DropDownList Control in ASP.Net

In previous asp.net server control post we had discussed about MultiView Control and ListBox Control and FileUpload Control and CheckBox Control and RadioButton Control and Adrotator Control and TextBox Control.

ASP.Net DropDownlList Control

The DropDownList control is asp.net web server control. we can use dropdownlist control for hold group of items.

The dropdownlist control is used to store the multiple items and allow user to select only one item from it.

The dropdownlist control is also known as combo box control. In dropdownlist control we can store multiple items but we can select only one item at a time, that’s why it is also known as Single Row Selection Box.

In asp.net there are main two control to store multiple items with it, the dropdownlist and the listbox control.

Learn about listbox control to click here…

There is only SelectionMode difference between dropdownlist control and listbox control. The dropdownlist has no SelectionMode, so we can not selection multiple item in dropdownlist.

DropDownList Control Example in ASP.Net C#

Here, we understand the dropdownlist control with an asp.net example.

Create a new web application in asp.net with a web forms. below screen shows how to take dropdownlist control on web page from toolbox.

Now, for add new items in dropdownlist go to the Items property shows like below asp.net figure.

In dropdownlist control all the elements are known as items of dropdownlist, and each items consist with text and value attributes.

If we add items in to dropdwonlist control we must provide Text and Value for each items.

Text = Text Property specify the Text display in the dropdownlist.

Value = The value property is invisible value, but we can get the value while programming.

Here is the html code of dropdownlist control with five items.

<asp:DropDownList ID="DropDownList1" runat="server" Height="16px" Width="132px">
  <asp:ListItem Value="01">MEERA</asp:ListItem>
  <asp:ListItem Value="02">RAM</asp:ListItem>
  <asp:ListItem Value="03">JAY</asp:ListItem>
  <asp:ListItem Value="04">RAHUL</asp:ListItem>
  <asp:ListItem Value="05">MANOJ</asp:ListItem>
  <asp:ListItem Value="06">REENA</asp:ListItem>
</asp:DropDownList>

There are other some important properties of dropdownlist:

DropDownList1.SelectedIndex = Returns the Index of selected item of dropdownlist. (Index always start from Zero).

DropDownList1.Items.Count

Below example show the total number of item count in dropdownlist control.

 protected void btncount_Click(object sender, EventArgs e)
 {
    Label1.Text = "The Count = "+DropDownList1.Items.Count.ToString();
 }

DropDownlList1.SelectedItem.Text

Example : How to get selected item from dropdownlist control in asp.net.

protected void btnselectedtext_Click(object sender, EventArgs e)
 {
    Label1.Text = "Text = "+DropDownList1.SelectedItem.Text;
 }

DropDownList1.SelectedValue

Example : How to get Selected Value from dropdownlist control in asp.net.

protected void btnselectedvalue_Click(object sender, EventArgs e)
 {
    Label1.Text = "Value = " +DropDownList1.SelectedValue;
 }

DropDownList1.SelectedIndex

Example: Get Selected Index in dropdownlist control in asp.net.

 protected void btnselectedIndex_Click(object sender, EventArgs e)
  {
    Label1.Text = "Index = " +DropDownList1.SelectedIndex.ToString();
  }

DropDownList1.Items.Clear()

Example : Clear all items in dropdownlist control.

 protected void btnclear_Click(object sender, EventArgs e)
  {
     DropDownList1.Items.Clear();
     Label1.Text = "ListBox Cleared";
  }

DropDownList1.Items.Add(“text”);

Example : Add new item in dropdownlist control.

protected void btnadd_Click(object sender, EventArgs e)
 {
     DropDownList1.Items.Add("Meera");
     Label1.Text = "Item Added";
 }

DropDownList1.Items.Remove(“text”)

Example : Remove items from dropdownlist control.

protected void btnremove_Click(object sender, EventArgs e)
 {
     DropDownList1.Items.Remove("Meera");
     Label1.Text = "Item Removed";
 }

DropDownList1.Items.Insert(int index, “text”);

Example : Add new item at specific location in dropdownlist control. The index is the indicate the location of newly added item in dropdownlist control.

protected void btnadd_Click(object sender, EventArgs e)
 {
     DropDownList1.Items.Insert(2,"Meera");
     Label1.Text = "Item Inserted";
 }

 

DropDownList1.Items.RemoveAt(int index)

Example : Remove items from dropdownlist control at specify the index location. The index start from zero.

protected void btnremove_Click(object sender, EventArgs e)
 {
     DropDownList1.Items.RemoveAt(2);
     Label1.Text = "Item Removed";
 }

The C# code behind code for all buttons click events.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;

public partial class Default6 : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {

    }
    protected void btncount_Click(object sender, EventArgs e)
    {
        Label1.Text = "The Count = " + DropDownList1.Items.Count.ToString();
    }
    protected void btnselectedtext_Click(object sender, EventArgs e)
    {
        Label1.Text = "Text = " + DropDownList1.SelectedItem.Text;
    }
    protected void btnselectedvalue_Click(object sender, EventArgs e)
    {
        Label1.Text = "Value = " + DropDownList1.SelectedValue;
    }
    protected void btnselectedIndex_Click(object sender, EventArgs e)
    {
        Label1.Text = "Selected Index = " + DropDownList1.SelectedIndex.ToString();
    }
    protected void btnclear_Click(object sender, EventArgs e)
    {
        DropDownList1.Items.Clear();
        Label1.Text = "ListBox Cleared";
    }
    protected void btnadd_Click(object sender, EventArgs e)
    {
        DropDownList1.Items.Add("Meera");
        Label1.Text = "Item Added";
    }
    protected void btnremove_Click(object sender, EventArgs e)
    {
        DropDownList1.Items.Remove("Meera");       
        Label1.Text = "Item Removed";
    }
}