Solution for this annoying error while using a LinqDataSource

Recently, I was making a seemingly harmless LinqDataSource and I came across this error. I was using the simple (I thought):

Where="title.Contains(@title)"

This error kept popping up and confusing me... Contains sure does exist in String, so why the error?

Turns out that it is trying to run Contains on a NULL - and where does that NULL come from? A tricky little property in your ControlParameter that defaults to true, and you have to manually change it to false:

ConvertEmptyStringToNull="false"

And that should cause your Contains to work now, because every string Contains a String.Empty.