.net - VB.Net 中的 WPF 标记扩展不起作用

Question

我正在尝试根据 this blog post 创建一个 VB.Net 标记扩展但是在 vb.net 中

<Application x:Class="Application"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    ShutdownMode="OnExplicitShutdown">
    <Application.Resources>        
    </Application.Resources>
    <JumpList.JumpList>
        <JumpList ShowRecentCategory="True">
            <JumpTask Title="Save as..." Arguments="-saveas"
                      ApplicationPath="{local:ApplicationFullPath}">
            </JumpTask>
        </JumpList>
    </JumpList.JumpList>
</Application>

但它正在 throw

Error 1 Unknown build error, 'Key cannot be null. Parameter name: key Line 9 Position 62.' C:\Users\jessed.ECREATIVE\My Dropbox\Projects\c2d2\c2d2\Application.xaml 9 62 c2d2

我将示例的 c# 部分转换为

Public Class ApplicationFullPath
    Inherits Markup.MarkupExtension

    Public Overrides Function ProvideValue(ByVal serviceProvider As System.IServiceProvider) As Object
        Return System.Reflection.Assembly.GetExecutingAssembly.Location()
    End Function

End Class

我错过了什么吗？任何帮助将不胜感激

Answer 1

说真的，我绝不会为此使用标记扩展。

不如这样:

public partial class App : Application
{
    public static string ApplicationFullPath
    {
        get { return Assembly.GetExecutingAssembly().Location; }
    }

    ...

<JumpTask ApplicationPath="{x:Static local:App.ApplicationFullPath}"/>

(标记扩展类名称应该以“Extension”结尾，也许这甚至可以解决您的问题(该类将被称为 ApplicationFullPathExtension ， XAML 中的调用仍将是 ApplicationFullPath though))