CRUD Operations Using Web API 2 And Knockout.js

Introduction

In this article, I will demonstrate how we can perform simple CRUD (Create, Read, Update, Delete) operations using ASP.NET Web API 2 and Knockout.js library. Here, the purpose is to give you an idea of how to use knockout.js with Web API 2. I hope you will like this.

Prerequisites

As I said before, to achieve our requirement, you must have Visual Studio 2015 (.NET Framework 4.5.2) and SQL Server.

In this post, we are going to

• Create MVC application.
• Configuring Entity framework ORM to connect to database.
• Implementing all http Services needed.
• Calling Services using Knockout.js library.

So, let’s understand a bit about knockout.js

What’s Knockout.js?

Knockout is a JavaScript library that helps you to create a rich, responsive display and editor user interfaces with a clean underlying data model. Any time you have sections of UI that update dynamically (e.g., changing depending on the user’s actions or when an external data source changes), KO can help you implement it more simply and maintainably.

Headline features,

• Elegant dependency tracking - automatically updates the right parts of your UI whenever your data model changes.
• Declarative bindings - a simple and obvious way to connect parts of your UI to your data model. You can construct complex dynamic UIs easily using arbitrarily nested binding contexts.
• Trivially extensible - implement custom behaviors as new declarative bindings for easy reuse in just a few lines of code.

SQL Database part

Here, find the script to create database and table.

Create your MVC application

Open Visual Studio and select File >> New Project.

The "New Project" window will pop up. Select ASP.NET Web Application (.NET Framework), name your project, and click OK.

Next, new dialog will pop up for selecting the template. We are going choose Web API template and click Ok button.

After creating our project, we are going to add ADO.NET Entity Data Model.

Adding ADO.NET Entity Data Model

For adding ADO.NET Entity Framework, right click on the project name, click Add > Add New Item. Dialog box will pop up. Inside Visual C#, select Data >> ADO.NET Entity Data Model, and enter a name for your Dbcontext model as CustomerModel.

Next, we need to choose EF Designer from database as model container.

As you can see below, we need to select Server name, then via drop down list, connect to a database panel. You should choose your database name. Finally, click OK.

Now, the dialog Entity Data Model Wizard will pop up for choosing the object which we need to use. In our case, we are going to choose Customers table and click "Finish" button.

Create a Controller

Now, we are going to create a Controller. Right click on the Controllers folder and go to Add > Controller> selecting Web API 2 Controller with actions using Entity Framework > click Add.

In the snapshot given below, we are providing three important parameters

• Model class Customer represents the entity that should be used for CRUD operations.
• Data context class used to establish connection with database.
• Finally, we need to name our Controller (in this case Customers Controller).

As we already know, Web API is a framework that makes it easy to build HTTP services that reach a broad range of clients including browsers and mobile devices.

It has four methods where

• Get is used to select data.
• Post is used to create or insert data.
• Put is used to update data.
• Delete is used to delete data.

CustomersController.cs

Calling Services using Knockout.js library

First of all, we are installing knockout.js library. From solution explorer panel, right click on references > Manage NuGet Packages…

Next, type Knockout.js in search text box, select the first line as below, and click on Install button.

Now, we need to add new js file. Right click on scripts folder > Add > JavaScript File.

App.js

Here, we create our View Model that contains all the business logic, and then, we bind it with ko.applyBindings(new viewModel()) which is enabled to activate knockout for the current HTML document.

As you can see in the below code, ko provides observables to bind to the Model.

• observable() is used to define Model properties which can notify the changes and update the Model automatically.
• observableArray([]) is used to bind list of elements.
  
  1. var ViewModel = function () {
  3. var self = this;
  4. self.CustID = ko.observable();
  5. self.FirstName = ko.observable();
  6. self.LastName = ko.observable();
  7. self.Email = ko.observable();
  8. self.CountryList = ko.observableArray(['Morocco', 'India', 'USA', 'Spain']);
  9. self.Country = ko.observable();
  11. self.customerList = ko.observableArray([]);
  13. var CustomerUri = '/api/Customers/';
  17. function ajaxFunction(uri, method, data) {
  19. //self.errorMessage('');
  21. return $.ajax({
  23. type method,
  24. url uri,
  25. dataType 'json',
  26. contentType 'application/json',
  27. data data ? JSON.stringify(data) null
  29. }).fail(function (jqXHR, textStatus, errorThrown) {
  30. alert('Error ' + errorThrown);
  31. });
  32. }
  35. // Clear Fields
  36. self.clearFields = function clearFields() {
  37. self.FirstName('');
  38. self.LastName('');
  39. self.Email('');
  40. self.Country('');
  41. }
  43. //Add new Customer
  44. self.addNewCustomer = function addNewCustomer(newCustomer) {
  46. var CustObject = {
  47. CustID self.CustID(),
  48. FirstName: self.FirstName(),
  49. LastName self.LastName(),
  50. Email self.Email(),
  51. Country self.Country()
  52. };
  53. ajaxFunction(CustomerUri, 'POST', CustObject).done(function () {
  55. self.clearFields();
  56. alert('Customer Added Successfully !');
  57. getCustomerList()
  58. });
  59. }
  61. //Get Customer List
  62. function getCustomerList() {
  63. $("div.loadingZone").show();
  64. ajaxFunction(CustomerUri, 'GET').done(function (data) {
  65. $("div.loadingZone").hide();
  66. self.customerList(data);
  67. });
  69. }
  71. //Get Detail Customer
  72. self.detailCustomer = function (selectedCustomer) {
  74. self.CustID(selectedCustomer.CustID);
  75. self.FirstName(selectedCustomer.FirstName);
  76. self.LastName(selectedCustomer.LastName);
  77. self.Email(selectedCustomer.Email);
  78. self.Country(selectedCustomer.Country);
  80. $('#Save').hide();
  81. $('#Clear').hide();
  83. $('#Update').show();
  84. $('#Cancel').show();
  86. };
  88. self.cancel = function () {
  90. self.clearFields();
  92. $('#Save').show();
  93. $('#Clear').show();
  95. $('#Update').hide();
  96. $('#Cancel').hide();
  97. }
  99. //Update Customer
  100. self.updateCustomer = function () {
  102. var CustObject = {
  103. CustID self.CustID(),
  104. FirstName self.FirstName(),
  105. LastName self.LastName(),
  106. Email self.Email(),
  107. Country self.Country()
  108. };
  110. ajaxFunction(CustomerUri + self.CustID(), 'PUT', CustObject).done(function () {
  111. alert('Customer Updated Successfully !');
  112. getCustomerList();
  113. self.cancel();
  114. });
  115. }
  117. //Delete Customer
  118. self.deleteCustomer = function (customer) {
  120. ajaxFunction(CustomerUri + customer.CustID, 'DELETE').done(function () {
  122. alert('Customer Deleted Successfully');
  123. getCustomerList();
  124. })
  126. }
  128. //Chart Line function used to display a chart which represents nb of customers by country
  129. function chartLine() {
  131. ajaxFunction('http//localhost50706/Customers/GetCustomerByCountry', 'GET').done(function (result) {
  132. console.log(result);
  133. Morris.Line({
  134. element 'line-chart',
  135. data result,
  136. xkey 'CountryName',
  137. // A list of names of data record attributes that contain y-values.
  138. ykeys ['value'],
  139. // Labels for the ykeys -- will be displayed when you hover over the
  140. // chart.
  141. labels ['Value'],
  143. parseTime false
  144. });
  147. });
  149. };
  151. chartLine();
  152. getCustomerList();
  154. };
  156. ko.applyBindings(new ViewModel());

Now, from Solution Explorer panel, we are going to add index.html file as shown below.

Index.html

In order to exchange the data between HTML page and JavaScript file, knockout.js offers various types of bindings that should be used within data-bind attribute.

• Click represents a click event handler to call JavaScript function.
• Value represents the value binding with UI element’s to the property defined into view Model.
• Text represents the text value to the UI element.
• Foreach used to fetch an array.

Now, you can run your application. Don’t forget to change the URL address as below.

http//localhost55192/index.html

Let’s see the output.

That’s all, Please send your feedback and queries in comments box.