如何设置FallbackValue作为路径外部图像文件的约束力？

问题描述

我想设置FallbackValue的情况下，当我转换器不能打电话，但我不知道该怎么做。

 ＆lt;图像来源={结合FallbackValue =图片/ Unknown.png，路径= LatestPosition.DeviceFamily，转换器= {X：静态CONV：ConverterSet.DeviceTypeToImageSourceconverter}} NAME =此搜索拉伸=填充保证金=5,8WIDTH =150HEIGHT =150Grid.RowSpan =4/＆GT;
 

在转换器外部图像

路径看起来像当LatestPosition！= NULL图像被以适当的方式设置。

 私有静态只读的ImageSource装置1 =新的BitmapImage（新的URI（/图片/ dev1.png，UriKind.Relative））;
私人静态只读的ImageSource DEV2 =新的BitmapImage（新的URI（/图片/ dev2.png，UriKind.Relative））;
 

解决方案

有关Image控件，当你与一个URI字符串绑定的源属性，它会自动转换URI为BitmapImage的。
但是，如果你设置FallbackValue和TargetNullValue为URI字符串，
它不会显示。

您需要将其设置为BitmapImage的：

 ＆LT; Window.Resources＆GT;
    ＆LT;的BitmapImage X：键=DefaultImageUriSource =/资源;组件/图片/ Default.jpg/＆GT;
＆LT; /Window.Resources>＆lt;图像宽度=128
               高度=128
               的Horizo​​ntalAlignment =左
               VerticalAlignment =顶部
               来源={结合照片，FallbackValue = {StaticResource的DefaultImage}，
                                TargetNullValue = {StaticResource的DefaultImage}}/＆GT;
 

由于我们设置了FallbackValue和TargetNullValue作为BitmapImage的的静态资源，
它的工作原理。

I'm trying to set FallbackValue in case when my converter cannot be call, but I'm not sure how to do that.

<Image Source="{Binding FallbackValue="Pictures/Unknown.png", Path=LatestPosition.DeviceFamily, Converter={x:Static conv:ConverterSet.DeviceTypeToImageSourceconverter}}" Name="image1" Stretch="Fill" Margin="5,8" Width="150" Height="150" Grid.RowSpan="4" />

Paths of external images in converter looks like that and when LatestPosition!=null the image is set in proper way.

private static readonly ImageSource Dev1 = new BitmapImage(new Uri("/Pictures/dev1.png", UriKind.Relative));
private static readonly ImageSource Dev2 = new BitmapImage(new Uri("/Pictures/dev2.png", UriKind.Relative));

解决方案

For the Image control, when you Binding the Source property with a URI string, it will automatically convert the URI to a BitmapImage.But if you set the FallbackValue and TargetNullValue as URI string,it will not display.

You need to set it as BitmapImage:

<Window.Resources>
    <BitmapImage x:Key="DefaultImage" UriSource="/Resources;component/Images/Default.jpg" />
</Window.Resources>

<Image Width="128"
               Height="128"
               HorizontalAlignment="Left"
               VerticalAlignment="Top"
               Source="{Binding Photo,FallbackValue={StaticResource DefaultImage},
                                TargetNullValue={StaticResource DefaultImage}}" />

As we set the FallbackValue and the TargetNullValue as StaticResource of BitmapImage,It works.

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