Databinding to Custom Objects: ASP Alliance

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Databinding to Custom Objects

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Published: 09 Oct 2003

Unedited - Community Contributed

Abstract
Easily one of the coolest features of .NET! Learn to create collections for your custom objects that can be bound to a data list.

by J. Ambrose Little
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Article Contents:

"Hey, Old Woman!"

Published: 30 May 2003

(Download C# Source Here)

This has got to be one of the coolest things I've done with ASP.NET in quite some time. I'm binding a collection of my own custom business objects to a DataGrid. No data views, no data readers, only the objects that I made, the way I like them. Even Burger King can't beat this!

What's funny is that it's really quite simple, and had I taken the time to figure it out sooner, I could have been eating Whoppers for a long time now. All you need to do is create a collection class that implements IEnumerable, create a private field as an ArrayList, provide accessors to at least add your custom object to the collection, and of course implement the IEnumerable interface by returning the enumerator from your ArrayList's GetEnumerator method. Then you can use the new collection class as the DataSource for your data list controls.

My Custom Object

1:     /// <summary>

2:     /// Contains information about a knight of the round table.

3:     /// </summary>

4:     public class KnightOfRoundTable

5:     {

6:         private string name = string.Empty;

7:         private System.Drawing.Color color = System.Drawing.Color.Black;

8:         private string quest = string.Empty;

9:     

10:        /// <summary>

11:        /// Knight's Name

12:        /// </summary>

13:        public string Name

14:        {

15:            get

16:            {

17:                return this.name;

18:            }

19:            set

20:            {

21:                this.name = value;

22:            }

23:        }

24:    

25:        /// <summary>

26:        /// Knight's Favorite Color

27:        /// </summary>

28:        public System.Drawing.Color Color

29:        {

30:            get

31:            {

32:                return this.color;

33:            }

34:            set

35:            {

36:                this.color = value;

37:            }

38:        }

39:    

40:        /// <summary>

41:        /// Knight's Quest

42:        /// </summary>

43:        public string Quest

44:        {

45:            get

46:            {

47:                return this.quest;

48:            }

49:            set

50:            {

51:                this.quest = value;

52:            }

53:        }

54:    }

55:

As you can see, it's quite a simple object. Just three members, two string and one Color.

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User Comments

Title: help
Name: Francisco Cruz
Date: 2009-12-17 3:11:43 PM
Comment:
Object Persistance between postbacks

Title: Very helpful
Name: Ben
Date: 2008-09-15 2:22:35 PM
Comment:
just what I needed thanks

Title: Mr
Name: Phillip Knezevich
Date: 2007-02-06 3:45:56 PM
Comment:
It's a geeky example, but I found it useful.

Title: Serialization
Name: Ambrose
Date: 2006-09-21 7:49:08 PM
Comment:
Russ B,

I guess you're trying to use XML serialization like in a Web Service or directly? If so, yeah, it needs an Add method for when it deserializes so that it can add the deserialized instances to the new collection. You just need to implement an Add method, as far as I recall.

Title: Serialization
Name: Russ B
Date: 2006-09-20 4:25:10 PM
Comment:
This is exactly what I've been looking for too.

I tried to serialize your KnightsOfTheRoundTable class and got this error: "System.InvalidOperationException: You must implement the Add(System.Object) method on BizDataBinding.KnightsOfTheRoundTable because it inherits from IEnumerable."

But you did implement Add. Any idea what else needs to be implemented?

...I'm still in 2003

Title: Binding to Complex Properties
Name: J. Ambrose Little
Date: 2005-03-08 9:36:56 AM
Comment:
Hi Mark,

What I was saying is that if you just bind to the Color property, it will print out something like "Color [Black]" instead of the color name, which is really what we're after in this example. So in order to print out the value you want, just access the property of the property that you want to display, e.g., Color.Name. I hope this helps.

Title: Thanks!
Name: Mark Miller
Date: 2005-03-08 12:27:37 AM
Comment:
I was looking around the Internet for an article like this. I'm a bit surprised it was not easier to find.

After finishing my first big web project, I wish I had used a technique like this. Unfortunately too many databinding examples online and in the MSDN docs just show you how to bind to a dataset.

I am a bit confused about the last part, where you say, "So if you do not have control over the ToString method on your class members' types, you may need to use this syntax to specify how you want the bound item to render that member." It seems you're referring to the string "Color [ColorName]", "ColorName" being the name of the color, but I don't know what this syntax would mean in relation to databinding. Aren't you trying to extract the name of the color so that it can display in whatever you are databinding to? What does the "Color [ColorName]" syntax accomplish?

Title: Using CollectionBase
Name: Scott M
Date: 2004-12-12 4:19:12 PM
Comment:
Hey J,

Thanks for the article. I found it really useful. I read (in hardcopy) and article about inheriting from CollectionBase the other day and thought I'd let you know, turns out by your comment that you found it too!

So anyway, cheers and roll on generics,
Scott.

Title: Using CollectionBase
Name: J. Ambrose Little
Date: 2004-08-31 12:53:30 PM
Comment:
Glad the article helped. I've actually found (since this article was published) that inheriting from CollectionBase is even easier than just implementing IEnumerable for my strongly-typed collections. Now I can't hardly wait for 2.0 where we won't even need to bother declaring our own collections and can use the generic ones instead!

Title: Thanks
Name: Scott
Date: 2004-08-31 1:37:07 AM
Comment:
Hey Mr Little, great article. I was a little confused about implementing IEnumerable but once I dissected your example I managed to get my productset (using a dataset stored internally) going to bind it to a asp:repeater... I implemented ienumerator too but your article got me started, so cheers for putting it online.