The code for the done function is as follows:. When using ajax , the data transfer is drastically reduced. The two images below show the amount of data transferred when initially loading the user table and when clicking a row in that table to load user details. The image above on the left shows that clicking the Load Users button results in a data transfer of bytes, as shown below. The image above on the right shows that clicking a row in the Users GridView control results in a transfer of bytes, as shown below.
So, by using ajax the size of the data transferred each time a row in the Users GridView is clicked is reduced from 5. That's a significant decrease in data which should result in a similar improvement in performance.
You might find, while you're refactoring your code, that it makes sense to replace some of the ASP. That example page defines the table structure for the Users table, but leaves the table body empty so it can be filled when the data arrives:.
The done function that is called when the GetUsers WebMethod returns uses the jQuery templating plugin see references at the end of this article. In the JQueryAjax. The template used in that done function is defined in the JQueryAjax. The data passed to the template function contains the basic information for the user, along with an ID that is used to look up user details when a row is clicked.
The template is shown below:. In other cases it might be better to retain the ASP. NET controls, especially in the case of the more complex ones, such as the Login or AdRotator controls. You might also have custom controls that you don't want to replace. It only makes sense to replace ASP. NET controls if doing so provides some performance benefit or simplifies your code.
The focus should be on reducing postback-related data transfers, and jQuery. Another option is to define just the bare minimum of HTML controls on the page and retrieve the remaining controls with ajax calls. The AjaxGetHtml page of the example application demonstrates this. The page the user initially loads has just a button and two div tags, one for the users table and one for user details. The WebMethods that are called by ajax prepare the HTML that go into those div tags, and the jQuery done methods that handle the returning data just plug it into the page.
In a real-world application we probably wouldn't send the html on every click, since sending just the data as a JSON string is more efficient. There might be cases, however, where that would make sense. For instance, suppose we had a page that presented several different complex views, but we knew that a user generally opened just one of them.
In that case we might provide an empty div for each of those views and fill out the ones the user chooses to visit. Instead of sending the html for an entire div each time one of them needs to be updated, however, we might check if the div is empty and only send the html the first time. In the below example, we send list of employees to create in database and get all employees. The method needs to be public, static, and add an attribute as WebMethod on top of it.
The length of the string exceeds the value set on the maxJsonLength property. To solve the above problem, we need to increase the default value of MaxJsonLength.
F or that, set the MaxJsonLength property value in web. Also, we saw how it can be implemented in ASP. Hope this helps. View All.
Manas Mohapatra Updated date Nov 15, Reduces the traffic travels between the client and the server. Add following code in Controller action. There are two types of the BeginForm extension methods: Html. AllowCache It is the boolean property which indicates whether to allow cache or not.
Step 1 Add the following User Model in Models folder. Step 2 Add the code for action AddUser to Controller. Step 3 Add the following code to define Aax. Step 1 Add the following action in Controller which gets the list of users from datasource and returns as JSON format. Next Recommended Reading. Windows 10 Vs Windows Notice, just as in the standard. The next set of functions you will add perform the work of finding the tasks and either updating or deleting the objects from the collection.
These functions are responsible for using the functions I created in the code behind in Listing 9. If the server sends the expected response, the requested ID, title, and description are placed into the value properties of the input control objects by this function. If the task is not found, the user is notified via a JavaScript alert. This method will then contact the server and run the implementation for DeleteTask server-side.
Remember that the server will return the updated collection when an item is deleted from the list. With the collection returned from the server, you do not need to write any additional code to finish this process-all you need to do is to display the task information to the user.
This will find the task and display the values in the input controls on the page. Finally, the method sets focus to the title control to make editing the task easy for the user. Now when you run the page you will see an edit link and a delete link.
If you click the delete link, the task item is successfully deleted from the list and the page is updated. If you click on the edit link, an input box will appear with the task information populated in the input controls.
The Save and Close buttons are not yet implemented, so clicking on those buttons at this time will result in JavaScript errors. Now you must implement the behavior that will send changes to the server to update the collection store. The following instructions will direct you to implement the Save and Close buttons in the task editor. The following code will implement some of this logic as the Save method is concerned with saving task data whether or not it is a new task or an update to a task.
Adding the UpdateTask method, implemented in Listing 11 , requires the task ID, the update title value, and the updated description value as arguments. Once the desired task is located in the collection the updates are made to the title and description. If the task is found the method returns true, if the task is not in the list the method returns false. Adding the EditTask method requires the task ID, title, and description as arguments.
Please notice that I put the call to System. Sleep in this method simply for demonstration purposes. Calling the Sleep method will force the application to wait for five seconds before continuing on with its processing.
This simulates a long server-side transaction and shows how the browser can deal with that type of latency. Finally, the data received by the page is passed to the Task object to update the task.
The AddTask method creates a new task object from the passed in title and description and then adds the new object to the task collection. Remember that the Save button persists task information on the server whether or not a task is new or recently edited. The order of business is to decide if the task is new or if the user clicked the edit link. When the edit link is clicked the task information is queried on the server and the values are filled in the input controls. The EditTask method on the server is then called, passing in the task ID and the updated title and description.
If the page determines the task is new, it calls the AddTask method on the server. The callback methods hide the status message when the server operation is complete. If everything went as planned, the status message is hidden and the browser is directed to display the updated task collection to the user.
Now when the user clicks the Edit button the task editor will appear. When they click the Save button, a status message appears at the bottom of the browser window which will persist until the client hears back from the server indicating the process is complete.
Figure 5 shows how the status message will appear at the bottom of the browser window. The application can now display the tasks to the user and allow the user to edit and delete tasks. The system is missing one last feature. The next section will grant the user the ability to add a new task to the list. Adding the add task feature from here is easy. First you want to update the HTML document.
Return to default. The HTML requires adding a link to the page that will tell the application you are creating a new task and then display the task editor to the user. Place the new line of code shown in the below snippet between these two lines.
The ClearTaskInput method will clear the controls in the task editor, priming the system for a new task. Now that you have had an opportunity to use the Ajax.
When a response is returned from the server you have a response object filled with the returned data. At no time did you have to parse through XML markup or manually poll the server for ready states. NET Framework saves developers time and simplifies the process of creating Ajax applications. My Subscriber Account Advertise Write.
Training Home State of. Staffing Home Looking for Staff? Looking for Work? Contact Us. Dark Kimbie. Published in:. What Is Ajax? How Does Ajax Work? Even with a few extra server calls you are still sending less data across the wire than you would with traditional postbacks which often include full ViewState information.
Call Backs Ajax will request a service from the server and wait for a response. Implications of N-Tiered Development Some of the traditional lines of n-tier application architecture may blur when you use Ajax.
What Is the Ajax. A Basic Example The following steps will guide you through creating your first Ajax. Figure 1: The Hello World application displays a message to the user. Step 2: Add the HttpHandler in web.
The controller gets that data from the data storage medium 3 and from the data model that serializes that data as JSON 4 and sends the response back to the HTML page 5. If you look at Figure 2 , you can see both the JavaScript and C code on the client and the server that corresponds to each of the numbers on Figure 1. Don't worry too much about the code in Figure 2 , you're going to learn how to build it in this article. Although the XMLHttpRequest object is the basis for all Ajax calls, there are actually a few different ways you can use this object.
Table 1 provides a list of the common methods in use today. If you're unfamiliar with the terms callbacks and promises, the two sections that follow provide you with a definition and some links to learn more about each.
A callback is the object reference the name of a function that's passed to another function. That function can then determine if and when to invoke callback that function. It may call that function after some variable changes state, or maybe after some task is performed.
A promise is the result of the completion of an asynchronous operation. The operation may succeed, fail, or be cancelled. Whatever the result, the promise allows access to the result and any data returned by the operation. I suggest you follow along step-by-step with this article to build a C.
For this article, I'm going to use the technologies listed below. If you wish to follow along, download these tools and install them on your computer. At the time of the writing of this article, these tools can be retrieved from the following locations. To retrieve data from an Ajax call, you must have a Web server running that has a series of endpoints methods to call. This Web server can be created with a variety of tools, including Node and.
NET 5. I'm going to use. NET 5 in this series of articles, but Node works just as well. In this section of this article, you'll create the.
Open an instance of VS Code and open a terminal window. Navigate to your normal development folder. Create a. Your VS Code will look like that shown in Figure 3. At the bottom right-hand corner of VS Code, a dialog appears Figure 4 asking you to add some required assets. If, for some reason, you don't see this dialog, exit VS Code and restart it. In the Security Warning dialog that appears next, also answer Yes. Once the browser appears, it comes up with a error page.
After hitting enter, you should see a string that looks like Figure 5. You can download a. To use the Entity Framework in the. NET application, you need to add a package to your project. Ensure that the terminal prompt is in your WebAPI project folder and type in the following command. Product table. Into this new file, add the code shown in Listing 1.
To retrieve and modify data in the SalesLT. Product table through the Product class you need an instance of a DbContext class. Add the code shown in Listing 2 to this file. You need a connection string for the DbContext object to work. It's a best practice to place your connection strings in the appSettings.
Open the appSettings. Set the value of this new JSON object to the code shown below. Note that I had to break the connection string across multiple lines to format it for the printed page. When you type in your connection string, ensure that it's all is on a single line. When using a. Add some packages and configuration code to help make this magic happen.
The recommended package to use these days is the one contained in the System. Json package. The JavaScript code you wrote in your node or. These are two completely different domains. To use CORS, you need to add this package into your project. Go back to the terminal window and type in the following command. Now that you've added two new packages, let's use them. Open the Startup. Locate the ConfigureServices method and add the code shown in bold in Listing 3. This code informs this project that you want to allow CORS to be used.
It also sets the JSON converter to automatically convert and property names that are in camel case to Pascal case and vice versa. The next lines inject an instance of the AdventureWorksLTDbContext class you created earlier and passes in an options object that is loaded with the connection string you stored in the appSettings.
Locate the Configure method and add the lines of code shown in bold below. You're most likely going to be building several controllers, so it's best to create a base class that all your controllers can inherit from. Microsoft supplies the ControllerBase class that all controllers should inherit from.
Create your own class like the one shown in Listing 4 that inherits from ControllerBase. Then make all your classes inherit from this BaseApiController class. Adding your own base controller class allows you to add code that all controllers can use.
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