如何在一个const字符串中包含枚举值？ [英] How to include an enum value in a const string?

问题描述

从这个问题，我知道一个 const string 可以是 const 的连接。现在，枚举只是一组连续整数，不是吗？
那么为什么不这样做：

from this question, I know that a const string can be the concatenation of const things. Now, an enum is just a set of cont integers, isn't it ? So why isn't it ok to do this :

const string blah = "blah " + MyEnum.Value1;

或此：

const string bloh = "bloh " + (int)MyEnum.Value1;

您将如何在一个const字符串中包含枚举值？

And how would you include an enum value in a const string ?

现实生活中的例子：构建SQL查询时，我想要where status<>+ StatusEnum.Discarded p>

Real life example : when building an SQL query, I would like to have "where status <> " + StatusEnum.Discarded.

推荐答案

作为一个解决方法，您可以使用字段初始化器而不是const，即

As a workaround, you can use a field initializer instead of a const, i.e.

static readonly string blah = "blah " + MyEnum.Value1;

static readonly string bloh = "bloh " + (int)MyEnum.Value1;

至于为什么：对于枚举案例，枚举格式实际上很漂亮复杂，特别是对于 [Flags] case，所以把它留给运行时是有意义的。对于 int 案例，这仍然可能会受文化特定问题的影响，因此再次需要延迟到运行时。编译器实际生成的是一个框操作，即使用 string.Concat（object，object） overload ，相同：

As for why: for the enum case, enum formatting is actually pretty complex, especially for the [Flags] case, so it makes sense to leave this to the runtime. For the int case, this could still potentially be affected by culture specific issues, so again: needs to be deferred until runtime. What the compiler actually generates is a box operation here, i.e. using the string.Concat(object,object) overload, identical to:

static readonly string blah = string.Concat("blah ", MyEnum.Value1);
static readonly string bloh = string.Concat("bloh ", (int)MyEnum.Value1);

其中 string.Concat 将执行的ToString（）。因此，可以认为以下是稍微有效的（避免一个框和一个虚拟调用）：

where string.Concat will perform the .ToString(). As such, it could be argued that the following is slightly more efficient (avoids a box and a virtual call):

static readonly string blah = "blah " + MyEnum.Value1.ToString();
static readonly string bloh = "bloh " + ((int)MyEnum.Value1).ToString();

它将使用 string.Concat（string，string）。

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