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Unable to display report viewer in ASP.Net MVC application

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Aaron asked on 30 Mar 2012, 03:13 AM

I'm attempting to use the report viewer ASP.Net control in an ASP.Net MVC application. When I include the viewer control on a page I get the folwwoing error.

The Controls collection cannot be modified because the control contains code blocks (i.e. <% ... %>).

I'm using the simplest possible view to display the report viewer and which I copied from a Telerik sample that demonstrates how to use the report viewer in an ASP.Net MVC application (the sample does not run).

<%@ Page Language="C#" MasterPageFile="~/Views/Shared/Site.Master" Inherits="System.Web.Mvc.ViewPage" %>

<%@ Register Assembly="Telerik.ReportViewer.WebForms, Version=6.0.12.302, Culture=neutral, PublicKeyToken=a9d7983dfcc261be" Namespace="Telerik.ReportViewer.WebForms" TagPrefix="telerik" %>

<asp:Content ID="Content1" ContentPlaceHolderID="TitleContent" runat="server">

Reports

</asp:Content>

<asp:Content ID="Content2" ContentPlaceHolderID="MainContent" runat="server">

<h2>Test Report</h2>

<script runat="server">

public override void VerifyRenderingInServerForm(Control control)

{

// to avoid the server form (<form runat="server">) requirement

}

protected override void OnLoad(EventArgs e)

{

base.OnLoad(e);

// bind the report viewer

ReportViewer1.Report = new Mine.Web.UI.Reports.HelloWorld();

}

</script>

<telerik:ReportViewer runat="server" ID="ReportViewer1" />

</asp:Content>

The error is being caused by the line below in my Site.Master file. Removing that line allows the report viewer to display but breaks the application because now the stylesheets needed for the Telerik ASP.NEt MVC controls aren't being loaded.

<%: Html.Telerik().StyleSheetRegistrar().DefaultGroup(group => group.Add("telerik.common.css").Add("telerik.metro.css").Combined(true).Compress(true)) %>

This seems like a really common scenario? Surely I'm not the first person to try and use the report viewer and the MVC extensions at the same time?

5 Answers, 1 is accepted

answered on 02 Apr 2012, 04:08 PM

Hello Aaron,

This is a common problem not only related to a particular product, but to the ASP.NET MVC framework in general. There is a quite simple solution for the problem. First instead of <%= use <%# - this changes the code block from a Response.Write code block to a databinding expression. Since <%# ... %> databinding expressions aren't code blocks, the CLR won't complain. Then in the code for the master page add the following:

<script runat="server">

protected void Page_Load(object sender, EventArgs e)

{

this.DataBind();

}

</script>

(or add it to the code-behind of the master page).

I hope this helps.

Kind regards,
IvanY
the Telerik team

NEW in Q1'12: Telerik Report Designer (Beta) for ad-hoc report creation. Download as part of Telerik Reporting Q1 2012. For questions and feedback, use the new Telerik Report Designer Forum.

answered on 03 Apr 2012, 12:40 AM

Hi Ivan,

I did see that suggestion in other forums posts and had already tried it. And while using <%# .. %> does stop the error from occurring it also breaks the Telerik style sheet registration statement which means I don't get the Telerik stylesheets loading on pages anymore.

The full block I am using on my Site.Master is:

<head runat="server">

<title><asp:ContentPlaceHolder ID="TitleContent" runat="server" /></title>

<link href="../../Content/bootstrap.min.css" rel="stylesheet" type="text/css" />

<link href="../../Content/bootstrap-responsive.min.css" rel="stylesheet" type="text/css" />

<link href="../../Content/Site.css" rel="stylesheet" type="text/css" />

<%# Html.Telerik().StyleSheetRegistrar().DefaultGroup(group => group.Add("telerik.common.css").Add("telerik.metro.css").Combined(true).Compress(true)) %>

</head>

Changing the <%# .. %> back to <%: .. %> results in the stylesheets loading but causes the error when using the report viewer.

Perhaps I need to use the Html.Telerik().StyleSheetRegistrar() call differently?

Thanks,
Aaron

answered on 03 Apr 2012, 01:15 AM

I finally fixed it by using the code block below.

<head>

<title><asp:ContentPlaceHolder ID="TitleContent" runat="server" /></title>

<link href="<%= Url.Content("~/Content/bootstrap.min.css") %>" rel="stylesheet" type="text/css" />

<link href="<%= Url.Content("~/Content/bootstrap-responsive.min.css") %>" rel="stylesheet" type="text/css" />

<link href="<%= Url.Content("~/Content/Site.css") %>" rel="stylesheet" type="text/css" />

<%: Html.Telerik().StyleSheetRegistrar().DefaultGroup(group => group.Add("telerik.common.css").Add("telerik.metro.css").Combined(true).Compress(true)) %>

</head>

I'm not sure why the default MVC template sets runat="server" on the head element but since it does this will probably trip up other people as well.