Auto Resize Dropdown Box

Auto Resize Dropdown

Sometimes, using a built-in dropdown control does not meet your requirement. Suppose a dropdown box contains text that is longer in length than your box; therefore, the width of the dropdown will increase as the text length increases. But, an increase in the dropdown's size affects your form design. You don't have enough space on your page to fit this lengthy dropdown box. In that case, you can use this Auto Resize Dropdown box.

Create a blank solution; in the solution, add a class library; and in the class file, add the following code. This code shows that, at the time of rendering the control, with the help of a style you can maintain the initial width of your dropdown box.

Note: You must inherit WebControls.DropDownList.
Inherits WebControls.DropDownList
   Protected Overrides Sub Render(ByVal writer As _
      System.Web.UI.HtmlTextWriter)
      writer.Write("<div style='width:" & Me.Width.ToString & "'>")
      MyBase.Render(writer)
      writer.WriteEndTag("div")
End Sub

At the time of initialization, it will call JavaScript functions. These JavaScript functions will attach with onactivate and ondeactivate events.

Private Sub AutoSizeDropDown_Init(ByVal sender As Object, _
   ByVal e As System.EventArgs) Handles Me.Init
   Dim ControlsJS As String
   ControlsJS = "<script type=""text/javascript"" src=""" & 
   HttpRuntime.AppDomainAppVirtualPath & "/js/CustomControls.js""> _
   </script>"
   Me.Attributes.Add("originalWidth", "")
   Me.Attributes.Add("onactivate", "RearrangeDdnWidth(this)")
   Me.Attributes.Add("ondeactivate", "ResetDdnWidth(this)")
   Page.ClientScript.RegisterClientScriptBlock(Me.GetType(), _
      "ControlsJS", ControlsJS)
End Sub

After building the solution, add a new web site in your solution. In the default.aspx page, register your DLL with the page.

<%@ Register Assembly="AutoDropDown"
    Namespace="AutoDropDown" TagPrefix="cc1" %>

After that, you can add the dropdown:

<cc1:AutoSizeDropDown runat="server"
                      ID="AutoSizeDropDown1"
                      Width="50px"></cc1:AutoSizeDropDown>

The complete source code is available with this article.



About the Author

Ashish Singh

I am working as I.T. Analyst at Tata Consultancy Services Ltd. I have 4+ years of experience in Microsoft Technologies. I have worked primarily as a Dot Net Developer with C# and VB.Net as code behind.

Downloads

Comments

  • There are no comments yet. Be the first to comment!

Leave a Comment
  • Your email address will not be published. All fields are required.

Top White Papers and Webcasts

  • Complex hybrid environments can make it difficult to track interdependencies, increasing the risk of disrupting critical business services. In this white paper by EMA, you'll learn how application discovery and dependency mapping can help you: Meet granular targets for availability, cost, and time-to-revenue for cloud services. Accelerate mean time to repair (MTTR) while communicating better with stakeholders. Manage even the most complex hybrid environments more efficiently and effectively Understand the …

  • When individual departments procure cloud service for their own use, they usually don't consider the hazardous organization-wide implications. Read this paper to learn best practices for setting up an internal, IT-based cloud brokerage function that service the entire organization. Find out how this approach enables you to retain top-down visibility and control of network security and manage the impact of cloud traffic on your WAN.

Most Popular Programming Stories

More for Developers

RSS Feeds

Thanks for your registration, follow us on our social networks to keep up-to-date