent();
bitmap = new BitmapImage();
bitmap.BeginInit();
bitmap.UriSource = new Uri("C:\\Temp\\the_ugly_baby.jpg", UriKind.Absolute);
bitmap.EndInit();
imgPlaceholder.Source = null;
}
private void LoadImage_Executed(object sender, ExecutedRoutedEventArgs e)
{
imgPlaceholder.Source = bitmap;
}
private void LoadImage_CanExecute(object sender, CanExecuteRoutedEventArgs e)
{
e.CanExecute = imgPlaceholder.Source == null ? true : false;
}
private void UnloadImage_CanExecute(object sender, CanExecuteRoutedEventArgs e)
{
e.CanExecute = imgPlaceholder.Source != null ? true : false;
}
private void UnloadImage_Executed(object sender, ExecutedRoutedEventArgs e)
{
imgPlaceholder.Source = null;
}
}