Firing an automatic update from DropDownList control within a ListView - asp.net

Question

I'm an asp.net newbie. Basically, I have a DropDownList within and EditItemTemplate within a ListView. When a new item is selected in the drop down, the user would like to NOT have to click the LinkButton for update, but have the update happen automatically. I've experimented with the OnSelectedIndexChanged="ddlrank_itemChanged" using code behind, as well as OnChange="MyFoo()" in javascript, but the details of what to do are beyound me.
I hope I am including the code sample correctly. Any suggestions will be greatly appreciated. Thanks.
<asp:ListView ID="ListView1" runat="server" DataKeyNames="rankingID" DataSourceID="SqlDataSource1" OnItemUpdated="ListView1_Item_Updated">
<LayoutTemplate>
<table cellpadding="2" width="640px" border="1" runat="server" id="tblRankings">
<tr id="Tr1" runat="server">
<th id="Th1" runat="server">Action</th>
<th id="Th3" runat="server">Rank</th>
<th id="Th4" runat="server">Committee name</th>
<th id="Th5" runat="server">Committee type</th>
</tr>
<tr runat="server" id="itemPlaceholder" />
</table>
<asp:DataPager runat="server" ID="RankingDataPager" PageSize="100">
<Fields>
<asp:NextPreviousPagerField ShowFirstPageButton="true" ShowLastPageButton="true"
FirstPageText="|<< " LastPageText=" >>|"
NextPageText=" > " PreviousPageText=" < " />
</Fields>
</asp:DataPager>
</LayoutTemplate>
<ItemTemplate >
<tr id="Tr2" runat="server">
<td>
<asp:LinkButton ID="EditButton" runat="Server" Text="Edit" CommandName="Edit" />
</td>
<td valign="top">
<asp:Label ID="RankLabel" runat="Server" Text='<%#Eval("rank") %>' />
</td>
<td valign="top">
<asp:Label ID="CommitteeNameLabel" runat="Server" Text='<%#Eval("committeename") %>' />
</td>
<td valign="top">
<asp:Label ID="CommitteeTypeLabel" runat="Server" Text='<%#Eval("committeetype") %>' />
</td>
</tr>
</ItemTemplate>
<EditItemTemplate >
<tr style="background-color: #ADD8E6">
<td>
<asp:LinkButton ID="UpdateButton" runat="server" CommandName="Update" Text="Update" />
<asp:LinkButton ID="CancelButton" runat="server" CommandName="Cancel" Text="Cancel" />
</td>
<td>
<asp:DropDownList ID="ddlrank"
DataSourceID="sdsrank"
DataValueField="vchvalue"
DataTextField="vchvalue"
OnSelectedIndexChanged="ddlrank_itemChanged"
OnChange="MyFoo()"
SelectedValue='<%# Bind("rank") %>' runat="server" >
</asp:DropDownList>
</td>
<td>
<asp:TextBox ID="CommitteeNameTextBox" runat="server" Enabled="false" ReadOnly="true" Text='<%#Bind("committeename") %>'
MaxLength="200" /><br />
</td>
<td>
<asp:TextBox ID="CommitteeTypeTextBox" runat="server" Enabled="false" ReadOnly="true" Text='<%#Bind("committeetype") %>'
MaxLength="20" /><br />
</td>
</tr>
</EditItemTemplate>
</asp:ListView>

Answer 1

I think you are missing AutoPostBack="true" on your dropdownlist property. Hope it helps.

Answer 2

You're headed in the right direction. You can use "OnSelectedIndexChanged", or you can create a function in your codebehind page that handles the SelectedIndexChanged event. Either way, when the user makes a selection from the dropdown, you get a postback and that function is executed. In the function you can do whatever you want. In a case like this that might mean checking what the selected value is and setting other values on the screen based on the new selection. When the function exits, a new screen is sent to the user's browser with any updated data.

Answer 3

Thanks for the replies, they helped direct and refine my internet searching!
I finally found a simple solution.
It just requires two lines of code in the OnSelectedIndexChanged code-behind function defined on the dropdownlist:
protected void ddlrank_itemChanged(object sender, EventArgs e)
{
ListViewDataItem item = (ListViewDataItem)((DropDownList)sender).Parent;
ListView1.UpdateItem(item.DisplayIndex, false);
}