Optional parameters in ASP.NET Web API
I need to implement the following WebAPI method:
/api/books?author=XXX&title=XXX&isbn=XXX&somethingelse=XXX&date=XXX
All of the parameters can be null, ie the caller can specify from 0 to all the 5 parameters.
In MVC4 beta I used to do the following:
public class BooksController : ApiController
{
// GET /api/books?author=tolk&title=lord&isbn=91&somethingelse=ABC&date=1970-01-01
public string GetFindBooks(string author, string title, string isbn, string somethingelse, DateTime? date)
{
// ...
}
}
MVC4 RC doesn't behave like this anymore. If I specify less than 5 parameters, it replies with a 404 saying
No action was found on the controller 'Books' that matches the request.
What is the correct method signature to make it behave like it used to, without having to specify the optional parameter in the URL routing?
This issue has been fixed in the regular release of MVC4. Now you can do:
public string GetFindBooks(string author="", string title="", string isbn="", string somethingelse="", DateTime? date= null)
{
// ...
}
and everything will work out of the box.
It's possible to pass multiple parameters as a single model as vijay suggested. This works for GET when you use the FromUri parameter attribute. This tells WebAPI to fill the model from the query parameters.
The result is a cleaner controller action with just a single parameter. For more information see: http://www.asp.net/web-api/overview/formats-and-model-binding/parameter-binding-in-aspnet-web-api
public class BooksController : ApiController
{
// GET /api/books?author=tolk&title=lord&isbn=91&somethingelse=ABC&date=1970-01-01
public string GetFindBooks([FromUri]BookQuery query)
{
// ...
}
}
public class BookQuery
{
public string Author { get; set; }
public string Title { get; set; }
public string ISBN { get; set; }
public string SomethingElse { get; set; }
public DateTime? Date { get; set; }
}
It even supports multiple parameters, as long as the properties don't conflict.
// GET /api/books?author=tolk&title=lord&isbn=91&somethingelse=ABC&date=1970-01-01
public string GetFindBooks([FromUri]BookQuery query, [FromUri]Paging paging)
{
// ...
}
public class Paging
{
public string Sort { get; set; }
public int Skip { get; set; }
public int Take { get; set; }
}
Update :
In order to ensure the values are optional make sure to use reference types or nullables (ex. int?) for the models properties.
使用下面所有参数的初始默认值
public string GetFindBooks(string author="", string title="", string isbn="", string somethingelse="", DateTime? date= null)
{
// ...
}
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