ASP.NET Autocomplete Textbox Using jQuery, JSON and AJAX

Step 8: Add an ASP.NET Web service file named "CountriesService.asmx" and replaced it with the following code.




Press Ctrl + F5 to check that our service is working as expected or not. You will see the following screen.



Click the link GetCountriesDetails which is the name of the method that we created in Service code. You will see the following.



When you enter some characters and press invoke, it will fetch the data from the database using the Stored procedure that we created in SQL.



Understanding the code of Web service.

• We will use the auto implemented properties defined in Countries.cs class file.
  
  
• In the web service we are using the simple ADO.NET connectivity to fetch data using Stored procedure.
  
  
• The data that we get from database is stored in List object of Countries class. So, a list of countries is maintained in it.
  
  
• At the end of code, we are using JavascriptSerializer Class's object which will serialize all the list data into JSON format that we will use in our jQuery code to show suggestions in textbox.

Step 9: Add a new Webform named "Demo.aspx" and add the reference of the following jQuery files to its head section.



Step 10: Add the following code to HTML Source of Demo.aspx page.

Step 11: Verify that our Solution Explorer should look like the following image. I mean that all the below mentioned files/folder should be available.



Step 12: Now press Ctrl + F5 and you will see that our objective is completed.





Understanding the HTML and jQuery Code

• We have taken a textbox in the body of HTML page.
  
  
• In Jquery code, we have used some properties of AJAX and Autocomplete Widget, to understand their purposes, you can refer to their definitions from jqueryui.com and jquery.com.

Code Explanation:

• At the very first, in ready function of jQuery, we are finding the textbox using its ID and to that we applied autocomplete function of jQuery.


• minLength tells that the minimum character to be entered by the user should be one.
  
  
• Source tells what will be the source for autocomplete feature to work, so we created a function that sends the user entered value to our web service which expects a parameter called "term". All this will occur at the request end. When the service completes its work, we specify the method as 'post' which will only work when we get the response from the web service. That's why the function here has two parameters i.e. request and response.
  
  
• As our web service is returning that data in JSON format, so we specify datatype as JSON.
  
  
• The data is term that we send to the service.
  
  
• If the data is success, then we return back data in the function and send it to response parameter of source function.
  
  
• If the error occurs, it will show a JavaScript alert.
  
  
• Focus and select will keep the focus on textbox. This is implemented to show the data in textbox even if we hover mouse cursor over. For this we created a separate function which shows the hovered/selected list item of autocomplete in the textbox.
  
  
• Again we call autocomplete function, to that we call _renderItem method which creates a list of returned data in <li> tag format.
  
  
• RenderItem expects two parameters, ul and item. So, we returned a <li> tag using jQuery and to that we append image tag which shows the image.
  
  
• To the above, we again append the name of country.
  
  
• And we added all this appended data to <ul> and returned the item.
  
  
• We also added some style to set the width and height of the image because image can be of different sizes.

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