I really think that either SPBaseCollection (from which SPWebCollection,SPFolderFollection and SPFileCollection) included a Contains feature.  Preferably a containsKey feature.

This article will present a method for quickly establishing if any of the
3 classes contain an object with a specific name.

First some background:

SPBaseCollection derives from ICollection, which unfortunately does not contain a definition for Contains.  The new ICollection<T> generic interface does contain a definition for it though. so Microsoft did learn.

SPBaseCollection is the base class for almost all the Sharepoint collections (a list is here), and a contains method that is based on the name, such as the indexers in SPFolder,SPFile and SPWeb collection might not lend itself to all of them.   A second base class that classes that shared a string indexer would be beneficial.

If I was working on a project with C# 3.0 I could have used the new feature of extension methods to inject a contains into the collections I work with, but since I am stuck with C# 2.0 that wont work.

I have seen a lot of code, and even written some code for Sharepoint that looks through the entire collection for a specific entry.

In fact if Sharepoint had been upgraded with 3.0 and Linq, I could perhaps write Linq queries to access the objects I wanted.

Instead of this:

     foreach (SPList list in web.Lists)
                {

                   if (list.BaseType == SPBaseType.DocumentLibrary)
                    {
                        lists.Add(list);
                    }
                }

Linq could rescue me.

The goal for this article though is much simpler. I don't wish to have to iterate over SPWebCollection with a foreach looking for a specific site by name.

SPWebCollection does have an indexer that takes a string, that contains the name, but not a lookup like Contains.

 I had expected that the indexer would throw an exception if I queried it with a non existent site.  I didn't wish to incur the cost of an exception.

Testing however shows that SPFolderCollection,SPFileCollection and SPWebCollection all implement the string indexer and none of them throw an exception if queried with a non existent name.

Instead they return a an object of the type that the collection represents, but the collections property .Exists is set to false. Its basically an empty object.

This allows a syntax such as collection[name].Exists to be used, and it will not throw a nullException.

I created the following set of functions, because I like the explicit syntax of the methods, but its certainly less verbose to just invoke the Exists directly .

public static bool doesSPWebCollectionContainName(SPWebCollection collection, string name)
        {
            return collection[name].Exists;
        }

public static bool doesSPFileCollectionContainName(SPFileCollection collection, string name)
        {
            return collection[name].Exists;
        }

public static bool doesSPFolderCollectionContainName(SPFolderCollection collection, string name)
        {
            return collection[name].Exists;
        }

Either way it is certainly better than iterating over the collection looking for a specific entry.

UPDATE:

It seems that even though everything should run fine according to the API, when it comes to SPFile and SPFolder they function in a different manner than expected as compared to SPWeb.

Ufortunatly SPFileCollection and SPFolderCollection seems to throw an Exception when the indexer tries to access a non existing entity. SPWeb doesnt.  These work, but it involves the much dreaded Exception.

 public static bool doesSPFileCollectionContainName(SPFileCollection collection, string name)
        {
            try
            {
                return collection[name].Exists;
            }
            catch (Exception )
            {
                return false;
            }
        }

        public static bool doesSPFolderCollectionContainName(SPFolderCollection collection, string name)
        {
            try
            {
                return collection[name].Exists;
            }
            catch (Exception )
            {
                return false;
            }
        }