Web API single string parameter validation using validation attributes
asp.net, asp.net-web-api, c#
Solution
If you're using Attribute Routing to manage your paths coming into your controllers, you can always do something like this:
[Route("{Id:regex([0-9]{0,10})}")]
public async Task<HttpResponseMessage> Get(string id)
{
}
There are various route contraints, as documented on the Attribute Routing overview documentation.
It does raise the question as to why you're accepting a numeric string of length 10 as your id. you'll have to be careful when parsing it into an int that it doesn't exceed `2,147,483,647`, as that's the maximum size for a default integer.
Problem
I know that you can use Validation attributes on a model to validate it like so: ``` public class CommunicationQuery { [RegularExpression("[0-9]{0,10}", ErrorMessage = "Please enter a valid policy number")] public string PolicyId { get; set; } [RegularExpression("[0-9]{0,10}", ErrorMessage = "Please enter a valid member number")] public string MemberId { get; set; } } public IEnumerable<Communication> Get([FromUri]CommunicationQuery documentQuery) { } ``` But is it possible to validate a single string using validation attributes such as this? ``` public async Task<HttpResponseMessage> Get([RegularExpression("[0-9]{0,10}")]string id) { } ``` This didn't seem to work. The only ways I've been able to do this was to either create a wrapper object and use `[FromUri]`, use a custom `ActionFilterAttribute` on the action itself or to manually validate the parameter in the controller action using a regular expression.