Geeks With Blogs


Google My Blog

Catch me at: The List!

My InstallScript Utility Belt My Amazon Wishlist
My Standard Disclaimer

Chris G. Williams Beware: I mix tech and personal interests here.

Wanna see something neat?  Create an ASPX page in Visual Studio and add a GridView Control. Leave the name as GridView1.

(You can do this any number of ways, but I happened to do it in an aspx page.)

In your codebehind page, add the following to the form.Load event:

Protected Sub form1_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles form1.Load
    Dim filter As String = "System"
    Dim query = From a In AppDomain.CurrentDomain.GetAssemblies() _
                Where a.GetName().Name.Contains(filter) _
                Select a.GetName.Name

    'filter = "Xml"

    GridView1.DataSource = query
End Sub


Now run the page. You should see something that looks like this:


You should be looking at a list of Namespaces that begin with "System."  Once you're done ooh'ing and ahh'ing over it, go back to your codebehind page and uncomment the 'filter = "Xml" line.

Now you're probably thinking, so what Chris, it's not going to do anything because it's AFTER the query...  But that is where you'd be wrong. See there's this thing called Deferred Execution, and it's part of LINQ. It gives us a lot of flexibility. Trust me on this.

So, if you uncomment that line, and run the code again, this time you should see something like this:


I know, crazy huh?

What happens is this... when you create your query, it's not actually executing until you need it. In this case, it's the databind. In other cases, it might be when you call the .ToArray method of your resultset, or when you add the contents to a custom object.



Posted on Thursday, March 20, 2008 6:04 PM | Back to top

Comments on this post: Deferred Execution in LINQ

# re: Deferred Execution in LINQ
Requesting Gravatar...
great article, very usefull for us...thank you
Stop Dreaming Start Action

Left by Rusli Zainal Sang Visioner on Aug 12, 2009 10:42 PM

Your comment:
 (will show your gravatar)

Copyright © Chris G. Williams | Powered by: