Contents tagged with DataControls
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Invalid postback or callback argument
I'm sure many of you have seen this error message when developing your web application:
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A new way to DataBind()
The Problem
I've been thinking alot recently about the problems with data binding (and they're alot). There are some patterns that play well with ASP.NET (and are repeated everywhere) and some that don't quite fit the model. One of those patterns that don't mesh well is, setting the DataSource property of any of the DataControls. Before ASP.NET 2.0 and DataSource controls we'd have to set the DataSource property and manually call DataBind. -
AutoFieldGenerators
In 3.5 SP1 we added new properties to GridView and DetailsView which allows the page developer to change the way AutoGenerateColumns creates its columns. This feature is well know in Dynamic Data, but it is not tied to this technology. Dynamic Data takes advantage of this by looking at the meta data that users set on properties to generate columns.
You too can roll your own IAutoFieldGenerator. Lets look at the interface: -
How <%# Bind %> Works
In my last post I spoke about 2-way databinding and how it can be used to extract values from control properties. How does this all work? Lets take a look at a page with 2-way databinding:
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Getting your data out of the data controls
After you've created a layout with a data control of your choice and eventually bound them to some datasource, you almost always want to get that data back out of them(and why wouldn't you, its your data). One thing you'll learn about developing asp.net webpages is that its like petting a porcupine (yikes). If you go with the flow, you probably won't get stuck, but the moment you try to go against the grain you end up with a hand full of thorns.
Most of the data controls have events ending in ing and ed e.g. RowUpdating, RowUpdated etc. In most of the event handlers of the ing events it is easy to get the values from the event args.