Is there any Null-Conditional Operator like for Events.. Button?.Click +=(ss,ee)

Question

Why there's no Null-Conditional Operator for events ?

For example i have following code which raise event if object is not null :

Button TargetButton =  null;

    if(IsRunning)
    {
       TargetButton = new ....
    }

TargetButton?.Click +=(ss,ee)=>{...}

// Compile-time error 
// The event 'EditorButton.Click' can only appear on the left hand side of += or -= 

briefly :

is there alternative ? than using usual if(TargetButton != null ) ... raise event

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Answer 1

The problem is not related to events.

The null-conditional operator is to stop an evaluation if a reference is null.

It is not applicable in the left or right part of an assignment.

If you have:

public class Test
{
  public int Value;
  public void Method() { }
}

You can't write:

Test v;

v?.Value = 10;

int a = v?.Value;

Because if v is null, v.Value is not evaluated.

• So what to do with = 10 ?

• Or what to do with a ?

Thus it is the same when adding or removing an event handler to an event variable that is null when empty.

C# event is null

Hence the compiler error to disallow such writings.

It is why you can't write:

TargetButton?.Click +=(ss,ee)=>{...}

Because what to to with (ss,ee)=>{...} if TargetButton is null?

You can say that you want the compiler ignores that.

But the compiler disallows doing such unclean thing.

What we can write is:

v?.Test();

Here is v is null the method is not called and all is fine because there is nothing right or left that the compiler does not know what to do with.

int a = v?.Value ?? 0;

Here if v is null 0 is used.

Null-conditional operators ?. and ?[]

Null-coalescing operators ?? and ??=