CODEWITHSUNDEEP
asp.net
Razor
Razor

Reputation: 17508

How can I inject a piece of VB.NET code in to an ASPX page and have it execute?

The following piece of code executes as expected when placed in a user control or ASPX page.

<script type="text/javascript">

    (function() {

        if (someCondition) {            
            if (<%=MyObject.IsActiveSession.ToString().ToLower() %>) {
            <% If (MyObject.IsLoggedIn) Then %>
                // Do some fancy stuff
            <% End If %>
            } 
        }
    })();
</script>

It renders as you would expect when the page executes.

Is there any way I can inject this code in the page dynamically and have it execute?

I tried using a Literal Web Control and surprise surprise, it output the code literally :)

Upvotes: 0

Views: 353

Answers (2)

Abdul Munim
Abdul Munim

Reputation: 19217

There aren't much friendly Template Engines available for .NET atleast for the community. I ran into the same trouble last year where I had to keep some portion of my codes maintained by the clients as they wanted to format their own way of text formatting.

The easiest way I found without getting into any 3rd party libraries is using the power of ASPX rendering engine as your template code, but in a manageable way.

Create an ASPX page for your template for instance ~\Templates\LoggedInBlock.aspx and as content:

<script type="text/javascript">

    (function() {

        if (someCondition) {            
            if (<%=MyObject.IsActiveSession.ToString().ToLower() %>) {
            <% If (MyObject.IsLoggedIn) Then %>
                // Do some fancy stuff
            <% End If %>
            } 
        }
    })();
</script>

Now create a template renderer generic handler, for instance ~\TemplateRenderer.ashx

Imports System
Imports System.Collections.Generic
Imports System.IO
Imports System.Linq
Imports System.Web

Namespace TestApp1
    Public Class TemplateRenderer
        Implements IHttpHandler
        Private Function GetContent(context As HttpContext, tempateName As String) As String
            Using textWriter = New StringWriter()
                context.Server.Execute(String.Format("~/Templates/{0}", tempateName), textWriter)
                Return textWriter.ToString()
            End Using
        End Function

        Public Sub ProcessRequest(context As HttpContext)
            context.Response.Write(GetContent(context, context.Request.QueryString("template")))
        End Sub

        Public ReadOnly Property IsReusable() As Boolean
            Get
                Return False
            End Get
        End Property
    End Class
End Namespace

Now from where you want your dynamic code block to append as it just another small piece of ASPX page:

Protected Sub Page_Load(sender As Object, e As EventArgs)
    Dim templateName = "LoggedInBlock.aspx"
    Using textWriter = New StringWriter()
        Server.Execute(String.Format("~/TemplateRenderer.ashx?template={0}", templateName), textWriter)
        dynamicCodeInjectPanel.InnerHtml = textWriter.ToString()
    End Using
End Sub

Courtesy: http://converter.telerik.com/ used to convert from C# to VB code.

Upvotes: 1

Adam Tuliper
Adam Tuliper

Reputation: 30152

Not in any manner I would consider very clean, although I believe it is possible using dynamic compilation in the codedom

See: http://www.codeproject.com/KB/cs/smarttemplateengine.aspx

Upvotes: 0

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