I prefer to use the abstract IList interface in my public APIs, rather than passing around concrete List implementations. However, the one thing I’ve always missed was the awesome .ForEach syntax which was available on the List implementation.

Today, I realized that I can use extension methods to add methods to interfaces.

public static class ListExtensions
{
    public static void ForEach<T>(this IList<T> source, Action<T> action)
    {
        foreach (T item in source)
            action(item);
    }
}

This now allows me to do things like:

public static void Main(string[] args)
{
    IList<string> items = GetItems();
    items.ForEach(Console.WriteLine);
}
 
private static IList<string> GetItems()
{
    return new List<string> { "abc", "123" };
}

I much prefer this syntax to the foreach construct.

I was doing some testing on a javascript abstraction that we created earlier. In order to test that the validation was being properly called, I wanted to drop in a new target javascript and then use WatiN to execute and validate the various calls to that javascript.

I came up with (what I think is) a neat semantic for doing this. The SwappedFile implements the IDisposable interface, so you can wrap it up nicely in a using statement and make sure that the original file is reverted when completed.

class SwappedFile : IDisposable
{
    private readonly string originalFile;
 
    public SwappedFile(string originalFile, string newFile)
    {
        if (String.IsNullOrEmpty(originalFile)) throw new ArgumentNullException("originalFile");
        if (String.IsNullOrEmpty(newFile)) throw new ArgumentNullException("newFile");
 
        this.originalFile = originalFile;
 
        if (!File.Exists(String.Format("{0}-original", originalFile)))
        {
            File.Move(originalFile, String.Format("{0}-original", originalFile));
        }
 
        File.Copy(newFile, originalFile, true);
    }
 
    public void Dispose()
    {
        File.Delete(originalFile);
        File.Move(String.Format("{0}-original", originalFile), originalFile);
    }
}

Usage is simple:

using (new SwappedFile("original-file.txt", "new-file.txt"))
{
    // some operations using the new file
}

I kinda like this, plus it beats having all of my code cluttered up with file manipulation statements.