如何从C# 8 switch表达式返回到一个属性和两个本地声明的变量？

Question

我有一个运行良好的代码：

        var (msg, isCC, upd) = Settings.Mode switch
        {
            MO.Learn => ("Use this mode when you are first learning the phrases and their meanings.",
                                Settings.Cc == CC.H,
                                false),
            MO.Practice => ("Use this mode to help you memorize the phrases and their meanings.",
                                Settings.Cc == CC.H,
                                false),
            MO.Quiz => ("Use this mode to run a self marked test.",
                                Settings.Cc == CC.H,
                                true),
            _ => ("", false, false)
        };

但在实际的应用程序中，我想将一个值返回到一个属性中，该属性在这里的多个位置被赋值：

    string _modeMessage2;
    public string ModeMessage2 { get => _modeMessage2; set => SetProperty(ref _modeMessage2, value); }

尝试这样做不起作用：

        var (this.ModeMessage2, isCC, upd) = Settings.Mode switch
        {
            MO.Learn => ("Use this mode when you are first learning the phrases and their meanings.",
                                Settings.Cc == CC.H,
                                false),
            MO.Practice => ("Use this mode to help you memorize the phrases and their meanings.",
                                Settings.Cc == CC.H,
                                false),
            MO.Quiz => ("Use this mode to run a self marked test.",
                                Settings.Cc == CC.H,
                                true),
            _ => ("", false, false)
        };

有谁知道如何在不添加如下代码的情况下将值返回到ModeMesage2中？

ModeMessage2 = msg; 

Answer 1

如果左边的所有项都是字段或属性，那么它将起作用，如果您随后尝试将其中一项更改为类似var isCC的表达式，则会得到一个编译器错误，说明您不能混合表达式和声明。

因此，不幸的是，这不受支持。