How can one avoid PostBack without relying on JavaScript?

Question

How can one avoid PostBack without relying on JavaScript?

I have an asp button in default.aspx:

<asp:Button ID="Button1" runat="server" Text="Button" />

Additionally, there is a procedure in default.aspx.vb:

Protected Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
    Panel1.Controls.Add(New LiteralControl(Date.Now))
End Sub

The instructor has presented me with a challenge to achieve the same function (displaying the current date upon clicking the button), without causing a postback and without utilizing any JavaScript code. While I could choose to implement a JavaScript solution using OnClientClick="return false", I want to explore alternative approaches.

javascript asp.net vb.net

Answer 1

Answer №1

Check out The Benefits of Using ASP.Net on the Client Side

It's not possible. The default action of a Button (input type=submit) is to submit/post the form to the URL specified in the form's action attribute.

To override this default behavior, you will need to include a Javascript statement return false

<asp:Button ID="btn" OnClientClick="return false" runat="server" Text="Click Me!" />

By default, ASP.Net posts the form to the same page, known as PostBack. Check the action value of the form tags in the rendered HTML in your browser, it should be the same as the page name

<input type =submit name ="btn" id="btn" 
  onclick="javascript:__doPostBack('btn','')"value ="Click Me!">

The following built-in JavaScript function accomplishes this:

<script>
                   function __doPostBack(eventTarget, eventArgument) {
                       document.Form1.__EVENTTARGET.value = eventTarget;
                       document.Form1.__EVENTARGUMENT.value = eventArgument;
                       document.Form1.submit();
                   }
</script>

Your page will automatically add the following fields so that the server side knows which event needs to be triggered. You can easily access them using request parameters like Request.Params["__EVENTTARGET"]

<input type =hidden name ="__EVENTTARGET" value ="">
<input type =hidden name ="__EVENTARGUMENT" value ="">

Answer 2

Check out The Benefits of Using ASP.Net on the Client Side

It's not possible. The default action of a Button (input type=submit) is to submit/post the form to the URL specified in the form's action attribute.

To override this default behavior, you will need to include a Javascript statement return false

<asp:Button ID="btn" OnClientClick="return false" runat="server" Text="Click Me!" />

By default, ASP.Net posts the form to the same page, known as PostBack. Check the action value of the form tags in the rendered HTML in your browser, it should be the same as the page name

<input type =submit name ="btn" id="btn" 
  onclick="javascript:__doPostBack('btn','')"value ="Click Me!">

The following built-in JavaScript function accomplishes this:

<script>
                   function __doPostBack(eventTarget, eventArgument) {
                       document.Form1.__EVENTTARGET.value = eventTarget;
                       document.Form1.__EVENTARGUMENT.value = eventArgument;
                       document.Form1.submit();
                   }
</script>

Your page will automatically add the following fields so that the server side knows which event needs to be triggered. You can easily access them using request parameters like Request.Params["__EVENTTARGET"]

<input type =hidden name ="__EVENTTARGET" value ="">
<input type =hidden name ="__EVENTARGUMENT" value ="">

How can one avoid PostBack without relying on JavaScript?

Answer №1

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