Raj Kaimal : .NET

Rendering an RDLC directly to the Response stream in ASP.NET MVC

rajbk — Wed, 25 Nov 2009 07:21:59 GMT

The following post shows you how to render an RDLC (Client Report Definition File) in a MVC project. For this tutorial, I am using VS 2008 with MVC 2 Beta. I will also be using the priceless Northwind database and the report will contain a list of customers in the Northwind database.

A sample project zip file is provided at the bottom of this post.

We start off by creating an ASP.NET MVC 2 Empty Web Application.

Add a new ADO.NET entity model and choose the option to “Generate from the database”.

Choose the connection string to use

Choose the database objects (Customers for our scenario) and hit finish. We see that a new entity data model has been created in the Models directory.

Create a folder called Content and a subfolder called Reports and add an RDLC into this folder. I hate working with Datasets and hence will not be using the “Report Wizard”. We choose the “Report” template instead.

Create a method that returns all the customers in the database through a Customer partial class and add this in the Model folder.

using System;
using System.Linq;
using System.Collections.Generic;

namespace RDLCRendering.Models
{
    public partial class Customers
    {
        public static List<Customers> GetAllCustomers() {
            var entities = new NorthwindEntities();
            var x = from c in entities.Customers
                    select c;
            return x.ToList();
        }
    }
}

Open the RDLC. Your UI should look like so (If you don’t see “Website Data Sources”, click on Data –> Show Data Sources):

Design your report by adding a table from the toolbox and dragging and dropping fields from the Website Data Sources (reference).

We will now construct our basic MVC web application. The app will have a home screen and a link to view the PDF report of Northwind customers.
Lets start by adding a Home controller

We add the following code in our HomeController class

namespace RDLCRendering.Controllers
{
    public class HomeController : Controller
    {
        public ActionResult Index()
        {
            string welcomeMessage = "Welcome to Northwind Traders. Enjoy the view!";
            return View((object)welcomeMessage);
        }
    }
}

Right click on the "Index()” method and select “Add View”.

Open the Index view and add code to display the string returned and also add a link for the report in the view like so:

<%@ Page Language="C#" Inherits="System.Web.Mvc.ViewPage<string>" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" 
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <title>Index</title>
</head>
<body>
    <div>
        <h2>
            <%=Html.Encode(Model) %></h2>
            
            <%=Html.ActionLink("Customers Report (PDF)", "DetailsReport", "Customers") %>
    </div>
</body>
</html>

Run the application. You should see a UI similar to the one below:

If you click on the link you will get a “The resource cannot be found.” error. This is because our Html.Action link refers to a method called “DetailsReport” in a CustomersController which does not exist yet.
Note that we are using the ActionLink overload(linkText, actionName, controllerName).

First add a reference to Microsoft.ReportViewer.WebForms in your project.

Add a CustomerController class and add a DetailsReport method like so:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Mvc;
using System.Web.Mvc.Ajax;
using Microsoft.Reporting.WebForms;
using RDLCRendering.Models;

namespace RDLCRendering.Controllers
{
    public class CustomersController : Controller
    {
        public ActionResult Index()
        {
            return View();
        }

        public ActionResult DetailsReport()
        {
            LocalReport localReport = new LocalReport();
            localReport.ReportPath = Server.MapPath("~/Content/Reports/CustomerReport.rdlc");
            ReportDataSource reportDataSource = new ReportDataSource("Customers", Customers.GetAllCustomers());

            localReport.DataSources.Add(reportDataSource);
            string reportType = "PDF";
            string mimeType;
            string encoding;
            string fileNameExtension;

            //The DeviceInfo settings should be changed based on the reportType
            //http://msdn2.microsoft.com/en-us/library/ms155397.aspx
            string deviceInfo =
            "<DeviceInfo>" +
            "  <OutputFormat>PDF</OutputFormat>" +
            "  <PageWidth>8.5in</PageWidth>" +
            "  <PageHeight>11in</PageHeight>" +
            "  <MarginTop>0.5in</MarginTop>" +
            "  <MarginLeft>1in</MarginLeft>" +
            "  <MarginRight>1in</MarginRight>" +
            "  <MarginBottom>0.5in</MarginBottom>" +
            "</DeviceInfo>";

            Warning[] warnings;
            string[] streams;
            byte[] renderedBytes;

            //Render the report
            renderedBytes = localReport.Render(
                reportType,
                deviceInfo,
                out mimeType,
                out encoding,
                out fileNameExtension,
                out streams,
                out warnings);
            //Response.AddHeader("content-disposition", "attachment; filename=NorthWindCustomers." + fileNameExtension);
            return File(renderedBytes, mimeType);
        }
    }
}

This method will create an instance of the LocalReport class, set the Report path property, add a ReportDataSource which points to the GetAllCustomers method we defined earlier, set the report output type and page dimensions, calls the render method and invokes the File method on the Controller class. This method return a FileContentResult which sends the contents of a binary file to the response stream.

Run the page and click on the link. You should see the PDF report like so:

If you wish to prompt the user to download the PDF file, uncomment the “content-disposition” line and recompile.

Download Sample MVC Beta 2 project

The Windows Azure Cloud Air Handling Unit

rajbk — Wed, 25 Nov 2009 00:35:17 GMT

Great technical video presented by Patrick Yantz showing the Azure Cloud Air handling unit. Patrick is a Datacenter Systems Architecture Manager at Microsoft.

Version 1

Version 2

Sun Microsystems has something similar – The Sun Modular DataCenter

VS 2010 Beta 2 Installation instructions

rajbk — Tue, 20 Oct 2009 01:39:00 GMT

For those of you that have VS 2010 Beta 1 installed.

http://go.microsoft.com/fwlink/?LinkID=166199

http://go.microsoft.com/fwlink/?LinkID=167718 (addendum)

Other observations:

I was prompted for my VS 2010 Beta 1 media when uninstalling it so have your iso or media ready.

VS 2010 Beta 2 prompted for a OS restart during installation.

See announcement for more details.

XMLSerializer and invalid XML

rajbk — Mon, 05 Oct 2009 01:29:08 GMT

A user had pasted some text from powerpoint into a textarea in one of our web apps which was eventually serialized into XML. Upon trying to de-serialize the XML, the web server threw the exception below:

System.InvalidOperationException: There is an error in XML document (1, 50). ---> System.Xml.XmlException: '♂', hexadecimal value 0x0B, is an invalid character. Line 1, position 50.

The XML that was about to be de-serialized looked like something this:

<?xml version="1.0" encoding="utf-16"?>
<string>Quick&#xB;Brown
Fox
</string>

The code used to de-serialze the xml is shown below:

    public static T DeSerializeObject<T>(string xml)

    {

        using (System.IO.StringReader sr = new System.IO.StringReader(xml))

        {

            XmlSerializer serializer = new XmlSerializer(typeof(T));

            return (T)serializer.Deserialize(sr);

        }

    }

As seen from the exception above, the de-serializer was complaining about the invalid character - .

The PowerPoint slide that text was being pasted from looked something like this:

The user had used the Shift-Enter key combination to force a line break between text in a bullet. So “Brown” is started on a new line for the same bullet as “Quick”.

By selecting all the text on the slide and pasting it into a hex editor, we see the standard hex values for carriage return and line feed – 0x0D 0x0A between “Brown” and “Fox”. But we see 0x0B was generated for the new line between “Quick” and “Brown”. 0x0B in ASCII stands for a vertical line tab which is an invalid character in XML.

The code used to serialize the string is shown below:

    private static string SerializeObject<T>(T source)

    {

        var serializer = new XmlSerializer(typeof(T));

        using (var sw = new System.IO.StringWriter())

        using (var writer = new XmlTextWriter(sw))

        {

            serializer.Serialize(writer, source);

            return sw.ToString();

        }

    }

The problem with this code is that the XmlTextWriter class which inherits from XmlWriter, does not, on its own, validate each character before serializing it.

The recommended way to serialize is to use the static XmlWriter.Create method. The method has overloads where you specify an XmlWriterSettings class. If you do not specify one, the default values for the XmlWriterSettings class is used. One of the properties of this class is the XmlWriterSettings.CheckCharacters Property which is set to true by default. This property ensures that the XmlWriter instance created by the .Create method will perform character checking. By implementing the .Create* method in our code, we ensure that the serializer will throw an exception if it encounters invalid XML.

We, therefore, can rewrite our serializer class like so:

    private static string SerializeObject<T>(T source)

    {

        var serializer = new XmlSerializer(typeof(T));

        using (var sw = new System.IO.StringWriter())

        using (var writer = XmlWriter.Create(sw))

        {

            serializer.Serialize(writer, source);

            return sw.ToString();

        }

    }

* The writer created in this case is of type System.Xml.XmlWellFormedWriter. It will vary based on the .Create overload used.

FormView Binding Gotcha

rajbk — Mon, 03 Aug 2009 06:17:00 GMT

Version: ASP.NET 3.5 SP1

This post describes two gotchas with the FormView control when binding:
1) When performing two way databinding, Null values and Nullables get changed to string.Empty in the FormView.
2) Two way binding is not supported for nested controls.

When performing two way databinding, Null values and Nullables get changed to string.Empty in the FormView.
The way the FormView control handles null values has caused me some grief :-(

Consider a FormView bound to an ObjectDataSource like so:

<asp:FormView ID="FormView1" runat="server" DataSourceID="ObjectDataSource1" DefaultMode="Edit">
    <EditItemTemplate>
        FirstName:
        <asp:TextBox ID="FirstNameTextBox" runat="server" Text='<%# Bind("FirstName") %>' />
        <br />
        LastName:
        <asp:TextBox ID="LastNameTextBox" runat="server" Text='<%# Bind("LastName") %>' />
        <br />
        <asp:LinkButton ID="UpdateButton" runat="server" CausesValidation="True" CommandName="Update"
            Text="Update" />
    </EditItemTemplate>
</asp:FormView>

<asp:ObjectDataSource ID="ObjectDataSource1" runat="server" DataObjectTypeName="Employee"
        OldValuesParameterFormatString="original_{0}" SelectMethod="GetEmployee" TypeName="EmployeeWrapper"
        ConflictDetection="CompareAllValues" UpdateMethod="SetEmployee"></asp:ObjectDataSource>

The Employee object returned by the ObjectDataSource has LastName set to null like so:

[DataObjectMethod(DataObjectMethodType.Select)]
public Employee GetEmployee()
{
    return new Employee()
    {
        FirstName = "Tom",
        LastName = null
    };
}

Click the Update button on the FormView without changing any properties. In the Form ItemUpdating event, we see that both the OldValues and NewValues have the LastName property set to string.Empty.

(OldValue according to FormView)
FirstName : Tom
LastName :
 
(NewValue according to FormView)
FirstName : Tom
LastName :

On the other hand, if we try the same thing with the DetailsView control, the LastName will still be “null” on update.

This FormView behavior can be problematic when we we need the original object and the modified object to perform an update with conflict detection (see LINQ to SQL example below). Note that ConflictDetection is set to CompareAllValues in the ObjectDataSource.

<asp:ObjectDataSource ID="ObjectDataSource1" runat="server" ConflictDetection="CompareAllValues"
    DataObjectTypeName="Customer" OldValuesParameterFormatString="original_{0}" SelectMethod="GetCustomer"
    TypeName="CustomerWrapper" UpdateMethod="SetCustomer">
    <UpdateParameters>
        <asp:Parameter Name="customer" Type="Object" />
        <asp:Parameter Name="original_customer" Type="Object" />
    </UpdateParameters>
</asp:ObjectDataSource>

public void SetCustomer(Customer customer, Customer original_customer)
{
    DataClassesDataContext context = new DataClassesDataContext();
    context.Customers.Attach(customer, original_customer);
    context.SubmitChanges();
}

In brief, LINQ to SQL compares the original value and new value and generates SQL code to update the original object. Since the original object was modified by the FormView, it will never be found by SQL and no update will occur!

While there are other techniques you can use with Linq to SQL to avoid the issue above, the point of this post is to show how the FormView handles null values.

The workaround is to subscribe to the FormView ItemUpdating event and look for string.empty NewValues and set those to null instead.

protected void FormView2_ItemUpdating(object sender, FormViewUpdateEventArgs e)
{
    if (e.NewValues["LastName"].Equals(string.Empty))
    {
        e.NewValues["LastName"] = null;

    }
}

In addition, to keep the OldValues unchanged (if you need it for concurrency purposes), set the DataKeyNames property of the FormView to the properties of the object like so:

<asp:FormView ID="FormView2" runat="server" DataSourceID="ObjectDataSource1" OnItemUpdating="FormView2_ItemUpdating"
        DefaultMode="Edit" DataKeyNames="LastName, FirstName">

When the Update button is clicked this time, the null values are retained.

(OldValue according to FormView)
FirstName : Tom
LastName : null
 
(NewValue according to FormView)
FirstName : Tom
LastName : null

Two way binding is not supported for nested controls – AFAIK, this is by design.
See an example below:

<EditItemTemplate>
    <asp:UpdatePanel runat="server" ID="up1">
        <ContentTemplate>
            FirstName:
            <asp:TextBox ID="FirstNameTextBox" runat="server" Text='<%# Bind("FirstName") %>' />
        </ContentTemplate>
    </asp:UpdatePanel>
    LastName:
    <asp:TextBox ID="LastNameTextBox" runat="server" Text='<%# Bind("LastName") %>' />
    <br />
    <asp:LinkButton ID="UpdateButton" runat="server" CausesValidation="True" CommandName="Update"
        Text="Update" />
</EditItemTemplate>

Here we have a TextBox inside an UpdatePanel inside the EditItemTemplate. Since two way binding is not supported for the FirstNameTextBox, the special code for extracting values is not generated resulting in null being sent back for the FirstName property.

To work around this, you will need to subscribe to the ItemUpdating event and extract the values yourself:

protected void FormView2_ItemUpdating(object sender, FormViewUpdateEventArgs e)
{
    TextBox FirstNameTextBox = (TextBox)FormView2.FindControl("FirstNameTextBox");
    e.NewValues["FirstName"] = FirstNameTextBox.Text;
}

Visibility of controls in a FormView.
Setting Visibility of a control inside a FormView does not work - the TextBox control goes back to visible on update.

protected void Page_Load(object sender, EventArgs e)
{
    FormView1.FindControl("FirstNameTextBox").Visible = false;
}

Do it in the DataBound event instead:

protected void FormView2_DataBound(object sender, EventArgs e)
{
    FormView1.FindControl("FirstNameTextBox").Visible = false;
}

If you have better ideas on any of the workarounds above, please post a comment or link. Thanks.

The .NET Framework 3.5 Commonly Used Types and Namespaces poster

rajbk — Sun, 04 Nov 2007 04:39:00 GMT

Paul Andrew has posted a link to the .NET framework 3.5 commonly Used Types and Namespaces poster - cool stuff!

Download it here.

Daniel Moth also has a good older post on the .NET 3.5 bits

.NET Framework Libraries Source Code - License - MS-RL

rajbk — Wed, 03 Oct 2007 18:17:00 GMT

When I first read Scott's post, I missed the Microsoft Reference License (Ms-RL) which the .net Framework libraries is released under.

The key thing to remember is this:

"Reference use" means use of the software within your company as a reference, in read only form, for the sole purposes of debugging your products, maintaining your products, or enhancing the interoperability of your products with the software, and specifically excludes the right to distribute the software outside of your company.

.NET Framework Libraries Source Code

rajbk — Wed, 03 Oct 2007 16:50:00 GMT

Scott just announced that his team will be releasing the souce code to the .NET base class libraries, ASP.net, Windows Forms and WPF!

The big advantage to this is that when you are stepping through the code, you no longer see the horrible "[External Code]' in your call stack. You are taken right to the source code! This really really helps in understanding how the internals of the classes work.

Wonder what I am going to do with reflector...hmm...

Read more at Scotts' blog

PS: The source code is being released under Ms-RL which means that I can view but I'm not allowed to copy and paste the source code.

Microsoft Silverlight

rajbk — Tue, 01 May 2007 21:07:00 GMT

I am at MIX 2007 and writing a quick post inbetween classes.

Very excited about what I have seen so far regarding Sliverlight. Some things I like:

Manipulate the DOM using Silverlight.
Write in C# - which is way better than Actionscript ;-)
Create custom Silverlight controls
Light plugin that installs really fast!!!
Silverlight^TM Streaming by Windows Live^TM rocks!

My only concern is how can we guarantee that the client will install the plugin? There are organizations out there that have locked their active directory using group policies. How can we convince the IT department (those that are concerned about security) to deploy this plugin in across the directory? In addition, public access terminals are also generally locked down which prevents the user from viewing a page developed using Silverlight. IMHO, MS should put the word out there about why this is a safe plugin to install.

Page.IsValid and Validate

rajbk — Thu, 15 Mar 2007 19:16:00 GMT

ASP.net ships with a couple of validator controls that allow you to determine whether the value of the input controls they are validating is valid.

Here is a simple example of a TextBox control with a RequiredFieldValidator attached and a Button control.

Note that all controls belong to the same ValidationGroup - a new feature of ASP.net 2.0. With JavaScript turned on, when a user clicks the button, they will see an error message displayed next to the control being validated if they fail to fill in the TextBox. (One could also use a ValidationSummary control)

With JavaScript turned off, what may not be known is that, on the server side, even though the validators fire, it is left to the developer on how to use that information.

You may think you have built a secure application but a hacker could disable JavaScript and bypass *all* your validators! This is where the Page.Validate method and more importantly, the Page.IsValid property come in.

The Validate method is fired automatically by controls that have the CausesValidation property set to true. Note that the Button control's CausesValidation property is true by default. The Validate method iterates through all enabled validation controls on the page and validates them. This event occurs after the Load event in the page lifecycle.

If the control that raised the event has a ValidationGroup specified, then only enabled validator controls that belong to the same ValidationGroup are validated by calling the Page.Validate(ValidationGroup) overload method. As mentioned previously, this is done automatically for controls that have the CausesValidation property set to true.

The Page.IsValid property tells you whether the validation succeeded or not. It can be called only after the Page.Validiate method is called. By using this property, you can add logic to your page to determine whether to proceed with the PostBack event or not. So, in addition to relying on client side validation, it is also important that you call Page.IsValid when handling the postback event. Here is what the code behind will look like:

protected void Button1_Click(object sender, EventArgs e) {
//Not required since the CausesValidation property of the Button control is true by default.
//Page.Validate("MyValidationGroup");

//Proceed only if the vaidation is successfull
if (!Page.IsValid) {
return;
}
//Insert data into SQL
}

With the ASP.net declarative programming approach, the Page.IsValid method is something easy to forget.

Since you have reached this point, here is a simple quiz ;-) In the code below, what happens when Button2 is clicked?

<asp:TextBox ID="TextBox1" runat="server" ValidationGroup="MyValidationGroup"></asp:TextBox>
<asp:RequiredFieldValidator ID="RequiredFieldValidator1" runat="server" ControlToValidate="TextBox1"
ErrorMessage="This field is required!" ValidationGroup="MyValidationGroup"></asp:RequiredFieldValidator>
<br />
<asp:Button ID="Button1" runat="server" Text="Button" ValidationGroup="MyValidationGroup" CausesValidation="true" />
<br />
<br />
<asp:TextBox ID="TextBox2" runat="server" ValidationGroup="AnotherValidationGroup"></asp:TextBox>
<asp:RequiredFieldValidator ID="RequiredFieldValidator2" runat="server" ControlToValidate="TextBox2"
ErrorMessage="This field is required!" ValidationGroup="AnotherValidationGroup"></asp:RequiredFieldValidator>
<br />
<asp:Button ID="Button2" runat="server" Text="Button" ValidationGroup="AnotherValidationGroup" OnClick="Button2_Click" />

protected void Button2_Click(object sender, EventArgs e) {
    Page.Validate("MyValidationGroup");
    if (!Page.IsValid) {
        return;
    }
    Response.Write("Button was clicked at " + DateTime.Now.ToShortTimeString());
}

EditorBrowsable - EditorBrowsableState.Never shows up in Intellisense

rajbk — Mon, 05 Mar 2007 04:05:00 GMT

I had a property in a WebControl marked as EditorBrowsableState.Never but it was still showing up in Intellisense. After googling for a long time, I found this post with a response by Linda Liu.

Speaking for C#, the EditorBrowsableAttribute attribute only influences C# IntelliSense filtering behavior if the decorated item is imported from metadata.

That's to say, you should compile the EditorBrowsableAttribute-decorated project (e.g project 1) into an assembly (.dll or .exe) and then in another project (e.g project 2) add a reference to that assembly. In project 2, you should see the attribute at work.

C# IntelliSense filtering behavior is not influenced if you are coding in project 1. What's more, if you add a project-to-project reference to project 1 in project 2, C# IntelliSense filtering behavior is not influenced when you are coding in project 2 either.

The IDE is intended to filter items from consumers of your assembly and not to filter items from yourself as you code the assembly.

Since I had a project to project reference, intellisense ignored this attribute - aargh :-(

GridView DropDownList Pager

rajbk — Mon, 14 Aug 2006 15:18:00 GMT

This post shows you how to add a custom DropDownlist pager and pager buttons to the GridView as shown below:

Unlike the behavior of the default pager buttons, these buttons get disabled instead of being hidden (depending on the state of the GridView).

IMHO, buttons that remain at the same position while paging through a resultset makes a better UI (spatial memory).

The code is pretty straightforward.

Add the following pager template to your GridView.

<PagerTemplate>Goto Page 
    <asp:DropDownList ID="ddlPageSelector" runat="server" AutoPostBack="true">
    </asp:DropDownList>
    <asp:Button Text="First" CommandName="Page" CommandArgument="First" runat="server"
        ID="btnFirst" />
    <asp:Button Text="Previous" CommandName="Page" CommandArgument="Prev" runat="server"
        ID="btnPrevious" />
    <asp:Button Text="Next" CommandName="Page" CommandArgument="Next" runat="server"
        ID="btnNext" />
    <asp:Button Text="Last" CommandName="Page" CommandArgument="Last" runat="server"
        ID="btnLast" />
</PagerTemplate> 

Add a RowCreated event handler to your GridView and add the following code:

protected void GridView1_RowCreated(object sender, GridViewRowEventArgs e) {
    if (e.Row.RowType == DataControlRowType.Pager) {
        PresentationUtils.SetPagerButtonStates(GridView1, e.Row, this);
    }
}

Finally, add the following code to your common class (PresentationUtils in my case)

public static void SetPagerButtonStates(GridView gridView, GridViewRow gvPagerRow, Page page) {
 
    int pageIndex = gridView.PageIndex;
    int pageCount = gridView.PageCount;
 
    Button btnFirst = (Button)gvPagerRow.FindControl("btnFirst");
    Button btnPrevious = (Button)gvPagerRow.FindControl("btnPrevious");
    Button btnNext = (Button)gvPagerRow.FindControl("btnNext");
    Button btnLast = (Button)gvPagerRow.FindControl("btnLast");
 
    btnFirst.Enabled = btnPrevious.Enabled = (pageIndex != 0);
    btnNext.Enabled = btnLast.Enabled = (pageIndex < (pageCount - 1));
 
    DropDownList ddlPageSelector = (DropDownList)gvPagerRow.FindControl("ddlPageSelector");
    ddlPageSelector.Items.Clear();
    for (int i = 1; i <= gridView.PageCount; i++) {
        ddlPageSelector.Items.Add(i.ToString());
    }
 
    ddlPageSelector.SelectedIndex = pageIndex;
 
    //Anonymous method (see another way to do this at the bottom)
    ddlPageSelector.SelectedIndexChanged += delegate {
        gridView.PageIndex = ddlPageSelector.SelectedIndex;
        gridView.DataBind();
    };
 
} 

AFAIK, VB.net 2.0 does not support anonymous methods. Therefore, for those of you converting this code to VB.net, you will need to add the handler manually. Go to the GridView Tasks and select "Edit templates", select the PagerTemplate and double click on the DropDownList to add a index changed event handler. In the event handler, write the VB.net equivalent of this:

protected void ddlPageSelector_SelectedIndexChanged(object sender, EventArgs e) {

GridView1.PageIndex = ((DropDownList)sender).SelectedIndex;

GridView1.DataBind();

}

Related : Clickable GridView Headers .

Clickable GridView Headers

rajbk — Fri, 04 Aug 2006 16:40:00 GMT

By default, you can sort on the columns of a GridView by clicking on the LinkButton in the header of a column that has a SortExpression defined. This post is going to attempt three things.

Sort the column by clicking anywhere in the header cell
Add a sort indicator to cells that are sortable. Cells that are sortable will have a "neutral" icon. Note in the screen capture below that UnitsInStock does not have a "neutral" icon because it does not have a SortExpression defined.
Highlight the column of data that is being sorted.

The idea is to add an onclick attribute that calls a javascript function to all GridView header cells that are sortable.

In the javscript function, we determine which element raised the event. If the element that raised the event is not the LinkButton, we find the LinkButton and invoke its onclick or href attribute method based on the GridView EnableSortingAndPagingCallbacks property. When the EnableSortingAndPagingCallbacks is set to true, we invoke the onclick method otherwise we invoke the method the href attribute points to.

We are checking which element raised the event in the javscript function to prevent the postback or callback from being called twice. This is because, without this check, clicking on the LinkButton will fire the method as well as bubble the event up to its parent cell causing it to be fired again (since we have added an onclick attribute to the cell). The javascript function calls the postback or callback method only if the element that raised the event is not the LinkButton.

    public void MakeGridViewHeaderClickable(GridView gridView, GridViewRow gridViewRow) {
        if (gridViewRow.RowType == DataControlRowType.Header) {
            for (int i = 0; i < gridView.Columns.Count; i++) {
                string sortExpression = gridView.Columns[i].SortExpression;
                TableCell tableCell = gridViewRow.Cells[i];
 
                //Make sure the column we are working with has a sort expression
                if (!string.IsNullOrEmpty(sortExp ression)) {
                    //Enumerate the controls within the current cell and find the link button.
                    foreach (Control gridViewRowCellControl in gridViewRow.Cells[i].Controls) {
 
                        LinkButton linkButton = gridViewRowCellControl as LinkButton;
 
                        if ((linkButton != null) && (linkButton.CommandName == "Sort")) {
 
                            //Add an onclick attribute to the current cell
                            tableCell.Attributes.Add("onclick", "RequestData('" + linkButton.ClientID + "', this, event)");
 
                            tableCell.Style.Add(HtmlTextWriterStyle.Cursor, "hand");
                            tableCell.Style.Add(HtmlTextWriterStyle.Cursor, "pointer");
                            break;
                        }
                    }
                }
            }
        }
    }
 
    protected void GridView1_RowDataBound(object sender, GridViewRowEventArgs e) {
        MakeGridViewHeaderClickable(GridView1, e.Row);
    } 

The javascript function is shown below

    <script language="javascript" type="text/javascript">
    function RequestData(linkId, cellElement, evt) {
        var evtSource;
 
        evt = (evt)? evt : window.event;
        evtSource = (evt.srcElement)? evt.srcElement : evt.target;
 
        //When a hyperlink is clicked, Safari returns the text node as the source element rather
        //than the hyperlink. parentNode will give us the hyperlink element.
        //ref: http://developer.apple.com/internet/webcontent/eventmodels.html
        if (evt.target) {
            if (evt.target.nodeType == 3) {
                evtSource = evtSource.parentNode;
            }
        }
 
        //If event was raised from an element other than the LinkButton
        if ((evtSource.getAttribute("id") != linkId) && (evt.type == "click")) {
 
            //Get a collection of "a" tags inside the cell        
            var linkCollection = cellElement.getElementsByTagName("a");
            for (var i = 0; i < linkCollection.length; i++) {
 
               //If the link button has an onclick attribute, call the onclick.
               //The onclick attribute is present when the GridView is using callback
               //example: onclick="java script:__gvGridSort1_GridView1.callback(...); return false;"
               var onClickAttribute = linkCollection[i].getAttribute("onclick");
               if (onClickAttribute != null) {
                linkCollection[i].onclick();
                break;
               }
 
               //If the link button has a href attribute, set the location of the page
               //to the href value.
               //The href attribute is used when the GridView is not using callbacks
               //example: href="java script:__doPostBack('GridSort1$GridView1','Sort$UnitsOnOrder')" 
               var hrefAttribute = linkCollection[i].getAttribute("href");
               this.location.href = hrefAttribute;
               break;
            }
        }
    }
 
    </script>

If you run the above code, you will notice that it is different from screen capture above because the sort image and column highlighting are missing. To implement this, we need to add some code to the MakeGridViewHeaderClickable method as shown below.

    public void MakeGridViewHeaderClickable(GridView gridView, GridViewRow gridViewRow) {
 
        if (gridViewRow.RowType == DataControlRowType.Header) {
 
            for (int i = 0; i < gridView.Columns.Count; i++) {
 
                string sortExpression = gridView.Columns[i].SortExpression;
                TableCell tableCell = gridViewRow.Cells[i];
 
                //Make sure the column we are working with has a sort expression
                if (!string.IsNullOrEmpty(sortExp ression)) {
 
                    System.Web.UI.WebControls.Image sortDirectionImageControl;
 
                    //Create an instance of a Image WebControl
                    sortDirectionImageControl = new System.Web.UI.WebControls.Image();
 
                    //Determine the image url based on the SortDirection
                    string imageUrl = "~/Images/sort_neutral.gif";
                    if (sortExpression == gridView.SortExpression) {
                        imageUrl = (gridView.SortDirection == SortDirection.Ascending) ?
                            "~/Images/sort_asc.gif" : "~/Images/sort_desc.gif";
                    }
 
                    //Add the Image Web Control to the cell
                    sortDirectionImageControl.ImageUrl = imageUrl;
                    sortDirectionImageControl.Style.Add(HtmlTextWriterStyle.MarginLeft, "10px");
                    tableCell.Wrap = false;
                    tableCell.Controls.Add(sortDirectionImageControl);
 
                    //Enumerate the controls within the current cell and find the link button.
                    foreach (Control gridViewRowCellControl in gridViewRow.Cells[i].Controls) {
 
                        LinkButton linkButton = gridViewRowCellControl as LinkButton;
 
                        if ((linkButton != null) && (linkButton.CommandName == "Sort")) {
 
                            //Add an onclick attribute to the current cell
                            tableCell.Attributes.Add("onclick", "RequestData('" + linkButton.ClientID + "', this, event)");
 
                            tableCell.Style.Add(HtmlTextWriterStyle.Cursor, "hand");
                            tableCell.Style.Add(HtmlTextWriterStyle.Cursor, "pointer");
                            break;
                        }
                    }
                }
            }
        }
 
        //Enuerate all the rows and change the color of the column that is being sorted
        if (gridViewRow.RowType == DataControlRowType.DataRow) {
 
            for (int i = 0; i < gridViewRow.Cells.Count; i++) {
                if ((!String.IsNullOrEmpty(gridView.SortExpr ession)) &&
                   (gridView.Columns[i].SortExp ression == gridView.SortExp ression)) {
                    Color sortColumnBgColor;
 
                    sortColumnBgColor = (gridViewRow.RowState != DataControlRowState.Alternate) ?
                        ColorTranslator.FromHtml("#d7e3f1") : ColorTranslator.FromHtml("#f7fbff");
 
                    gridViewRow.Cells[i].BackColor = sortColumnBgColor;
                }
            }
        }
    }

You can also use this with HeaderTemplates. Just make sure your HeaderTemplate contains a LinkButton with a CommandName attribute set to "Sort" as shown below:

<asp:TemplateField HeaderText="ProductID" SortExpression="ProductID">
    <ItemTemplate>
        <asp:Label ID="Label1" runat="server" Text='<%# Bind("ProductID") %>'></asp:Label>
    </ItemTemplate>
    <HeaderTemplate>
        <asp:LinkButton runat="server" CommandName="Sort" CommandArgument="ProductID"
            Text="ProductID"></asp:LinkButton>
    </HeaderTemplate>
</asp:TemplateField>

You can easily make these transparent sort icons by working at the pixel level ( I used Photoshop)

The MakeGridViewHeaderClickable method can be placed in a Utility class if you so desire. A reference to the GridView can be obtained by using gridViewRow.Parent.Parent or (GridView) gridViewRow.NamingContainer if you don't want to pass in a GridView reference to the method.

Tested on IE 6.0.2900, Firefox 1.5.0.6 and Safari 1.3.2

Note: I had to add a space in some variables because Community Server (running this blog) was blocking my scripts. Example: sortExp ression.

Virtual Sever and Port Security

rajbk — Mon, 15 May 2006 22:01:00 GMT

If you are running Virtual Server and your Virtual Machine is having trouble obtaining an IP Address from your DHCP server, it could be because you have port security turned on on your switch.

AFAIK, when Virtual sever is directly connected to the host network or if it is configured to perform NAT, it configures the physical network adapter to run in Promiscuous mode. More importantly, as described here, outbound packets from the Virtual machine will contain the MAC address of the Virtual machine.

So, you now have a NIC advertising two MAC addresses (the host os and the VM). When you have port security turned on, the switch will ignore packets from the second MAC address.

To fix this, go to your switch and either turn off port security for the port used by your physical network adapter or increase the max number of mac addesses to secure on the port.

I did not find any info about this on Google which lead me to post this. If any one has more information, please post here.

Health monitoring in asp.net 2.0 - logging events

rajbk — Fri, 10 Feb 2006 00:18:00 GMT

I was about to use the Logging Application Block of the Enterprise Library 2.0 when I found out about the built in Health Monitoring feature in ASP.net 2.0. IMHO, the Logging block is great for an enterprise app but might be overkill for smaller apps.

With just a few lines in web.config, you can easily add health monitoring to your application as described here.

You get the following providers out of the box:

SimpleMailWebEventProvider

TemplatedMailWebEventProvider

SqlWebEventProvider

EventLogWebEventProvider

TraceWebEventProvider

WmiWebEventProvider

MSDN even has an example of how to create a custom provider that writes specified health monitoring event information to a local file.

Very cool J