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How to develop a Simple Vertical Text Scroller custom server control in ASP.NET


Introduction

Couple years ago, I was looking for a simple text scroller application to replace our text scoller that was based on Java and I found the application Cross Browser marquee II on dynamicdrive.com. I have modified it to tailor my requirement. The main modification I made to the scroller was the addition of two buttons that controlled the flow of the vertical scroll content. Recently, I did a quick search on Google and found out that handful (50+) of websites were still using this application. Below are the few of them.

Check it out.

http://cherryle.win.aplus.net/index.asp
http://www.hydroqual.com
http://www.sabugacenter.com
http://www.ehub.si
http://www.globalnews-indonesia.com
http://www.mmtv.co.za/index.htm
http://www.opcfoundation.org

Moving forward, I have converted this application to ASP.NET custom server control. Now, the ASP.NET developers can drag and drop the control to the page without copy and paste between the web applications. Below is a step by step tutorial on how I have accomplished this. Hope this tutorial will give someone an idea on how to create a custom server control.

Download the original application/ script

cmarquee2.htm

Note

I have broken the cmarquee2.htm page into three different sections, namely Style Sheet, JavaScript and static HTML elements/ tags.

Create Class Library

  1. Open VS 2005/2008. Go to File, New, Project, Visual C# and select Class Library template and fill up the required field.
    New Project
     
  2. Rename the class1.cs to TextScroller.cs

Adding Style Sheet

Right click the project, Add, New Item, Visual C# Project Items, Select Style Sheet from the available templates. I named it TextScroller.css. Extract all the Style Sheet from cmarquee2.htm into TextScroller.css

Adding JavaScript

Right click the project, Add, New Item, Visual C# Project Items, Select Jscript from the available templates. I named it TextScroller.js. Extract all the JavaScript from cmarquee2.htm into TextScroller.js

Add New Item

Adding New Folder

Right click the MyTextScroller project, Add, New Folder, rename the folder to images. Place all the images in this folder.

Adding System.Web References

Right click on the MyTextScroller project, Add Reference. In the .NET tab locate the System.Web component name, select it and click Ok.

Adding Web.System Reference

Check Point

The structure of the project should look like the picture from below if you follow all the above step correctly.

Project Structure

Embedding the Resources

Right click one of the images, select Properties, and change the Build Action value from Content to Embedded Resource. Repeat the same step for all the other images.
 
Embed Images 

Repeat the above step for the JavaScript and Style Sheet.

Double click the AssemblyInfo.cs. Add the following to the bottom of the file.

[assembly: System.Web.UI.WebResource("MyTextScroller.TextScroller.css", "text/css")]
[assembly: System.Web.UI.WebResource("MyTextScroller.TextScroller.js", "text/javascript", PerformSubstitution = true)]
[assembly: System.Web.UI.WebResource("MyTextScroller.images.nav-arrow-down-hover.gif", "image/gif")]
[assembly: System.Web.UI.WebResource("MyTextScroller.images.nav-arrow-down.gif", "image/gif")]
[assembly: System.Web.UI.WebResource("MyTextScroller.images.nav-arrow-up-hover.gif", "image/gif")]
[assembly: System.Web.UI.WebResource("MyTextScroller.images.nav-arrow-up.gif", "image/gif")]

Note

Default Namespace

The syntax - [assembly: System.Web.UI.WebResource("Default Namespace.File Location.File Name", "Type")]

Example 1

My Default Name Space is MyTextScroller
My JavaScript File name is TextScroller.js
And I'll end up having this line in my AssemblyInfo.cs
[assembly: System.Web.UI.WebResource("MyTextScroller.TextScroller.js", "text/javascript")]>

Example 2

My Default Name Space is MyTextScroller
All my images are in images folder
My image name is nav-arrow-down-hover.gif
And I'll end up having this line in my AssemblyInfo.cs 
[assembly: System.Web.UI.WebResource("MyTextScroller.images.nav-arrow-down.gif", "image/gif")]

TextScroller.cs

The TextScroller.cs will hold all the static HTML elements in the cmarquee2.htm. Please look at the code, is pretty straight forward. Here is a brief explanation.

Add design-time attributes to provide custom metadata that will be used to display the control in the visual designer at design time

namespace MyTextScroller
{
    [
        AspNetHostingPermission(SecurityAction.Demand, Level = AspNetHostingPermissionLevel.Minimal),
        AspNetHostingPermission(SecurityAction.InheritanceDemand, Level = AspNetHostingPermissionLevel.Minimal),
        ParseChildren(true, "innerHTML"),
        DefaultProperty("innerHTML"),
        ToolboxData("<{0}:TextScroller runat=\"server\"> </{0}:TextScroller>")
    ]
    public class TextScroller : WebControl, INamingContainer
    {

Additional Reading/ Information


The ToolboxData attribute specifies the default tag generated for the TextScroller control when it is dragged from the Toolbox into a page at design time.

ParseChildren
AspNetHostingPermission

//Properties to adjust the width and height of the div and set the innerHTML od the div

Working with Web Resources in ASP.NET 2.0

#region Public Properties

//width of the div
private Unit width = Unit.Pixel(260);
public override Unit Width
{
    get { return width; }
    set { EnsureChildControls(); width = value; }
}

//height of the div
private Unit height = Unit.Pixel(160);
public override Unit Height
{
    get { return height; }
    set { EnsureChildControls(); height = value; }
} 

//content
private string _innerHTML = "Your Content here";
[  
    Browsable(true), //display this property in designer
    Category("Appearance"),
    DefaultValue("Your Content Here"),
    Description("The Content to Display."),
    PersistenceMode(PersistenceMode.InnerDefaultProperty)
]

public virtual string innerHTML
{
    get
    {
        return _innerHTML;
    }
    set
    {
        EnsureChildControls();
        _innerHTML = value;
    }
}
#endregion

Example - Images

Image myImage = new Image();
ClientScriptManager cs = Page.ClientScript;
Type rsType = this.GetType();
myImage.ImageUrl = cs.GetWebResourceUrl(rsType, "MyTextScroller.images.nav-arrow-up.gif");

Example - JavaScript

Type rsType = this.GetType();
this.Page.ClientScript.RegisterClientScriptInclude(
rsType, "TextScroller_Script_Name",
Page.ClientScript.GetWebResourceUrl(rsType, " MyTextScroller.TextScroller.js"));

Example - Style Sheets

Type rsType = this.GetType();
string csslink = "<link rel='stylesheet' type='text/css' href='" +
Page.ClientScript.GetWebResourceUrl(rsType, "MyTextScroller.TextScroller.css") + "' />";
LiteralControl include = new LiteralControl(csslink);
this.Page.Header.Controls.Add(include);

//using the embeded JavaScript and Style Sheet

protected override void OnInit(EventArgs e)
{
    base.OnInit(e);
    //access embedded Resource
    this.Page.ClientScript.RegisterClientScriptInclude(
                this.GetType(), "TextScroller",
                Page.ClientScript.GetWebResourceUrl(this.GetType(),
                "MyTextScroller.TextScroller.js"));

    // create the style sheet control and put it in the document header
    string csslink = @"<link rel='stylesheet' type='text/css' href='" + Page.ClientScript.GetWebResourceUrl(this.GetType(), "MyTextScroller.TextScroller.css") + "' />";
    LiteralControl include = new LiteralControl(csslink);
    this.Page.Header.Controls.Add(include);

}

//write the output to the page that are in the cmarquee2.htm page

protected override void OnPreRender(EventArgs e)
{
    base.OnPreRender(e);
} 

protected override void Render(HtmlTextWriter output)
{
    EnsureChildControls();
    output.Write(GenerateDiv());
} 

private string GenerateDiv()
{
    StringBuilder b = new StringBuilder();
    ClientScriptManager cs = Page.ClientScript;
    Type rsType = this.GetType();
    b.Append("<div style=\"width:");
    b.Append(width.Value);
          see attached code ........
          ........
    return b.ToString();
} 

protected override void CreateChildControls()
{
    Controls.Clear();
}

protected override void OnLoad(EventArgs e)
{
    base.OnLoad(e);
} 

Individualizing the Control: Add a custom toolbox icon for the control

  1. Create an icon from any of the links below. This is free.

    dynamicdrive
    genfavicon
  2. What is the name of your class? For instance my class name is TextScroller

    public class TextScroller : WebControl, INamingContainer

    Then I named the icon TextScroller.ico. Place it in the project root directory and change the Build Action to Embeded Resource

Embed Icon

Adding the Control to the Toolbox
  1. Go to View, Toolbox, Right click any place in the Toolbox, Add Tab, I name it MyTextScroller.
  2. Right click MyTextScroller, Choose Items, .NET Framework Components Tab, Browse, find the MyTextScroller.dll, click Ok.
  3. You should see something like this on the Toolbox.
Toolbox Icon

How to test it? / Using the code

Add Refenence
  1. Right click on the solution, Add, New Web Site, ASP.NET Web Site/ ASP.NET AJAX-Enabled Web Site

    Add New Website
  2. Right click the TestMyTextScroller, Add References, Project Tab, MyTextScroller project, Ok.

    Add Reference
Drag the TextScroller from the Toolbox to the Default.aspx. Try one of the following

<cc1:TextScroller ID="TextScroller1" runat="server"> 
  My test content here. 
  My Blog 
  More text here….
      </cc1:TextScroller>

Or

protected void Page_Load(object sender, EventArgs e)
{
    TextScrollerContent();
} 

internal void TextScrollerContent()
{
   StringBuilder sbContent = new StringBuilder(string.Empty);  

   sbContent.Append("My test content here. <br />");
   sbContent.Append("<a href=\"http://blog.ysatech.com\">My Blog</a> <br />");
   sbContent.Append("More text here…");   

   TextScroller1.innerHTML = sbContent.ToString();
}

You should see something like below:

Results

Points of Interest

Do not use any custom server control from any unknown sources that have JavaScript embedded to it. Go through all the JavaScript and make sure that no potential malicious scripts embedded in it.

Next improvement:
  1. Support multiple instances, currently this version work only with one instance of the TextScroller on the same page
  2. Allow user to change the image button during design time

Conclusion

Here are the lists of items we have covered in this article:
  1. How to create a Custom Server Control
  2. How to embed resources
  3. How to access embedded Resource
  4. How to include custom toolbox icon
  5. How to test the new control

References

http://aspalliance.com/726
http://www.dynamicdrive.com/dynamicindex2/cmarquee2.htm%2520
http://www.codeproject.com/
http://msdn.microsoft.com/en-us/library/system.web.ui.control.ensurechildcontrols.aspx
http://msdn.microsoft.com/en-us/library/system.web.aspnethostingpermission.aspx
http://ondotnet.com/pub/a/dotnet/excerpt/progaspdotnet_14/index2.html
http://msdn.microsoft.com/en-us/library/system.web.ui.parsechildrenattribute.aspx


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