将WPF中的图像源绑定到Url [英] Bind Image Source in WPF to a Url

问题描述

我一直浏览不同的帖子，试图弄清楚我的问题是什么问题。基本上我在我的用户控件上有一个Image标签，Source我想绑定到一个url。但是这不行。我尝试使用ValueConverter返回 BitmapImage（new Uri（（string）value））;
但是这不起作用。我唯一能够得到的是你不能绑定到一个url，你必须下载你要绑定的映像。我不想下载所有图像我seacrch。有没有办法解决这个任务，不必在本地下载图像。我认为ValueConverter方法是最好的返回一个BitmapImage。请帮助？

I having been browsing around different posts trying to figure out what is wrong with my issue. Basically I have a Image tag on my user control, and the Source I would like to bind to a url. However this does not work. I have tried using a ValueConverter that returns BitmapImage(new Uri((string)value)); but this does not work. The only thing I have been able to get is that you cannot bind to a url and that you have to download the image you want to bind. I do not want to download all images I seacrch. Is there a work around to achieving this task with out having to download the image locally. I thought the ValueConverter method would have been the best by return a BitmapImage. Please help?

public class MyViewModel
{
    private string _posterUrl;
        public string PosterUrl
        {
            get
            {
                //Get Image Url, this is an example and will be retrieved from somewhere else.
                _posterUrl = "http://www.eurobuzz.org/wp-content/uploads/2012/08/logo.jpg";
                return _posterUrl;    
            }
            set 
            { 
                _posterUrl = value;
                NofityPropertyChanged(p => p.PosterUrl);
            }
        }
}

这是我的ValueConverter： / p>

This is my ValueConverter:

public class BitmapImageConverter : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        if(value is string)
            return new BitmapImage(new Uri((string)value, UriKind.RelativeOrAbsolute));

        if(value is Uri)
            return new BitmapImage((Uri)value);

        throw new NotSupportedException();
    }

    public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
    {
        throw new NotSupportedException();
    }
}

这是我的XAML：

<Image Source="{Binding PosterUrl, Converter={StaticResource bitmapImageConverter}}" Width="100" Height="100" />

所以这是绑定到包含imageurl的PosterUrl属性，并将其转换为位图图像。任何想法？

So this is binding to the PosterUrl property that contains the imageurl and this is converted to a bitmapimage. Any ideas?

推荐答案

尝试

<Image Helpers:ImageAsyncHelper.SourceUri="{Binding Url, IsAsync=True}" x:Name="img" />

其中

using System;
using System.Windows;
using System.Windows.Data;
using System.Windows.Controls;

public class ImageAsyncHelper : DependencyObject {
    public static Uri GetSourceUri(DependencyObject obj){
        return (Uri)obj.GetValue(SourceUriProperty);
    }

    public static void SetSourceUri(DependencyObject obj, Uri value){
        obj.SetValue(SourceUriProperty, value);
    }

    public static readonly DependencyProperty SourceUriProperty =
        DependencyProperty.RegisterAttached("SourceUri",
            typeof(Uri),
            typeof(ImageAsyncHelper),
            new PropertyMetadata { PropertyChangedCallback = (obj, e) =>
                ((Image)obj).SetBinding(
                    Image.SourceProperty,
                    new Binding("VerifiedUri"){
                        Source = new ImageAsyncHelper{
                            _givenUri = (Uri)e.NewValue
                        },
                        IsAsync = true
                    }
                )
            }
        );

    private Uri _givenUri;
    public Uri VerifiedUri {
        get {
            try {
                System.Net.Dns.GetHostEntry(_givenUri.DnsSafeHost);
                return _givenUri;
            }
            catch (Exception) {
                return null;
            }
        }
    }
}

public Uri Url {
    get {
        return new Uri(SomeString, UriKind.Absolute);
    }
}

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