String.IsNullOrEmpty is a commonly used method for determining whether a string is null or has a zero length.
But, no such method exists in the FCL for collections. A moment ago I whipped up an extension method for IEnumerable types. It’s not rocket science, but I thought I would post it anyway.
public static class Extensions
{
/// <summary>
/// Determines whether the collection is null or contains no elements.
/// </summary>
/// <typeparam name="T">The IEnumerable type.</typeparam>
/// <param name="enumerable">The enumerable, which may be null or empty.</param>
/// <returns>
/// <c>true</c> if the IEnumerable is null or empty; otherwise, <c>false</c>.
/// </returns>
public static bool IsNullOrEmpty<T>(this IEnumerable<T> enumerable)
{
if (enumerable == null)
{
return true;
}
/* If this is a list, use the Count property.
* The Count property is O(1) while IEnumerable.Count() is O(N). */
var collection = enumerable as ICollection<T>;
if (collection != null)
{
return collection.Count < 1;
}
return !enumerable.Any();
}
/// <summary>
/// Determines whether the collection is null or contains no elements.
/// </summary>
/// <typeparam name="T">The IEnumerable type.</typeparam>
/// <param name="collection">The collection, which may be null or empty.</param>
/// <returns>
/// <c>true</c> if the IEnumerable is null or empty; otherwise, <c>false</c>.
/// </returns>
public static bool IsNullOrEmpty<T>(this ICollection<T> collection)
{
if (collection == null)
{
return true;
}
return collection.Count < 1;
}
}
IEnumerable.Count is O(N), while List.Count is O(1), hence the test for the IList type.