c# – 将WPF中的图像源绑定到URL

我一直在浏览不同的帖子,试图弄清楚我的问题有什么问题.基本上我的用户控件上有一个 Image标签,而我想要绑定到一个url.但是这不起作用.我尝试使用返回BitmapImage的ValueConverter(new Uri((string)value));
但这不起作用.我唯一能得到的是你不能绑定到一个url,你必须下载你想要绑定的图像.我不想下载我seacrch的所有图像.是否需要在本地下载图像来完成此任务.我认为通过返回BitmapImage,ValueConverter方法将是最好的.请帮忙？

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：

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,CultureInfo culture)
    {
        throw new NotSupportedException();
    }
}

这是我的XAML：

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

因此,它绑定到包含imageurl的PosterUrl属性,并将其转换为bitmapimage.有任何想法吗？

解决方法

试试吧

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

哪里

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;
            }
        }
    }
}

和

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