by J. Ambrose Little
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| Usage The Second Part: Nifty Databinding |
1: <asp:TemplateColumn HeaderText="Favorite Color">
2: <ItemTemplate>
3: <asp:Label runat="server"
Text='<%# ((BizDataBinding.KnightOfRoundTable)
Container.DataItem).Color.Name %>'
ID="Label1">
4: </asp:Label>
5: </ItemTemplate>
6: </asp:TemplateColumn>
7: With this section, I just wanted to demonstrate that you can access the members of each instance in the collection in a very real and binding way by casting Container.DataItem as your object type. As you can see, I've done this to access the Color member of my object in order to display its Name property (ignore the line breaks--they're for printability only). If you just use a BoundColumn or DataBinder.Eval, the ToString() method will be called on the particular member. In the case of Color, this is something like "Color [ColorName]" where ColorName is the actual name of the Color. 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.
To sum up, I have demonstrated how to create a collection of custom objects and bind them to a DataGrid. It's really quite simple once you get down to it--it comes down to just creating a class that implements IEnumerable. Slick, simple, and cool, what more could you ask for from a development framework? |
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User Comments
Title:
help
Name:
Francisco Cruz
Date:
2009-12-17 3:11:43 PM
Comment:
Object Persistance between postbacks
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Title:
Very helpful
Name:
Ben
Date:
2008-09-15 2:22:35 PM
Comment:
just what I needed thanks
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Title:
Mr
Name:
Phillip Knezevich
Date:
2007-02-06 3:45:56 PM
Comment:
It's a geeky example, but I found it useful.
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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.
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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
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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.
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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?
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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.
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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!
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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.
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