如何转换C＃可空INT为int [英] How to convert C# nullable int to int

问题描述

我要如何转换成一个可空 INT 到 INT ？假设我有2 int类型如下的：

How do I convert a nullable int to an int? Suppose I have 2 type of int as below:

int? v1;  
int v2; 

我要分配 V1 的价值 V2 。 V2 = V1; 将导致错误。如何转换 V1 到 V2 ？

I want to assign v1's value to v2. v2 = v1; will cause an error. How do I convert v1 to v2?

推荐答案

其他答案为止是正确的;我只是想增加一个这是稍微干净：

The other answers so far are all correct; I just wanted to add one more that's slightly cleaner:

v2 = v1 ?? default(int);

任何可空＆LT; T＆GT; 隐式转换为它的 T ，只要全程前pression正在评估不能得到空值赋值给一个值类型。因此，空合并运算符 ?? 是三元操作只是语法糖：

Any Nullable<T> is implicitly convertible to its T, PROVIDED that the entire expression being evaluated can never result in a null assignment to a ValueType. So, the null-coalescing operator ?? is just syntax sugar for the ternary operator:

v2 = v1 == null ? default(int) : v1;

...而这又是语法糖的的if / else：

...which is in turn syntax sugar for an if/else:

if(v1==null)
   v2 = default(int);
else
   v2 = v1;

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另外，由于.NET 4.0，可空＆LT; T＆GT; 有一个GetValueOrDefault（）方法，这是基本上执行的空值空安全的吸上述合并显示，所以这个工程太：

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Also, as of .NET 4.0, Nullable<T> has a "GetValueOrDefault()" method, which is a null-safe getter that basically performs the null-coalescing shown above, so this works too:

v2 = v1.GetValueOrDefault();

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