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Creating a Read Only DropDownList

, 4 Jun 2008
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This explains how to extend a DropDownList to give it a ReadOnly attribute.

Introduction

When a control is disabled, it can not be styled in IE, and the default style sucks. So, I searched for a long time trying to figure out the best way of creating a dropdownlist control that has a ReadOnly property, which would be much more readable to a user, while still maintaining all the benefits of a DropDownList control. After much searching, I decided to try the easy road, and came up with this control.

A TextBox set as Enabled, Disabled, or ReadOnly will look three different ways. This allows a DropDownList to have that same behavior.

Using the code

Basically, I decided to create my own control derived from DropDownList. I had it internally contain a TextBox, and when it went to be rendered, it just rendered the selected item, or the dropdown list, depending on if the ReadOnly property was set.

using System.Web.UI.WebControls

public class DropDownListReadOnly : DropDownList
{
    private bool _readOnly;
    private TextBox tb = new TextBox();
    public bool ReadOnly
    {
        get
        {
            return _readOnly;
        }
        set
        {
            _readOnly = value;
        }
    }

    protected override void Render(System.Web.UI.HtmlTextWriter writer)
    {
        if (_readOnly)
        {
            tb.Text = this.Text;
            tb.ReadOnly = true;
            tb.RenderControl(writer);
        }
        else
            base.Render(writer);
    }
}

Setup

The easiest way of using this project is to create your own Web Control Library, and then add this class to your library. You can then insert the control into the VS2005 Designer by the normal method (right click on the Toolbox, pick the Add tab; then, right click the tab and pick Choose Items, and browse to the compiled DLL).

History

To-Do: Might need some error checking in the Render method.

License

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

About the Author

DSpazman
Web Developer
United States United States
No Biography provided

Comments and Discussions

 
GeneralPostback problem Pinmembersykiemikey4-May-09 5:31 
GeneralAlternate option PinmemberRenish@IT26-Feb-09 23:02 
GeneralGood idea Pinmemberdave.dolan17-Dec-08 5:42 
GeneralInteresting approach. PinmemberRajib Ahmed5-Jun-08 17:01 
QuestionHuh? PinmemberPIEBALDconsult4-Jun-08 8:10 
AnswerRe: Huh? PinmemberDSpazman4-Jun-08 8:44 
PIEBALDconsult wrote:
private TextBox tb = new TextBox();
 
Why not a string?
 
private string tb = "";

 
Because:
1) A TextBox looks more like a Dropdownlist.
2) Assuming your website has CSS styles for TextBoxes already, it'll pick up those styles and not need to be personally styled by you.
 
If you wished, you could change it to a string, create whatever formatting you wanted for it, if you want to box it in, display a picture, whatever. I was just doing this for an example.
 

PIEBALDconsult wrote:
And at any rate, the intent of your article is unclear.
What are you trying to accomplish?

 
3) The intent is to create a DropDownList with a ReadOnly attribute. If you look at a textbox, and make one normal, one ReadOnly, and one Disabled, you have 3 different looks. The ReadOnly has a background color, and can not be changed, but you can select the text inside. the Disabled has an aweful font and background color that makes it very hard to read, and you cannot select the Text inside it.
 
DropDownLists only have an Enabled and Disabled mode, not a ReadOnly. This control extends the DropDownList to include a ReadOnly Version.
GeneralRe: Huh? Pinmember leppie 4-Jun-08 9:22 
GeneralRe: Huh? PinmemberSteven Berkovitz4-Jun-08 10:59 
GeneralRe: Huh? PinmemberPIEBALDconsult4-Jun-08 12:07 
GeneralRe: Huh? PinmemberDSpazman4-Jun-08 12:46 
GeneralRe: Huh? PinmemberPIEBALDconsult4-Jun-08 13:41 
GeneralRe: Huh? PinmemberMohammed Gouda17-Jun-08 1:47 

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