I'm on a roll creating extension methods for IDbCommand, so here's another one.

Quite often we see this pattern when reading from a command:

using (var rdr = cmd.ExecuteReader())
{
    while (rdr.Read())
    {
        var thing = new Thing()
        {
            Date = rdr.GetDateTime(0),
            Foo = rdr.GetInt32(1)
        };
        things.Add(thing);
    }
}

It's pretty straight-forward code, but it's code nonetheless. Here's an extension method on IDbCommand that wraps this logic up into one call. It accepts an IList<T> as a parameter, and a function which, given an IDataReader, returns an instance of T:

public static void Fill<T>(this IDbCommand cmd,
    IList<T> list, Func<IDataReader, T> rowConverter)
{
    using (var rdr = cmd.ExecuteReader())
    {
        while (rdr.Read())
        {
            list.Add(rowConverter(rdr));
        }
    }
}

This takes care of wrapping the reader in a "using" statement, so there's one less thing you have to remember to do. If you took the code in the first snippet and wrapped the call to GetDateTime and GetInt32 into its own little extension method on IDataReader called "GetThing", then you'd be able to turn that into this:

cmd.Fill(things, r => r.GetThing());
The less code you have to write, the less the chance you'll introduce bugs, so for me this is a handy method. What do you think? Do you prefer to spell it out, or are extension methods ringing your bell too?