How To Get Options Into the DropDownList Control 

1. If you are using Visual Studio, drag the DropDownList control from the toolbox onto the web form. Make sure you choose the control from the WebForms tab and not the HTML tab. After positioning the control where you want, resizing it and so on, you can manually enter the items into the list using Visual Studio. Go to the properties dialog for the control. If the properties dialog is not visible, right click on the control and select PROPERTIES from the menu. Find the entry for "Items" and click on the ellipsis button to bring up the ListItem Collection Editor. Click the ADD button on the left side of the editor. On the right side, enter "Georgia" in the text field and "GA" in the value field. Now click ADD again and enter "Florida" in the text field and "FL" in the value field. Click ADD again and enter "Alabama" in the text field and "AL" in the value field. Click the OK button. Now you have a DropDownList control with three list items. The text portion of each item will display the state name. The corresponding value will be the abbreviation of the selected state. 

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2. You can access the text and value properties of the selected item in code as follows: 

Dim strVariable as String
strVariable = DropDownList1.SelectedItem.Text - To access the text portion
strVariable = DropDownList1.SelectedItem.Value - To access the value portion

3. If you are not using Visual Studio or if you just allergic to drag 'n drop, you can code the above directly following the following syntax:

<asp:DropDownList id="DropDownList1" runat="server">
<asp:ListItem Value="GA">Georgia</asp:ListItem>
<asp:ListItem Value="FL">Florida</asp:ListItem>
<asp:ListItem Value="AL">Alabama</asp:ListItem>
</asp:DropDownList>

4. You can write code to add your items also. Here is an example of how you might populate the control when the page loads for the first time. Notice, however, that we are only filling in the text portion of each option, not the value portion.

If Not Page.IsPostBack Then
DropDownList1.Items.Add("Georgia")
DropDownList1.Items.Add("Florida")
DropDownList1.Items.Add("Alabama")
End If

5. You can bind the DropDownList control to an ArrayList. Again, notice that we are not getting the value portion of each option.

Dim colArrayList as New System.Collections.ArrayList() 

If Not Page.IsPostBack Then 
colArrayList.Add("Georgia")
colArrayList.Add("Florida")
colArrayList.Add("Alabama")

DropDownList1.DataSource = colArrayList 
DropDownList1.DataBind() 
End If

6. The following example shows how to populate the control using a Hashtable. Now we can get both the text and value portions populated.

Dim myHashTable as new System.Collections.Hashtable()

myHashTable("GA") = "Georgia"
myHashTable("FL") = "Florida"
myHashTable("AL") = "Alabama"

For each Item in myHashTable
Dim newListItem as new ListItem()
newListItem.Text = Item.Value
newListItem.Value = Item.Key
DropDownList1.Items.Add(newListItem)
Next

7. A SortedList is a collection that stores key/value pairs (like a hashtable) but where the items are automatically sorted according to key/value. Here is an example:

Dim mySortedList as new System.Collections.SortedList
Dim Item as DictionaryEntry

mySortedList("GA") = "Georgia"
mySortedList("FL") = "Florida"
mySortedList("AL") = "Alabama"

For each Item in mySortedList
Dim newListItem as new ListItem()
newListItem.Text = Item.Value
newListItem.Value = Item.Key
DropDownList1.Items.Add(newListItem)
Next

8. Here is an example of how you might populate the control from a SQL Server database using a data reader object:

' Let's assume the connection string is stored in a session variable.
Dim strConnect as Strng
strConnect = Session("ConnectionString")

' Open the Connection
Dim Con as new System.Data.SQLClient.SQLConnection(strConnect)
Con.Open()

' SQL Statement
Dim strSQL as String
strSQL = "SELECT State_Name, State_Code FROM TableState ORDER BY State_Name"

' Command, Data Reader
Dim Com as new System.Data.SQLClient.SQLCommand(strSQL, Con)
Dim rdr as System.Data.SQLClient.SQLDataReader = Com.ExecuteReader()

' Populate the Control
While rdr.Read()
Dim newListItem as new ListItem()
newListItem.Text = rdr.GetString(0)
newListItem.Value = rdr.GetString(1)
DropDownList1.Items.Add(newListItem)
End While

Conclusion
I certainly didn't exhaust all the possibilities but I think this provides a pretty decent overview of the control, how to use it and how to get data into it. If you have any comments, corrections or other ideas, you can email me at: 

RogerMcCook@usermail.com

Roger D. McCook
McCook Software, Inc.