Question

I want to chain together two (and possibly more in the future) methods to a delegate and just wondered if there is a way to do this in one assignment statement, e.g.

I have a delegate method signature defined as

public delegate void MaskRequestSection(Request request); 

…and 2 methods that use this signature, namely…

public void MaskCvnSection(Request request)
{
    // do the masking operation
}

public void MaskCardNumberSection(Request request)
{
    // do the masking operation
}

At present, I am using the following to instantiate the delegete, chain the 2 methods to it and then invoke them…

private void HideDetailsInRequest(Request request)
{
    MaskRequestSection maskRequestSection = MaskCvnSection;
    maskRequestSection += MaskCardNumberSection;
    maskRequestSection(request);
}

….I am just curious as to why I can’t chain both delegates in one statement like below,

MaskRequestSection maskRequestSection = MaskCardNumberSection+ MaskCvnSection;

…but also if there is another way that it can be done within one declaration. I haven’t been able to find anything that specifically addresses this on MSDN, and I’m just asking for my own curiosity.

Thanks in advance.

Answer 1

You can do it with a cast:

var maskRequestSection = (MaskRequestSection) MaskCardNumberSection
       + (MaskRequestSection) MaskCvnSection;

… but you can’t do it without one, because the + operator here works on delegates, not method groups. When the compiler sees the binary + operator, it has to work out the type of the expression, and that doesn’t take the assignment part into account.