Multiple Get Methods with the Action Method Selector Attribute in .NET Core

Tue, 15 Aug 2017 00:00:00 +0000

Full source code available here.

In .Net Core Web Api it is not possible for the routing mechanism to distinguish between the following action methods.

public string GetSomething(int id, int something)

and

public string GetAnother(int id, int another)

But with the help of an ActionMethodSelectorAttribute we can tell the methods apart.

Step 1

Add a new class called QueryStringConstraint and inherit from ActionMethodSelectorAttribute.

 1public class QueryStringConstraint : ActionMethodSelectorAttribute
 2{
 3 public override bool IsValidForRequest(RouteContext routeContext, ActionDescriptor action)
 4 {
 5 IList<ParameterDescriptor> methodParameters = action.Parameters;
 6
 7 ICollection<string> queryStringKeys = routeContext.HttpContext.Request.Query.Keys.Select(q => q.ToLower()).ToList();
 8 IList<string> methodParamNames = methodParameters.Select(mp => mp.Name.ToLower()).ToList();
 9
10 foreach (var methodParameter in methodParameters)
11 {
12 if (methodParameter.ParameterType.Name.Contains("Nullable"))
13 {
14 //check if the query string has a parameter that is not in the method params
15 foreach(var q in queryStringKeys)
16 {
17 if (methodParamNames.All(mp => mp != q))
18 {
19 return false;
20 }
21 }
22
23 if(queryStringKeys.All(q => q != methodParameter.Name.ToLower()))
24 {
25 continue;
26 }
27 }
28 else if (queryStringKeys.All(q => q != methodParameter.Name.ToLower()))
29 {
30 return false;
31 }
32 }
33 return true;
34 }
35}

Step 2

Add the QueryStringConstraint to the action methods that need to be distinguished by query string parameters.

 1// http://localhost:62922/api/values/?id=1&another=22
 2[QueryStringConstraint]
 3public string GetAnother(int id, int another)
 4{
 5 return $"GetAnother {id} {another}";
 6}
 7
 8// http://localhost:62922/api/values/?id=1&something=22
 9[QueryStringConstraint]
10public string GetSomething(int id, int something)
11{
12 return $"GetSomething {id} {something}";
13}
14
15// http://localhost:62922/api/values/?id=1
16// http://localhost:62922/api/values/?id=1&myNullable=33 
17[QueryStringConstraint]
18public string GetWithNullables(int id, int? myNullable)
19{
20 return $"GetWithNullables {id} {myNullable}";
21}

Full source code available here.

ActionMethodSelectorAttribute | no dogma blog

Multiple Get Methods with the Action Method Selector Attribute in .NET Core

Step 1

Step 2