TryParse没有var参数 [英] TryParse with out var param

问题描述

C＃6.0中的一项新功能允许在TryParse方法内声明变量。
我有一些代码：

A new feature in C# 6.0 allows to declare variable inside TryParse method. I have some code:

string s = "Hello";

if (int.TryParse(s, out var result))
{

}

但是我收到编译错误：

But I receive compile errors:

我做错了什么？
PS：在项目设置中设置了C＃6.0和.NET Framework 4.6。

What I am doing wrong? P.S.: in project settings C# 6.0 and .NET framework 4.6 are set.

推荐答案

C＃6.0中的一项新功能允许在TryParse
方法内声明变量。

A new feature in C# 6.0 allows to declare variable inside TryParse method.

声明表达式是从C＃6.0和尚未在最终版本中发布。您目前无法这样做。 在GitHub上有针对C＃7的建议（另请参见此供以后参考）。

Declaration expressions was cut from C# 6.0 and wasn't shipped in the final release. You currently can't do that. There is a proposal for it on GitHub for C# 7 (also see this for future reference).

随着C＃7的正式发布，将编译以下代码：

With the official release of C#7, the following code compiles:

string s = "42";

if (int.TryParse(s, out var result))
{
     Console.WriteLine(result);
}

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