How to put a lambda with external parameters into a callback function

Question

I have the following code which basically does what I want:

string firstName = "Chuck";
string lastName = "Norris";

 filtered = dvds.Where(
            dvd => (dvd.Element("Actors") != null) && (dvd.Element("Actors").Elements("Actor").Where(
                actor => actor.Attribute("FirstName") != null && actor.Attribute("FirstName").Value == firstName 
                    && actor.Attribute("LastName") != null && actor.Attribute("LastName").Value == lastName)).Count() > 0);

As you can see, the lambda is quite big. I'd rather have a callback method in the first .Where call. But I don't see how I could give the firstName and lastName parameters into that callback method.

Is that even possible?

Thomas Levesque · Accepted Answer · 2013-06-02 19:33:40Z

1

You can't just pass a method to the first Where, since you also need to pass the first and last names, but you can pass a simpler lambda... Here's a possible refactoring:

filtered = dvds.Where(dvd => HasActor(dvd, firstName, lastName));
...

bool HasActor(XElement dvd, string firstName, string lastName)
{
    var actors = dvd.Element("Actors");
    if (actors != null)
    [
        var actor = actor.FirstOrDefault(a => IsActor(a, firstName, lastName));
        return actor != null;
    }
    return false;
}

bool IsActor(XElement actor, string firstName, string lastName)
{
    string firstNameAttr = actor.Attribute("FirstName");
    string lastNameAttr = actor.Attribute("LastName");
    return firstNameAttr != null
        && firstNameAttr.Value == firstName
        && lastNameAttr != null
        && lastNameAttr.Value == lastName;
}

answered Jun 2, 2013 at 19:33

Thomas Levesque

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1 Comment

Dee J. Doena Over a year ago

slaps head Sometimes you don't see the forest for the trees. Of course(!) I can just call another method and pass on the additional parameters. Now I feel stupid. :-/

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