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Seeking an explanation of what "Action" does in this method?

Posted on 2012-03-28
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Last Modified: 2012-03-28
I'm very new to the Action delegate and have no idea what is going on here. Could someone please explain what could be the purpose of putting "Action" here? Is this somehow related to a "pass by reference"?
public void Traverse(Action<Node> v)
{
   v(this);
   foreach (var c in Children) //Children being a property that returns ReadOnlyCollection containing a List<Node>
   {
      c.Traverse(v);
   }
}

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Question by:Eindoofus
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käµfm³d   👽 earned 500 total points
ID: 37779930
Action is a type, and it can be thought of like a pointer to a function that has no return value (i.e. returns void). The counterpart to Action for functions which do return values is Func.

Action is delegate type. You can execute an instance of a delegate as if it were an actual function (this is what line 3 in your snippet is doing).

The net effect of your code is that you can pass in the name of any function (within scope) that accepts a parameter of type Node and which returns nothing. Inside of Traverse, this function will be executed at line 3, passing the reference to the current class (which is assumed be Node) to the target function as its parameter.
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by:Eindoofus
ID: 37779974
Thanks. Btw, can this be considered a recursive method?
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by:käµfm³d 👽
ID: 37779987
Yes, because it calls itself (line 6).

Also, I just saw the part of your question regarding "pass-by-reference". Action is a class, so it would be pass-by-reference. All classes are passed by reference. Value types (including structs) are passed by value.
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