Question

Not exactly how sure how to title this question, so I hope the title works.

The question is, can I use something similar to implicit type syntax on method calls. For example, this is the implicit type syntax I am referring to:

var x = new Y(){Foo = "Bar", Id = 1};

And I want to do something like this:

var x = myInstance.CreateItem(){Foo = "Bar", Id = 1};

Is there anything in C# that supports something like this? I don’t want to do:

x.Foo = "Bar";
x.Id = 1;
...

Please note that CreateItem returns a dynamic type. The CreateItem method and its class cannot be modified.

I would settle for something similar to the With statement in VB.

Thanks in advance.

UPDATE: Attempting Mark Brackett’s solution yielded this code:

TaskItem item = outlook.CreateItem(OlItemType.olTaskItem)._((Action<dynamic>)(i => 
            {
                i.Subject = "New Task";
                i.StartDate = DateTime.Now;
                i.DueDate = DateTime.Now.AddDays(1);
                i.ReminderSet = false;
                i.Categories = "@Work";
                i.Sensitivity = OlSensitivity.olPrivate;
                i.Display = true;

            }));

…

public static class Extension
{
    public static T _<T>(this T o, System.Action<dynamic> initialize) where T : class
    {
        initialize(o);
        return o;
    }

}

The only problem now is that the extension method doesn’t seem to be binding to System._ComObject because I get this error: System._ComObject’ does not contain a definition for ‘_’.

Answer 1

It’s called an “object initializer”, and no – it’s not available for return values (or really, anytime other than with a new statement).

Syntax wise, about the closest I can think of would be to use an Action delegate (which requires changes to the Builder):

MyItem CreateItem(Action<MyItem> afterCreate) {
   var i = new MyItem();
   if (afterCreate != null) afterCreate(i);
   return i;
}

var x = Builder.CreateItem(i => { i.Foo = "Bar"; i.Id = 1; });

If you’re in a JavaScripty mood for short method names for commonly used functions, and can’t change the Builder, I guess an extension method would also work:

public static T _<T>(this T o, Action<T> initialize) where T : class {
    initialize(o);
    return o;
}

var x = Builder.CreateItem()._(i => { i.Foo = "Bar"; i.Id = 1; });

Here’s a twist for you. CreateItem() returns a dynamic type

Contrary to my comment, dynamic does require a few changes. You need to cast to object or the lambda will complain, and then you need to specify dynamic as T or it’ll be inferred as object. Or, create your extension method with Action<dynamic> and no type arguments.

object CreateItem() {
    return (object)Builder.CreateItem();
}

public static dynamic __(this object o, Action<dynamic> initialize) {
    initialize(o);
    return o;
}

var x = CreateItem().__(i => { i.Foo = "Bar"; i.Id = 1; });