What does the question mark in member access mean

Question

Can someone please explain to me what does the question mark in the member access in the following code means?

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 line 195

Answer 1

In C# version 6 it will be shorthand for

if (this.AnalyzerLoadFailed != null)
    this.AnalyzerLoadFailed.Invoke(this, new AnalyzerLoadFailureEventArgs(AnalyzerLoadFailureEventArgs.FailureErrorCode.NoAnalyzers, null, null));

Answer 2

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));

is equal to :

if( this.AnalyzerLoadFailed != null)
    this.AnalyzerLoadFailed.Invoke(this, new AnalyzerLoadFailureEventArgs(AnalyzerLoadFailureEventArgs.FailureErrorCode.NoAnalyzers, null, null));

See C# 6.0 – Null Propagation Operator , also you can see here

i also once wrote about this upcoming feature in c# 6 here