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Posted 19 Mar 2007

Multi select Dropdown list in ASP.NET

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Multiselect dropdown list control allows the user to select multiple items from the list and displays the selected items in comma separated format.


The Dropdown list in ASP.NET is used to select a single item from the list. The Listbox control is used to select multiple items, but it takes up more space on the page. An ASP.NET page which contain many of these controls may make it difficult to find the proper space and alignment for each control.

To overcome this, I am introducing a Multi Select Dropdown list box control. It is a user control and can be used directly on pages very easily. It allows the user to select multiple items from the list and the selected items will be displayed in comma separated format in the text area, and it can also persist the selected items.

How to use this Control

The user control MultiSelectDropDown can be placed on any Web page.

Drag and drop the MultiSelectDropDown control on the web page where you want to use the multi select feature.

Populate the dropdown with appropriate values. In my sample it has been populated as follows:

private void Page_Load(object sender, System.EventArgs e)
   if (!Page.IsPostBack )
    MultiSelectDropDown1.List.Items.Add(new System.Web.UI.WebControls.ListItem("Apple","1")) ;
    MultiSelectDropDown1.List.Items.Add(new System.Web.UI.WebControls.ListItem("Grapes","2")) ;
    MultiSelectDropDown1.List.Items.Add(new System.Web.UI.WebControls.ListItem("Orange","3")) ;
    MultiSelectDropDown1.List.Items.Add(new System.Web.UI.WebControls.ListItem("Strawberry","4")) ;
    MultiSelectDropDown1.List.Items.Add(new System.Web.UI.WebControls.ListItem("Water Melon","5")) ;

System.Collections.ArrayList selTexts = MultiSelectDropDown1.SelectedTexts;

SelectedTexts property returns an Arraylist of the selected items in the list, SelectedValues property

The following are the main public properties provided by this control:

SelectedTexts Arraylist of selected texts in the list
SelectedValues Arraylist of values corresponding to the selected items in the list
SelectedText Comma separated string of selected texts
SelectedItems Arraylist of values and texts corresponding to the selected items in the list
ListWidth Set/Get the width of the control
List List of items


The following screenshot shows how to select multiple items from the list:

The width of the control can be changed by the ListWidth property of the control.

MultiSelectDropDown1.ListWidth = Convert.ToDouble(txtWidth.Text);

The following image shows that the control width has changed to 150 from 250 when you enter 150 in the Dropdown width field and click on Set DD width button.

The dropdown also shows the tooltip of the selected texts in comma separated format. It helps the user to find out what the selected items are, without clicking on the dropdown if the width of the dropdown is not large enough to display all the selected texts.

The following image shows the tooltip of the text:

The selected items in the list will be added to the Selected Fruits Listbox when you click on Display selected fruits button.

The code is given below:

System.Collections.ArrayList selItems = MultiSelectDropDown1.SelectedTexts;
ListBox1.DataSource = selItems;

The following code shows how to set the selected items of the control:

ArrayList selectedItems = new ArrayList();
// Select the items from the list
foreach (System.Web.UI.WebControls.ListItem selItem in ListBox1.Items )
   System.Web.UI.WebControls.ListItem li = ListBox1.Items.FindByText(selItem.Text ) ;
MultiSelectDropDown1.SelectedItems =selectedItems;

It sets the SelectedItems property of the control with the ArrayList of items.


This is a very useful and simple control and can be used on any web page irrespective of the .NET version.


This article has no explicit license attached to it but may contain usage terms in the article text or the download files themselves. If in doubt please contact the author via the discussion board below.

A list of licenses authors might use can be found here


About the Author

Deepthi Viswanathan Nair
United States United States
No Biography provided

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Comments and Discussions

GeneralMulti-Select with Master page Pin
Member 33793814-Mar-09 11:22
memberMember 33793814-Mar-09 11:22 
GeneralRe: Multi-Select with Master page Pin
Donna Belville28-Apr-09 9:44
memberDonna Belville28-Apr-09 9:44 

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Web02 | 2.8.180111.1 | Last Updated 19 Mar 2007
Article Copyright 2007 by Deepthi Viswanathan Nair
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