C# 检查可空布尔值是否为空
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checking if a nullable bool is null or not
提问by Amin Ziaei
Possible Duplicate:
Which is preferred: Nullable<>.HasValue or Nullable<> == null?
I know questions like this have been asked many times. But I never found an answer to how to check if a nullable bool is null or not. Here is an answer I have to this:
我知道这样的问题已经被问过很多次了。但我从未找到如何检查可空 bool 是否为空的答案。这是我对此的回答：
bool? nullableBool;
if (nullableBool == true){
}else if (nullableBool == false){
}else{
}
But I was wondering if there is a better and more straight to the point way in order to minimize useless codes? Thanks.
但我想知道是否有更好更直接的方式来减少无用代码？谢谢。
采纳答案by tukaef
if (!nullableBool.HasValue)
{
// null
}
You also can directly compare it with null.
您也可以直接将其与null.
Edit:
编辑：
Your declaration of nullableBoolshould be:
您的声明nullableBool应该是：
bool? nullableBool;
回答by bonCodigo
Try this plz:
试试这个：
if (!nullableBool.HasValue)
{
// your code
}
回答by Rawling
That's not a nullable bool, it's an unassigned booland your code won't compile. You need to use bool?or Nullable<bool>.
那不是可空的bool，它是未分配的bool，您的代码将无法编译。您需要使用bool?或Nullable<bool>。
bool? nullableBool = null; // or = true or = false
if (nullableBool.HasValue)
{
if (nullableBool.Value)
// true
else
// false
}
else
// null
回答by musefan
Firstly, the bool you have used is not nullable. To create a nullable bool you can do one fo the following:
首先，您使用的 bool 不可为空。要创建可为空的 bool，您可以执行以下操作之一：
Nullable<bool> nullableBool;
or the shorthand version:
或速记版本：
bool? nullableBool;
either of these can then be checked to see if it has a value using the following:
然后可以使用以下方法检查它们中的任何一个以查看它是否具有值：
if(nullableBool.HasValue)
{
//nullableBool has been assigned a value
}
Your current approach is not recommended. If you need a nullable state then use a nullable bool. If you want to use a standard bool then be sure to assign it a value. I am surprised you don't get a compile error in Visual Studio with that code.
不推荐您当前的方法。如果您需要可空状态，则使用可空布尔值。如果您想使用标准布尔值，请务必为其分配一个值。我很惊讶您没有在 Visual Studio 中使用该代码收到编译错误。
