类库无法识别 CommandManager 类 [英] Class library does not recognize CommandManager class

问题描述

我正在开发 WPF 应用程序，我想重用所有这些应用程序中相同的类，以便将它们添加为参考.

I'm developing WPF applications and I want to reuse my classes that are the same in all those applications so I can add them as a reference.

就我而言，我有一个命令类:

In my case I have a class for my Commands:

public class RelayCommand : ICommand
{
    #region Fields

    readonly Action<object> _execute;
    readonly Predicate<object> _canExecute;

    #endregion // Fields

    #region Constructors

    public RelayCommand(Action<object> execute)
        : this(execute, null)
    {

    }

    public RelayCommand(Action<object> execute, Predicate<object> canExecute)
    {
        if (execute == null)
            throw new ArgumentNullException("execute");

        _execute = execute;
        _canExecute = canExecute;
    }
    #endregion // Constructors

    #region ICommand Members

    public bool CanExecute(object parameter)
    {
        return _canExecute == null ? true : _canExecute(parameter);
    }

    public event EventHandler CanExecuteChanged
    {
        add { CommandManager.RequerySuggested += value; }
        remove { CommandManager.RequerySuggested -= value; }
    }

    public void Execute(object parameter)
    {
        _execute(parameter);
    }

    #endregion // ICommand Members
}

这在我的应用程序中完美运行，但是当我想创建一个只想在项目中添加作为参考的类库时，Visual Studio 无法构建，因为CommandManager 没有存在于当前语境中".在我的使用中，我有以下(应该足够了)

This works perfect in my application, but when I want to make a class library which I just want to add as a reference in my project, visual studio can't build because "CommandManager does not exists in the current context". In my usings I have the following (which should be enough)

 using System;
 using System.Windows.Input;

任何想法为什么我不能在类库项目"中这样做?

Any ideas why I can't do this in a "class library project" ?

推荐答案

转到类库的引用"部分并选择添加引用".查找名为PresentationCore"的程序集并添加它.

Go to the "References" part of your class library and select "Add Reference". Look for an assembly called "PresentationCore" and add it.

然后在你的类文件中添加 using 语句 using System.Windows.Input;

Then in your class file add the using statement using System.Windows.Input;

然后您就可以按预期访问 CommandManager.

You will then be able to access the CommandManager as you expect.

只是补充:很多人在创建类库时，他们选择WPF 自定义控件库"，然后删除Class1.cs"文件.这是一个快捷方式，可以自动将正确的命名空间添加到您的库中.捷径是好是坏是任何人的决定，但我一直都在使用它.

Just adding: lots of guys when they go to create a class library, they select "WPF Custom Control Library" and then erase the "Class1.cs" file. It's a shortcut that automatically adds the right namespaces to your library. Whether it's a good or bad shortcut is anybody's call, but I use it all the time.

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