Month: May 2010

I never got used to the .NET Uri type. It seems like I only had to use it occasionally and even then where I really only wanted to type a string url.

public static Uri AsUri(this string uri) { return new Uri(uri); }

This way I can just add a AsUri() when I forgot that I was supposed to pass a Uri instead of a string.

webclient.DownloadFileAsync( “http://blah.com”, filename );

doesn’t compile and so I can scratch my head once again and replace it.

webclient.DownloadFileAsync( “http://blah.com”.AsUri(), filename );

I like trivial things 🙂

I don’t think I like the name, but I couldn’t come up with something better.

public static bool IsWithin(this DateTime datetime, TimeSpan distance) {
  var now = DateTime.Now;
  return (now – datetime).Duration() < distance;
}
public static bool IsWithin(this DateTime datetime, TimeSpan distance, DateTime now) {
  return (now – datetime).Duration() < distance;
}

Coupled with extension methods from yesterday you can write code like this:

if ( postDate.IsWithin(24.Hours()) ) { … }

nice and readable.

Ok, the ruby lovers will laugh, the ruby haters will, well, hate.

public static TimeSpan Minutes (this int minutes) {
  return new TimeSpan(0, minutes, 0);
}
public static TimeSpan Hours (this int hours) {
  return new TimeSpan(hours, 0, 0);
}
public static TimeSpan Seconds (this int seconds) {
  return new TimeSpan(0,0, seconds);
}

So that now I can write readable code like this:

var fiver = 5.Seconds();
var fivertoo = 5.Hours();
Assert.That( fiver.IsLessThan(fivertoo) );

Alright, I’ll admit it, this one is rather obscure and only useful if you are doing strange things with a Windows Forms DataGridView.

I like this method because I think its a good use of Fold… err.. I mean Aggregate. I’m convinced Aggregate is an underutilized method so far by .NET developers.

In this case I like it because I can state what I want to do in a single statement rather than multiple statements.

public static IDictionary<int, string> GetDisplayIndexToPropertyNameMap(this DataGridView datagridview)
{
  var boundColumns = 
          datagridview.Columns.Cast<DataGridViewColumn>().Where(c => null != c.DataPropertyName);
  return boundColumns.Aggregate(
                new Dictionary<int, string>(),
                (a, b) => a.Insert(b.DisplayIndex, b.DataPropertyName));
   }

Notice the use of yesterday’s Dictionary.Insert so that we return the Dictionary at every iteration of the Aggregate*.

I find this MUCH more readable than if the Aggregate statement had been

return boundColumns.Aggregate(new Dictionary<int,string>(),
   (a,b) => { a.Add(b.DisplayIndex, b.DataPropertyName); return a; } );

The curly braces for the block lambda syntax and the return statement inside them really take away from the readability IMO.

* Note that this is why I put Insert explicitly on Dictionary instead of IDictionary. C# 3’s type inference is not good enough to figure out that we would want the signature of Aggregate to be IDictionary<int,string> instead of Dictionary<int,string> if Insert returned an IDictionary

Yes, this is a horrible name. If you have a better suggestion, I’m very welcome to it.

Here is the point: I want a method on Dictionary that does what Add does, but returns the dictionary instead of void. That way I can do this.

var d = (new Dictionary<string,string>()).Insert(“hi”,”mom”).Insert(“hello”,”dad”).Insert(“peace”,”sista”).Insert(“word”,”brotha”)

And yes, I know that C# 3’s initializer syntax lets me do this instead:

new Dictionary { { “hi”,”mom” }, {“hello”,”dad”}, {“peace”,”sista”}…}

BUT… that only works with a constructor. Tomorrow’s edition will show why I want a method instead of an initializer.

* I didn’t know that initializer is not a dictionary word. I love when fields (programming) extend their own words.