Working example of AngularJS $resource searching items in Web Api

Question

I'm learning how to use AngularJS's $resource to call a Web Api backend. I want to pass an object hierarchy in as criteria and get back an IEnumerable<Program>. Here's an example of the criteria:

$scope.criteria = {
    Categories:[
        {
            Name: "Cat1",
            Options: [
                {Text: "Opt1", Value: true},
                {Text: "Opt2", Value: false}
            ]
        },
        {
            Name: "Cat2",
            Options: [
                {Text: "Opt3", Value: true},
                {Text: "Opt4", Value: false}
            ]
        }
    ]
}

I have the same objects defined on the server in C#.

public class CriteriaModel
{
   public IEnumerable<CriteriaCategory> Categories { get; set; }
}

public class CriteriaCategory
{
    public string Name { get; set; }
    public IEnumerable<CriteriaOption> Options { get; set; }
}

public class CriteriaOption
{
    public string Text { get; set; }
    public bool Value { get; set; }
}

Here's how I am configuring $resource:

angular.module('my.services')
    .factory('api', [
        '$resource',
        function ($resource) {
            return {
                Profile: $resource('/api/profile/:id', { id: '@id' }),
                Settings: $resource('/api/settings/:id', { id: '@id' }),
                Program: $resource('/api/program/:id', { id: '@id' })
            };
        }
    ]);

And I call it like this:

api.Program.query({ criteria: $scope.criteria }, function (response) {
    $scope.programs = response;
});

No matter what I try I either get null as the criteria parameter or the action doesn't execute at all. I don't know if the problem is in angular, web api, or both. Here is the action:

public class ProgramController : ApiController
{
    public IEnumerable<Program> GetByCriteria([FromUri]CriteriaModel criteria)
    {
        // Either criteria is null or this action doesn't even get
        // executed depending on what I try.
    }
}

Can someone help me get a working example going for searching and returning items using AngularJS $resource and Web Api?

Organ

Answer 1

You're going to need a custom model binder. From what I understand FromUri will not handle complex nested types or json which $resource will put in the query string.

Model binder:

public class CriteriaModelBinder : IModelBinder
{
    public bool BindModel(
        HttpActionContext actionContext,
        ModelBindingContext bindingContext
    )
    {
        if (bindingContext.ModelType != typeof (CriteriaModel))
        {
            return false;
        }

        var value = bindingContext.ValueProvider.GetValue("Categories");

        if (value == null)
        {
            return false;
        }

        var categoryJson = value.RawValue as IEnumerable<string>;

        if (categoryJson == null)
        {
            bindingContext.ModelState.AddModelError(
                bindingContext.ModelName, "Categories cannot be null.");
            return false;
        }
        
        var categories = categoryJson
            .Select(JsonConvert.DeserializeObject<CriteriaCategory>)
            .ToList();

        bindingContext.Model = new CriteriaModel {Categories = categories};
        return true;
    }
}

Controller:

[RoutePrefix("api/program")]
public class ProgramController : ApiController
{
    [Route("getbycriteria")]
    [HttpGet]
    public HttpResponseMessage GetByCriteria(
        [ModelBinder(typeof(CriteriaModelBinder))]CriteriaModel criteria
    )
    {
        return new HttpResponseMessage(HttpStatusCode.OK);
    }
}

Angular Controller:

angular.module('myApp').
    controller('HomeController', function($scope, $resource) {
        var Program = $resource('/api/program/:id', {}, {
            getByCriteria: {
                url: '/api/program/getbycriteria',
                method: 'GET',
                isArray: true
            }
        });

        var program = new Program();
        var criteria = {
            Categories: [
                {
                    Name: "Cat1",
                    Options: [
                        { Text: "Opt1", Value: true },
                        { Text: "Opt2", Value: false }
                    ]
                },
                {
                    Name: "Cat2",
                    Options: [
                        { Text: "Opt3", Value: true },
                        { Text: "Opt4", Value: false }
                    ]
                }
            ]
        };

        $scope.submit = function () {
            console.log(program);
            program.$getByCriteria(criteria);
        };
    });

Edit:

Here is for POST:

Controller:

[RoutePrefix("api/program")]
public class ProgramController : ApiController
{
    [Route("getbycriteria")]
    [HttpPost]
    public HttpResponseMessage GetByCriteria(CriteriaModel criteria)
    {
        return new HttpResponseMessage(HttpStatusCode.OK);
    }
}

Angular:

angular.module('myApp').
    controller('HomeController', function($scope, $resource) {
        var Program = $resource('/api/program/:id', {}, {
            getByCriteria: {
                url: '/api/program/getbycriteria',
                method: 'POST',
                isArray: true
            }
        });

        var program = new Program();
        program.Categories = [
                {
                    Name: "Cat1",
                    Options: [
                        { Text: "Opt1", Value: true },
                        { Text: "Opt2", Value: false }
                    ]
                },
                {
                    Name: "Cat2",
                    Options: [
                        { Text: "Opt3", Value: true },
                        { Text: "Opt4", Value: false }
                    ]
                }
            ];

        $scope.submit = function () {
            console.log(program);
            program.$getByCriteria();
        };
    });

Ramah

So if I created a new action in $resource which does a POST and took [FromUri] off the parameter, would that take care of it without me having to create a custom model binder? – Organ

The default model binder looks for JSON in the body of the request. $resource is RESTful and sends JSON in the query string. The mismatch is why you need to either use a model binder or use $http. – Ramah

Wait, I'm confused. You can specify a new action on $resource with a method of 'POST' according to the documentation. Are you saying it ignores that and puts it in the querystring anyway? – Organ

Yes you can change the action to POST except you will need to attach the Categories directly to the program object. – Ramah

I would recommend against using POST unless you are intending to do an operation with side effects. – Ramah

That makes a lot of sense now. I have a large number of criteria so I may not have a choice of whether I can use GET vs POST. Thanks for your help. – Organ