Return an error when invalid parameters are specified in ASP Web API

Question

I\'m creating an API using C# and ASP.NET Web API and I want it to return an error when a parameter is used that isn\'t recognised.

For example:

/api/Eve         


        

Answer 1

You could create an ActionFilter to automate this:

public class InvalidQueryStringRejectorAttribute : ActionFilterAttribute
{
    public override void OnActionExecuting(HttpActionContext actionContext)
    {
        var arguments = actionContext.ActionArguments.Keys;

        var queryString = actionContext.Request.GetQueryNameValuePairs()
            .Select(q => q.Key);

        var invalidParams = queryString.Where(k => !arguments.Contains(k));

        if (invalidParams.Any())
        {
            actionContext.Response = actionContext.Request.CreateResponse(HttpStatusCode.BadRequest, new
            {
                message = "Invalid query string parameters",
                parameters = invalidParams
            });
        }
    }
}

That filter will reject any request with query string parameters that do not match the method signature.

You may use it like this:

[InvalidQueryStringRejector]
public IHttpActionResult Get(string value)
{
    return Ok(value);
}

Or apply to any action by registering it inside your HttpConfiguration object:

config.Filters.Add(new InvalidQueryStringRejectorAttribute());