在VB.NET代码后面动态添加JS块

Question

I am working on a system that administers a number of pages to end users for data entry. There is a need to prevent the back button (I know, not ideal, but that is the requirement), but to disable this 'block' when viewing the pages in test mode.

I have the necessary JS and it works for what we need, but I'm having issues adding the code dynamically to the page so that it fires.

What do I mean by this? Well, I can get the code block added dynamically so it looks exactly as it should, but the code doesn't work. If I copy and paste the text and manually add it to the aspx page (so not using code behind to do it), it works fine.

Here's the JS to work-around the back button click:

> <script type="text/javascript">
>       function preventBack(){window.history.forward();} setTimeout("preventBack()", 0); window.onunload=function(){null};
>     </script>

In my aspx.vb code behind file I have the following:

If Not TestMode Then
  ' add JS
End If

I have tried adding the JS in the following ways - none of which seem to have worked:

1. Page.RegisterClientScriptBlock("preventBack", "<script type=""text/javascript"">function preventBack(){window.history.forward();} setTimeout(""preventBack()"", 0); window.onunload=function(){null};</script>")

2. Dim scriptText As New StringBuilder

    scriptText.Append("<script type='text/javascript'>") scriptText.Append("function preventBack(){") scriptText.Append(" window.history.forward();} ") scriptText.Append("setTimeout('preventBack()', 0); ") scriptText.Append("window.onunload=function(){null};") scriptText.Append("</script>") ClientScript.RegisterClientScriptBlock(Page.GetType, "noback", scriptText.ToString, False) 

3. Dim lit As New Literal

    lit.Text = "<script type='text/javascript' src='JS/noBack.js'>" '"<script type='text/javascript'>function preventBack(){window.history.forward();} setTimeout('preventBack()', 0); window.onunload=function(){null};</script>" Head1.Controls.Add(lit) 

4. Dim gc As New HtmlGenericControl

    gc.TagName = "script" gc.Attributes.Add("type", "javascript") gc.Attributes.Add("src", "JS/noBack.js") Head1.Controls.Add(gc) 

5. ClientScript.RegisterClientScriptBlock(Me.GetType(), "MyScript", "JS/noBack.js", True)

Where the noBackJS file contains the JS code mentioned above.

As I said, the actually code is written to the HTML on the page when rendered, but doesn't work/fire at all. Clearly I'm missing something here, but can't for the life of me work out what it is, can anyone help please?

Thx.

Answer 1

try this:

Dim jScript As String = "<script>alert('')</script>"
Page.ClientScript.RegisterStartupScript(Me.GetType(), "Registered Script", jScript, False)

Answer 2

您可以使用eval() ，例如：

eval($("#mytextbox").val())