How to Use __doPostBack() for Asynchronous Postbacks in ASP.NET with Vanilla JavaScript?

Use native JavaScript to implement __doPostBack() asynchronous postback in ASP.NET

This article will guide you on how to implement asynchronous postback in ASP.NET using native JavaScript and __doPostBack() functions.

The steps are as follows:

1. Assign ID to button: Assign an ID to the button that triggers the postback, such as "btnSave".

2. Button click event: Add an onclick event to the button, which calls the __doPostBack() function. The first parameter is the ID of the button, and the second parameter is optional additional data. For example:

<code class="language-javascript">//  在你的HTML中，按钮的onclick事件应该类似这样：
<asp:Button ID="btnSave" runat="server" Text="Save" OnClientClick="SaveWithParameter('someData')" /></code>

3. Define the SaveWithParameter function: This function receives additional parameters as input and is called with the ID of the button as the first parameter and the additional parameter as the second parameter __doPostBack().

<code class="language-javascript">function SaveWithParameter(parameter) {
  __doPostBack('btnSave', parameter);
}</code>

4. Server-side code: In your server-side code file (e.g. .aspx.cs), handle the request in the Page_Load method. Use Request["__EVENTARGUMENT"] to retrieve additional parameters. An example is as follows:

<code class="language-csharp">protected void Page_Load(object sender, EventArgs e)
{
  string parameter = Request["__EVENTARGUMENT"]; // 获取附加参数
  // Request["__EVENTTARGET"]; // 获取按钮ID  btnSave
  // ... 使用参数进行处理 ...
}</code>

Through the above steps, you can use __doPostBack() to easily implement asynchronous postback in ASP.NET and pass custom data to the server. This provides a clean way to handle client-side events and update server-side data without requiring a full page refresh.

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