如何重构这些linq属性?

Question

我有4类属性具有相似的签名，但去不同的linq属性。如何创建委托之类的来清理这个?

例如:

    public IEnumerable<SelectListItem> DistinctUsers
    {
        get
        {
            var list = TraceLogs.OrderBy(x => x.Username).Select(x => x.Username).Distinct();
            return (from s in list select new SelectListItem { Value = s, Text = s }
           );
        }
    }
    public IEnumerable<SelectListItem> DistinctMethods
    {
        get
        {
            var list = TraceLogs.OrderBy(x => x.Method).Select(x => x.Method).Distinct();
            return (from s in list select new SelectListItem { Value = s, Text = s }
           );
        }
    }

Answer 1

听起来你想要这样做:

private IEnumerable<SelectListItem> GetDistinctOrderedLogs<T>
    (Func<TraceLogs, T> extraction)
{
    return TraceLogs.OrderBy(extraction)
                    .Select(extraction)
                    .Distinct()
                    .Select(s => new SelectListItem { Value = s, Text = s });
}

:

public IEnumerable<SelectListItem> DistinctMethods
{
    get { return GetDistinctOrderedLogs(t => t.Method); }
}
public IEnumerable<SelectListItem> DistinctUsers
{
    get { return GetDistinctOrderedLogs(t => t.Users); }
}