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

  • Organizations are increasingly gravitating toward mobile-first application development as they assess the need to revamp their application portfolios to support touch computing and mobility. Consumerization has brought higher expectations for application usability along with the mobile devices themselves. Enterprises are increasingly shifting their new application acquisitions and development efforts toward mobile platforms. With this backdrop, it is natural to expect application platform vendors to invest in …

  • Cloud computing isn't new, but it's still a hot topic in technology circles. Moving to the cloud has done great things for many businesses. When it comes to handling a basic business necessity, cloud computing has brought many improvements to overall business continuity. Using the cloud for DR makes a lot of sense for many, but it's not exactly the most simple concept. Read this eBook to find answers to all the key questions IT professionals have about cloud-based disaster recovery, and helpful info around the …

Most Popular Programming Stories

More for Developers

RSS Feeds

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