问题描述
谁能给我解释一下下面代码中成员访问中的问号是什么意思?
Can someone please explain to me what does the question mark in the member access in the following code means?
它是标准 C# 的一部分吗?尝试在 Xamarin Studio 中编译此文件时出现解析错误.
Is it part of standard C#? I get parse errors when trying to compile this file in Xamarin Studio.
this.AnalyzerLoadFailed?.Invoke(this, new AnalyzerLoadFailureEventArgs(AnalyzerLoadFailureEventArgs.FailureErrorCode.NoAnalyzers, null, null));
AnalyzerFileReference.cs 行195
推荐答案
Null Propagation operator在C#6中引入,只有对象this.AnalyzerLoadFailed不为null时才会调用该方法:>
It is Null Propagation operator introduced in C# 6, it will call the method only if object this.AnalyzerLoadFailed is not null:
this.AnalyzerLoadFailed?.Invoke(this, new AnalyzerLoadFailureEventArgs(AnalyzerLoadFailureEventArgs.FailureErrorCode.NoAnalyzers, null, null));
等于:
if( this.AnalyzerLoadFailed != null) this.AnalyzerLoadFailed.Invoke(this, new AnalyzerLoadFailureEventArgs(AnalyzerLoadFailureEventArgs.FailureErrorCode.NoAnalyzers, null, null));
参见 C# 6.0 – 空传播运算符,您也可以在此处
我也曾经在 c# 6 中写过这个即将推出的特性 <强>这里
i also once wrote about this upcoming feature in c# 6 here