Linq Expressions on an Interface

Add to FacebookAdd to DiggAdd to Del.icio.usAdd to StumbleuponAdd to RedditAdd to BlinklistAdd to TwitterAdd to TechnoratiAdd to Yahoo BuzzAdd to Newsvine

One thing I found myself doing quite a bit an often causing logic errors was comparing
dates in Linq queries. For example, if I want to get games that occur between a date range, I might be
doing something like this :

	public static IQueryable<Competition> GetBetweenDates(DateTime startDate, DateTime endDate)
	{
		return (from comp in DataContext.Competitions
				where comp.Date >= startDate && comp.Date <= endDate
				select comp);
	}

I then want to get a list of tournaments that occur between a date range, and I might
essentially rewrite this code using a couple different variables. Rather, I can implement
a common interface on these classes and have an expression applied to all classes that
implement this interface.

	public interface IDate
	{
		DateTime Date { get; set; }
	}
	
	public partial class Competition : DataBase, IDate
	{
		...
	}
	
	public static class Expressions
	{
        public static Expression<Func<T, bool>> GetBetweenDates<T>(DateTime start, DateTime end)
            where T : IDate
        {
            return (t => t.Date >= start && t.Date <= end);
        }	
	}	

Then, rather than rewriting this for each class with a date, I can just apply this expression
to my queries.

	public static IQueryable<Competition> GetBetweenDates(DateTime startDate, DateTime endDate)
	{
		return (from comp in DataContext.Competitions
			select comp).Where(
                             Expressions.GetBetweenDates<Competition>(startDate, endDate));
	}
Advertisements

jQuery Custom Selector for selecting elements by exact text :textEquals

Add to FacebookAdd to DiggAdd to Del.icio.usAdd to StumbleuponAdd to RedditAdd to BlinklistAdd to TwitterAdd to TechnoratiAdd to Yahoo BuzzAdd to Newsvine

I needed a way to find labels based on the text that they contained.  I thought about using :contains() for this, but in this particular case the text items I was searching on were names and I could have similar names that :contains() could incorrectly match on.  For instance, if I was searching for “Banks, Tim” and there was an item with the text “Banks, Timothy” I would get both items returned.  This is not the behavior I was looking for.

I decided to write a little custom selector to match on exact text.  Here is the code for the custom selector:

$.expr[':'].textEquals = function(a, i, m) {
return $(a).text().match("^" + m[3] + "$");
};

What is happening here is I am using a regular expression to test if the start and end of the element’s text matches the string passed in.  Now I could search for the name “Banks, Tim” on a label element like this:

$("label:textEquals('Banks, Tim')");