ASP.NET Web Form Model Binding + Web API

Nowadays, many people are talking about Web API and some developers came to me and ask for sample code about how to call an ASP.NET Web API by using the HttpClient class library. Today, I want to share how to send HTTP GET, POST, PUT and DELETE to the ASP.NET Web API from a web page that perform simple CRUD operation.

I have created a very simple address book web application that can display and manipulate the data from the Web API. To begin with the ASP.NET Web API development, create a new empty web project from Visual Studio.

Select the Empty template, as I want to create the latest Web API (version 2.2) by getting the latest assembly from NuGet later.

From the newly created project, open NuGet Package Manager, then search for Microsoft ASP.NET Web API 2.2, then install it.

As I am using the Map HTTP Attribute Routes method to define my routes, therefore, create the class WebApiConfig as follow:

public class WebApiConfig

{

    public static void Register(HttpConfiguration config)

    {

        // Web API routes

        config.MapHttpAttributeRoutes();

    }

}

In the same project, add new Global.asax file if not exist. Then, at the Application_Start event, add this line of code:

GlobalConfiguration.Configure(WebApiConfig.Register);

Service

Now, proceed to create a new controller that support Get, List, Create, Update and Delete function by using HttpGet, HttpPost, HttpPut and HttpDelete attributes like following code:

[RoutePrefix("api/AddressBook")]

public class AddressBookController : ApiController

{

    // GET api/<controller>

    [Route]

    [HttpGet]

    public List<AddressBook> Get()

    {

        AddressBookComponent bc = new AddressBookComponent();

        return bc.List();

    }

    // GET api/<controller>/5

    [Route("{id:int}")]

    [HttpGet]

    public AddressBook Get(int id)

    {

        AddressBookComponent bc = new AddressBookComponent();

        return bc.Get(id);

    }

    // POST api/<controller>

    [Route]

    [HttpPost]

    public void Create(AddressBook addressBook)

    {

        AddressBookComponent bc = new AddressBookComponent();

        bc.Create(addressBook);

    }

    // PUT api/<controller>/5

    [Route("{id:int}")]

    [HttpPut]

    public void Put(int id, AddressBook addressBook)

    {

        AddressBookComponent bc = new AddressBookComponent();

        bc.Update(addressBook);

    }

    // DELETE api/<controller>/5

    [Route("{id:int}")]

    [HttpDelete]

    public void Delete(int id)

    {

        AddressBookComponent bc = new AddressBookComponent();

        bc.Delete(id);

    }

}

[RoutePrefix("api/AddressBook")] attribute is used to create a template URL for your API. As the example above, the Web API URL is base at http://localhost:<port>/api/AddressBook

[Route] attribute is used to make an URL that base on the URL defined in RoutePrefix attribute which link to the particular method directly. For this case, I never specify any named parameter to the Route attribute, hence the URL to call this web function is the same, which is http://localhost:<port>/api/AddressBook. The incoming request will route to the correct function base on the supplied HTTP Verb.

[Route("{id:int}")] has specified named parameter. This attribute will route the request URL that contain parameter with integer type to that particular function. In this case, the URL that will hit that function is http://localhost:<port>/api/AddressBook/5

[Route("{id:int}")]

[HttpPut]

public void Put(int id, AddressBook addressBook)

Note that the above HTTP PUT method contain 2 parameters, one is the ID and another is the object. This is the standard PUT method declaration. If you have the method without the ID parameter, you will get HTTP 405 Method Not Allowed error because it will treat it as POST even you had specified HttpPut attribute.

Client

Now, start to create the client that will consume the above Web API. The Web API can only support JSON and XML HTTP content type, and I pick JSON for light weight payload and it is the commonly used format nowadays. We just need to make sure the HTTP request that sent to the Web API contain the content-type : application/json in the HTTP header. And to do that, I use HttpClient class which comes from the Microsoft ASP.NET Web API 2.2 Client Libraries. You can obtain it from NuGet:

In today's topic, I will also cover about how to use model binding in grid view (ASP.NET Web Form not MVC).

NOTE: Before you begin, I expect that you already had an entity or object which defined as a model.

Create a new ASP.NET web form project, then create a new page. Put a grid view in the page, then define the grid view like this:

<asp:GridView ID="addressBookGrid" runat="server"

    ItemType="AddressBookSample.Entities.AddressBook"

    SelectMethod="addressBookGrid_GetData"

    UpdateMethod="addressBookGrid_UpdateItem"

    DeleteMethod="addressBookGrid_DeleteItem"

    DataKeyNames="ID">

    <Columns>

        <asp:CommandField ShowDeleteButton="True" ShowEditButton="True" />

    </Columns>

</asp:GridView>

First, put the model as the ItemType. Then, define the SelectMethod, UpdateMethod and DeleteMethod, when you do it, Visual Studio will automatically suggest, create and map the events for you. Put the model property name in the DataKeyNames which you think it is unique and can be an identifier for your object.

HTTP GET

The following is the implementation for the SelectMethod. It will send HTTP GET request to the Web API, then bind the responded data into the grid view automatically.

public IQueryable<AddressBook> addressBookGrid_GetData()

{

    HttpClient client = new HttpClient();

    client.BaseAddress = new Uri("http://localhost:5593");

    client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));

    HttpResponseMessage response = client.GetAsync("api/AddressBook").Result;

    response.EnsureSuccessStatusCode();

    List<AddressBook> addressBooks = response.Content.ReadAsAsync<List<AddressBook>>().Result;

    return addressBooks.AsQueryable();

}

HTTP POST

The following is the implementation for a Create button. I have a form with text boxes and the Create button to let user enter the information that will be sent to the Web API.

protected void btnCreate_Click(object sender, EventArgs e)

{

    AddressBook addressBook = new AddressBook()

    {

        ID = Convert.ToInt32(createID.Text),

        FirstName = createFirstName.Text,

        LastName = createLastName.Text,

        Contact = createContact.Text

    };

    HttpClient client = new HttpClient();

    client.BaseAddress = new Uri("http://localhost:5593");

    client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));

    HttpResponseMessage response = client.PostAsync<AddressBook>("api/AddressBook", addressBook, new JsonMediaTypeFormatter()).Result;

    response.EnsureSuccessStatusCode();

}

HTTP PUT

The following is the implementation for the UpdateMethod. The method will automatically have the id parameter value which you had selected from the grid view, the code will send HTTP GET request to the Web API to retrieve the specific object first, then update the object, finally send the object with HTTP PUT request to the Web API.

public void addressBookGrid_UpdateItem(int id)

{

    HttpClient client = new HttpClient();

    client.BaseAddress = new Uri("http://localhost:5593");

    client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));

    HttpResponseMessage response = client.GetAsync("api/AddressBook/" + id).Result;

    response.EnsureSuccessStatusCode();

    AddressBook item = response.Content.ReadAsAsync<AddressBook>().Result;

    // Load the item here, e.g. item = MyDataLayer.Find(id);

    if (item == null)

    {

        // The item wasn't found

        ModelState.AddModelError("", String.Format("Item with id {0} was not found", id));

        return;

    }

    TryUpdateModel(item);

    if (ModelState.IsValid)

    {

        // Save changes here, e.g. MyDataLayer.SaveChanges();

        HttpResponseMessage updateResponse = client.PutAsync<AddressBook>("api/AddressBook/" + id, item, new JsonMediaTypeFormatter()).Result;

        response.EnsureSuccessStatusCode();

    }

}

HTTP DELETE

The following is the DeleteMethod implementation. The method will also automatically have the ID parameter value which you had selected from the grid view, just simply send the ID with HTTP DELETE request to the Web API as follow:

public void addressBookGrid_DeleteItem(int id)

{

    HttpClient client = new HttpClient();

    client.BaseAddress = new Uri("http://localhost:5593");

    client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));

    HttpResponseMessage response = client.DeleteAsync("api/AddressBook/" + id).Result;

    response.EnsureSuccessStatusCode();

}

That's it for a simple CRUD web application that deal with Web API. If you are interested with my source code, feel free to download it from HERE.