C# 三元运算符如何工作？
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How does the ternary operator work?
提问by Sara S
Please demonstrate how the ternary operator works with a regular if/else block. Example:
请演示三元运算符如何与常规 if/else 块配合使用。例子：
Boolean isValueBig = value > 100 ? true : false;
Exact Duplicate:How do I use the ternary operator?
完全重复：如何使用三元运算符？
采纳答案by Kent Fredric
Boolean isValueBig = ( value > 100 ) ? true : false;
Boolean isValueBig;
if( value > 100 ) {
isValueBig = true;
} else {
isValueBig = false;
}
回答by Sampson
PHP Example
PHP 示例
<?php
// Example usage for: Ternary Operator
$action = (empty($_POST['action'])) ? 'default' : $_POST['action'];
// The above is identical to this if/else statement
if (empty($_POST['action'])) {
$action = 'default';
} else {
$action = $_POST['action'];
}
?>
"The expression (expr1) ? (expr2) : (expr3)evaluates to expr2if expr1evaluates to TRUE, and expr3if expr1evaluates to FALSE."
“表达（表达式1）（表达式2）：（表达式3）的计算结果为表达式2如果expr1的计算结果为TRUE，并且表达式3如果表达式1计算结果为FALSE”。
回答by user54650
Boolean isValueBig;
if(value > 100) { isValueBig = true; } else { isValueBig = false; }
回答by empi
Boolean isValueBig;
if (value > 100)
{
isValueBig = true;
}
else
{
isValueBig = false;
}
回答by Konrad Rudolph
When I was new to C++, I found that it helped to read this construct as follows:
当我刚接触 C++ 时，我发现它有助于阅读以下构造：
Boolean isValueBig = if condition ? then x else: y;
(Notice that this isn't valid code. It's just what I trained myself to read in my head.)
（请注意，这不是有效代码。这只是我训练自己在脑海中阅读的内容。）
回答by Dan Monego
The difference between the ternary operation and if/else is that the ternary expression is a statement that evaluates to a value, while if/else is not.
三元运算与 if/else 的区别在于，三元表达式是求值结果的语句，而 if/else 则不是。
To use your example, changing from the use of a ternary expression to if/else you could use this statement:
要使用您的示例，从使用三元表达式更改为 if/else 您可以使用以下语句：
Boolean isValueBig = null;
if(value > 100)
{
isValueBig = true
}
else
{
isValueBig = false;
}
In this case, though, your statement is equivalent to this:
但是，在这种情况下，您的语句等效于：
Boolean isValueBig = (value > 100);
回答by Craig
As quoted from the ?: Operator MSDN page, "the conditional operator (?:) returns one of two values depending on the value of a Boolean expression."
正如引用自?: Operator MSDN page，“条件运算符 (?:) 根据布尔表达式的值返回两个值之一。”
So you can use the ternary operator to return more than just booleans:
因此，您可以使用三元运算符返回的不仅仅是布尔值：
string result = (value > 100 ) ? "value is big" : "value is small";
回答by billb
I was never a fan of the ternary operator because I thought it was hard to read. As it so happens, Jon Skeet and his book, C# in Depthfinally hit this old dog over the head and got it to sink in. Jon said, and I paraphrase, think of it as a question.
我从来不是三元运算符的粉丝，因为我认为它很难阅读。碰巧的是，Jon Skeet 和他的书，C# in Depth最终击中了这只老狗的头，让它沉入其中。Jon 说，我解释说，把它当作一个问题。
value > 100?
"yes" : "no"
值 > 100？
“是”：“否”
Now the blind can see.
现在盲人可以看见了。
Hope this helps you make it second nature.
希望这可以帮助您使其成为第二天性。
回答by Brian Rudolph
Bad example, because you could easily write
不好的例子，因为你可以很容易地写
Boolean isValueBig = value > 100 ? true : false;
as:
作为：
bool isValueBig = value > 100
Beyond that, everyone else has already answered it. I would just not recommend using ternary operators to set bool values, since what you are evaluating is already a boolean value.
除此之外，其他人都已经回答了。我只是不建议使用三元运算符来设置 bool 值，因为您正在评估的已经是一个布尔值。
I realize it was just an example, but it was worth pointing out.
我意识到这只是一个例子，但值得指出。
回答by Peter ?tibrany
Make sure you don't mix types in true/false parts in Java. It produces weird results :-(
确保不要在 Java 中的真/假部分混合类型。它产生奇怪的结果:-(
