Im adding custom validation messages to all my data annotation validation attributes. Simple stuff right. I started off with this.

Then added a customer message.

Then moved that message to a resource file

The problem is the resource file says something like Less than 50. If I change that 50 on the attribute, someone has to remember to go to the resource file and change it there too. Not very DRY.

Luckily the default message formatting will allow us to embed some tokens in the error message.  All we need to do is change our message to Less than {1} and the message is formatted to Less than 50.or whatever the argument value might be.

I haven’t found a good list of the parameters you pass, but {0} is the property name, and then I assume 1, 2, 3, etc are the parameters of the constructor in order.