在 C# switch 表达式中使用块？

Question

我找不到解决此问题的文档。（也许我只是不擅长使用 google...）我的猜测是答案是否定的，但是我不明白文档中在哪里解决了这个问题。准确地说，我的问题如下。

假设，我想执行这样的操作：

DirectoryInfo someDir = new DirectoryInfo(@".\someDir");
Console.WriteLine($"Would you like to delete the directory {someDir.FullName}?");
string response = Console.ReadLine().ToLower();

response switch
{
    "yes" => { someDir.Delete(); ... MoreActions},
     _ => DoNothing()
};

我知道我可以通过使用常规 switch 或 if/else 来实现所需的行为，但是我很好奇在这种情况下是否可以使用 switch 表达式。

Answer 1

however I didn't understand where this is addressed in the documentation

这个说的很清楚了here:

There are several syntax improvements here:

The variable comes before the switch keyword. The different order makes it visually easy to distinguish the switch expression from the switch statement.

The case and : elements are replaced with =>. It's more concise and intuitive.

The default case is replaced with a _ discard.

The bodies are expressions, not statements.

{ someDir.Delete(); ... MoreActions} 不是表达式。

但是，您可以滥用每个功能，正如他们所说:)

您可以使 switch 表达式的计算结果为 Action，并调用该操作：

Action a = response switch
{
    "yes" => () => { ... },
     _ => () => { .... }
};
a();

您甚至可以将其简化为一条语句：

(response switch
{
    "yes" => (Action)(() => { ... }),
     _ => () => { ... }
})();

但不要这样做...

Answer 2

As per documentation: 正文是表达式，不是语句。

不过你可以这样做：

Action fn = response switch
{
    "yes" => () => { BlockTest(); },
     _ => () => { OldTest(); }
};

Answer 3

您还可以引入 local function（C# 7.0 及更高版本）并执行以下操作：

response switch
{
    "yes" => DoSomething(),
     _ => DoNothing()
};

void DoSomething()
{
    someDir.Delete();
    ... MoreActions
}

Answer 4

我想这个功能很快就会出现。 Proposal for this

在 C# switch 表达式中使用块？

Using blocks in C# switch expression?

c#

c#-8.0

switch-expression