如何避免在我的 ViewModel 中查看特定代码 [英] How to avoid View specific code in my ViewModel

问题描述

我的应用程序有一个允许创建新帐户的菜单选项.菜单选项的命令绑定到我的 ViewModel 中的命令 (NewAccountCommand).当用户单击创建新帐户的选项时，应用程序会显示一个新帐户"对话框，用户可以在其中输入姓名、地址等数据...然后单击确定"关闭对话框并创建新帐户.

My application has a menu option to allow the creation of a new account. The menu option's command is bound to a command (NewAccountCommand) in my ViewModel. When the user clicks the option to create a new account, the app displays a "New Account" dialog where the user can enter such data as Name, Address, etc... and then clicks "Ok" to close the dialog and create the new account.

我知道我在 ViewModel 中的代码不正确，因为它创建了新帐户"对话框并调用了 ShowDialog().这是 VM 的一个片段:

I know my code in the ViewModel is not correct because it creates the "New Account" dialog and calls ShowDialog(). Here is a snippet from the VM:

 var modelResult = newAccountDialog.ShowDialog();
 if (modelResult == true)
 {
   //Create the new account             
 }

如何避免在我的 VM 中创建和显示对话框，以便我可以对 VM 进行单元测试?

how do i avoid creating and showing the dialog from within my VM so I can unit test the VM?

推荐答案

在这种情况下，我通常使用事件.该模型可以引发一个事件来询问信息，任何人都可以响应它.视图会监听事件并显示对话框.

In scenarios like this, I typically use events. The model can raise an event to ask for information and anybody can respond to it. The view would listen for the event and display the dialog.

public class MyModel
{
    public void DoSomething()
    {
        var e = new SomeQuestionEventArgs();
        OnSomeQuestion(e);
        if (e.Handled)
            mTheAnswer = e.TheAnswer;
    }
    private string mTheAnswer;
    public string TheAnswer
    {
        get { return mTheAnswer; }
    }
    public delegate void SomeQuestionHandler(object sender, SomeQuestionEventArgs e);
    public event SomeQuestionHandler SomeQuestion;
    protected virtual void OnSomeQuestion(SomeQuestionEventArgs e)
    {
        if (SomeQuestion == null) return;
        SomeQuestion(this, e);
    }
}
public class SomeQuestionEventArgs
    : EventArgs
{
    private bool mHandled = false;
    public bool Handled
    {
        get { return mHandled; }
        set { mHandled = value; }
    }
    private string mTheAnswer;
    public string TheAnswer
    {
        get { return mTheAnswer; }
        set { mTheAnswer = value; }
    }
}
public class MyView
{
    private MyModel mModel;
    public MyModel Model
    {
        get { return mModel; }
        set
        {
            if (mModel != null)
                mModel.SomeQuestion -= new MyModel.SomeQuestionHandler(mModel_SomeQuestion);
            mModel = value;
            if (mModel != null)
                mModel.SomeQuestion += new MyModel.SomeQuestionHandler(mModel_SomeQuestion);
        }
    }
    void mModel_SomeQuestion(object sender, SomeQuestionEventArgs e)
    {
        var dlg = new MyDlg();
        if (dlg.ShowDialog() != DialogResult.OK) return;
        e.Handled = true;
        e.TheAnswer = dlg.TheAnswer;
    }
}

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