C#•5mo ago

Syntax: Using a delegate with simplified collection declaration

Working with Avalonia framework, attempting to use simplified collection declaration, however it does not seem to support setting up events that way. Is there a workaround? It would be a significant help in preventing menu/item declaration from becoming a spaghetti.

a.Menu =
[
    new NativeMenuItem("Top Menu")
    {
        Menu =
        [
            new NativeMenuItem("Nested Item")
            {
                Click += delegate { } 
            }
        ]
    }
];

a.Menu =
[
    new NativeMenuItem("Top Menu")
    {
        Menu =
        [
            new NativeMenuItem("Nested Item")
            {
                Click += delegate { } 
            }
        ]
    }
];

11 Replies

333fred•5mo ago

Are you trying to add to an existing collection, or create a new collection? Also, the cognitive dissonance of using collection expressions and delegate {} syntax in the same code example hurts me

Mtax•5mo ago

a.Menu exists, everything else is new.

333fred•5mo ago

So are you trying to add to Menu, or create a new collection?

Mtax•5mo ago

The Menu I need to add the delegate in is null by default, so I need to create it.

333fred•5mo ago

Alright, so what's the error you're actually getting?

Mtax•5mo ago

If I go with Click +=, I get Invalid initializer member declarator, if I use Click = it forces me to use += on left hand side.

333fred•5mo ago

I'm afraid that doesn't make much sense to me += is indeed not a thing you can do in an object initializer I don't know what the "on the left hand side" you mentioned there is

Mtax•5mo ago

https://learn.microsoft.com/en-us/dotnet/csharp/misc/cs0079?f1url=%3FappId%3Droslyn%26k%3Dk(CS0079)

Compiler Error CS0079 - C#

Compiler Error CS0079

333fred•5mo ago

In all likelyhood, what you need to do is this:

var nestedItem = new NativeMenuItem("Nested Item");
nestedItem.Click += delegate { };

a.Menu =
[
    new NativeMenuItem("Top Menu")
    {
        Menu = [nestedItem]
    }
];

var nestedItem = new NativeMenuItem("Nested Item");
nestedItem.Click += delegate { };

a.Menu =
[
    new NativeMenuItem("Top Menu")
    {
        Menu = [nestedItem]
    }
];

Mtax•5mo ago

Yeah, that is what I figured. Unfortunate, because I could have a visual hierarchy to the menu, otherwise it's mostly going to be named declarations, which get really messy to read with like 20 entries. Regardless, thanks for confirming there is no other way. I appreciate it.

333fred•5mo ago

There is a proposal for supporting it: https://github.com/dotnet/csharplang/issues/5176

GitHub

[Proposal]: Compound assignment in object initializer and with ex...

Compound assignment in object initializer and with expression Proposed Prototype: Not Started Implementation: Not Started Specification: Not Started Summary Allow compound assignments like so in an...

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Syntax: Using a delegate with simplified collection declaration