Safely Process SPSite.AllWebs

Probably the ugliest scenario for properly disposing SPWeb objects is cleaning up when you enumerate SPSite.AllWebs. To simplify that task, I present a pair of LINQ-inspired extension methods:

public static void ForEach(this SPWebCollection webs, Action<SPWeb> action)
{
    foreach (SPWeb web in webs)
    {
        action(web);
        web.Dispose();
    }
}

public static IEnumerable<TResult> Select<TResult>(this SPWebCollection webs, Func<SPWeb, TResult> action)
{
    List<TResult> res = new List<TResult>(webs.Count);
    webs.ForEach(w => res.Add(action(w)));
    return res;
}

public static IEnumerable<TResult> Select<TResult>(this SPWebCollection webs, Func<SPWeb, TResult> selector)
{
    foreach (SPWeb web in webs)
    {
        TResult ret = selector(web);
        web.Dispose();
        yield return ret;
    }
}

Combined with lambda expressions, we can cleanly handle tasks that would ordinarily require more code and explicit disposal. Want a list of your web URLs?

var urls = site.AllWebs.Select(w => { return w.Url; });

How about updating a property on every web?

site.AllWebs.ForEach(w =>
{
    w.Properties["MyProp"] = DateTime.Now.ToString();
    w.Properties.Update();
});

We can even leverage anonymous types:

var props = site.AllWebs.Select(w =>
{
    return new
    {
        w.Title,
        w.Url,
        MyProp = w.Properties["MyProp"]
    };
});

Speaking of LINQ and SharePoint, check out Adam Buenz‘s post on using LINQ’s IEnumerable.Cast<T> with SharePoint collections to get IQueryable support. And while using LINQ for filtering and such may be prettier, resist the urge to skip CAML altogether: there is definitely a performance advantage in filtering your SPListItemCollection with an SPQuery, especially for large lists. I can’t seem to find any hard data on this, so I nominate Waldek Mastykarz to investigate – his analyses of other performance topics were great.

Update 12/10/2008: New, improved Select! Discussed here.

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