asp.net mvc - ModelState.IsValid is false when I have a nullable parameter -

i reproduced issue having in brand new mvc web api project.

this default code slight modification.

public string get(int? id, int? = null) {     var isvalid = modelstate.isvalid;     return "value"; } 

if go http://localhost/api/values/5?something=123 works fine, , isvalid true.

if go http://localhost/api/values/5?something= isvalid false.

the issue having if provide null or omitted value item nullable, modelstate.isvalid flags validation error saying "a value required not present in request."

the modelstate dictionary looks this:

with 2 entries something, 1 nullable, not sure if significant or not.

any idea how can fix model valid when nullable parameters omitted or provided null? using model validation within web api , breaks if every method nullable parameter generates model errors.

it appears default binding model doesn't understand nullable types. seen in question, gives 3 parameter errors rather expected two.

you can around custom nullable model binder:

model binder

public class nullableintmodelbinder : imodelbinder {     public bool bindmodel(system.web.http.controllers.httpactioncontext actioncontext, modelbindingcontext bindingcontext)     {         if (bindingcontext.modeltype != typeof(int?))         {             return false;         }          valueproviderresult val = bindingcontext.valueprovider.getvalue(bindingcontext.modelname);         if (val == null)         {             return false;         }          string rawvalue = val.rawvalue string;          // not supplied : /test/5         if (rawvalue == null)         {             bindingcontext.model = null;             return true;         }          // provided no value : /test/5?something=         if (rawvalue == string.empty)         {             bindingcontext.model = null;             return true;         }          // provided value : /test/5?something=1         int result;         if (int.tryparse(rawvalue, out result))         {             bindingcontext.model = result;             return true;         }          bindingcontext.modelstate.addmodelerror(bindingcontext.modelname, "cannot convert value int");         return false;     } } 

usage

public modelstatedictionary get(     int? id,      [modelbinder(typeof(nullableintmodelbinder))]int? = null) {     var isvalid = modelstate.isvalid;      return modelstate; } 

adapted asp.net page: http://www.asp.net/web-api/overview/formats-and-model-binding/parameter-binding-in-aspnet-web-api further reading , alternative method set @ class(controller) level rather per parameter.

this handles 3 valid scenarios:

/test/5 /test/5?something= /test/5?something=2 

this first give "something" null. else (eg ?something=x) gives error.

if change signature to

int? somthing 

(ie remove = null) must explicitly provide parameter, ie /test/5 not valid route unless tweak routes well.