ASP.Net: Is it possible to skip databinding of an element if an error occurs?

Question

Hey everyone,

I use a lot of repeaters for different elements of our sites, and I've always wondered if there was a way to have the repeater skip an element if an exception occurs instead of having the whole page crash?

In particular, I've inherited a system from another developer that using a similar design, however he didn't include any kind of validation for his business objects, and it a single property is missing, the whole thing goes up in smoke.

Any suggestions?

Thanks in advance!

Answer 1

The simplest suggestion I can offer is the check the validity of the data before it's passed to the repeater. I don't believe there's any way to get the stock repeater to skip a data element on error.

The other approach is to build your own repeater, inheriting from the base Repeater, to add that functionality but I've no sample code to offer. Perhaps someone else may be able to help there.

Answer 2

The way I see it, you have at least three options.

1. You could create a custom repeater control that inherits System.Web.UI.WebControls.Repeater and override the databinding behaviour to be more try-catchy (probably fail silently on databinding errors). You couldd then easily replace all instances of the standard Repeater with this new one.
2. You could filter your datasources before databinding to remove items you know are going to cause problems beforehand. This option may be quite laborious and something of an iterative process.
3. You could try adding default values to the business objects, so that the properties you're binding to return a default instance rather than null (not nice either).

That's my thoughts anyway.

One question - you say "when a property is missing". Do you mean he's using a style of databinding syntax that offers no compile-time checking and is referencing properties that don't exist, or is referecing properties that are null?

Edit

OK, so you're referencing properties that are null. If you have access to the code for the business objects you could modify them so they return a new, non-null instance (this is the third option I gave).

You don't say if you're using .net 3.5, but I'll assume you are. You could add a new property "IsValidForDataBinding" on to each of your business objects. In the getter logic you could check each of the necessary properties and sub-objects to check for validity, non-nullness etc and return a bool. When you come to bind your repeater, write a simple linq statement that filters-out the invalid items (i.e. where IsValidForDataBinding = false). Having said that, I still think that writing a derived repeater control could be your easiest option.

Answer 3

Have you tried using string.isnullorempty("the string") to check for a value before referencing the property?

Here's a reference: MSDN