C# 应该“作为字符串”像这样工作吗？
因为字符串在处理对象数组时给我带来了问题。执行后的值显示在注释中。应该这样工作吗？
object[] array = new object[2];
array[0] = 0.33;
array[1] = "0.33";
string a = array[0] as string; // a == null !!!??????
string b = array[1] as string; // b == "0.33"
string a2 = array[0] == null ? "" : array[0].ToString(); // a2 == "0.33"
string a3 = Convert.ToString(array[0]); // a3 == "0.33"
as string caused me a problem when dealing with object arrays. The values after execution are shown in the comments. Should it work this way?
object[] array = new object[2];
array[0] = 0.33;
array[1] = "0.33";
string a = array[0] as string; // a == null !!!??????
string b = array[1] as string; // b == "0.33"
string a2 = array[0] == null ? "" : array[0].ToString(); // a2 == "0.33"
string a3 = Convert.ToString(array[0]); // a3 == "0.33"
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评论（7）
是的，应该的。
as是强制转换运算符。它只能用于将对象转换为其实际类型（或其超类）。
如果
x不是Y，则x as Y返回null。Yes, it should.
asis a cast operator.It can only be used to cast an object to a type that it actually is (or a superclass thereof).
x as Yreturnsnullifxisn't aY.当 as 运算符无法将对象强制转换为指定类型时，将返回 null。在本例中，它无法将 0.33 转换为字符串类型，因此字符串 a 为空。
the as-operator returns null when it fails to cast an object to the specified type. in this case it failed to cast 0.33 to type string, so string a is null.
MSDN：
所以是的，您观察到的行为是正确的。
MSDN:
So yes, the behaviour you are observing is correct.
as 运算符是强制转换操作，而不是转换操作，因此它只会产生相同类型、超类或子类或您尝试转换为的类型的值。
（与常规转换不同，
as运算符也不使用operator关键字执行用户定义的转换。）The as operator is a casting operation, not a conversion operation, so it will only produce the value is the same type, or a super- or sub-class or the type you are trying to cast to.
(Unlike a regular cast, the
asoperator also does not perform user-defined conversions using theoperatorkeyword.)“as string”不是“ToString()”的同义词。您正在使用“as”运算符，并且碰巧将其字符串作为类型传递。
as 运算符的定义：
备注
as 运算符类似于强制转换，只不过它在转换失败时生成 null，而不是引发异常。更正式地说，表达式的形式为：
表达式作为类型
相当于：
表达式是类型？ （类型）表达式：（类型）null
"as string" is not a synonym for "ToString()". You are using the "as" operator, and happened to pass it string as a type.
Definition of the as operator:
Remarks
The as operator is like a cast except that it yields null on conversion failure instead of raising an exception. More formally, an expression of the form:
expression as type
is equivalent to:
expression is type ? (type)expression : (type)null
“as”运算符基本上类似于转换为 System.Type，但唯一的区别是，如果转换失败，它会返回 null 值，而不是引发异常。
查看此链接以获取更多信息
http://msdn.microsoft.com/en-我们/库/cscsdfbt(v=vs.71).aspx
The 'as' operator is basically like casting into a System.Type however the only difference is that it returns a null value if the cast fails instead of throwing an exception.
Check out this link for more info
http://msdn.microsoft.com/en-us/library/cscsdfbt(v=vs.71).aspx
array[0]是一个double，无法转换为string，因此null。调用
ToString()，大多数类型都会重写它以返回有意义的内容。array[0]is adoubleand cannot be casted tostring, hencenull.Call
ToString(), most types override it to return something meaningful.