C# 问号运算符后缀进行强制转换
我正在查看 dapper 页面，看到了这段简短的编码：
new { Age = (int?)null, Id = guid });
什么(int?)null 可以吗？
有人可以解释一下那里发生了什么，也许可以给出更“详细”的代码版本吗？
I was looking at the dapper page and saw this terse bit of coding:
new { Age = (int?)null, Id = guid });
What does (int?)null do?
Could someone please elucidate what is going on there, and perhaps give a more "verbose" version of the code?
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int?是Nullable的简写。因此，这行代码将 null （默认情况下为object类型）转换为 null int。文档：http://msdn.microsoft.com/en-us/library/b3h38hb0.aspx
int?is shorthand forNullable<int>. as such this line of code is converting null (which by default is of typeobject) to a null int.Docs: http://msdn.microsoft.com/en-us/library/b3h38hb0.aspx
如果您拥有的只是
new { Age = null }，编译器无法知道Age的确切类型是什么。因此，将null转换为Nullable有效地告诉它Age属性属于该类型。If all you have is
new { Age = null }, compiler has no way of knowing what is the exact type ofAge. So "casting"nulltoNullable<Int32>effectively tells it thatAgeproperty is of that type.这是一个匿名类型：
年龄 必须从分配给它的值中隐含。null可以是任何可为空的类型。强制转换指定Age应具有的类型：int?（又名Nullable）This is an anonymous type: The type of
Agemust be implied from the value assigned to it.nullcan be any nullable type. The cast specify the type thatAgeshould have:int?(akaNullable<int>)?标记 < code>Nullable int它是
((System.Nullable)null) 的语法简写。?marks aNullableintIt is a syntactical shorhand for
((System.Nullable<int>)null).