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Can I bind a drop down list selectedvalue in C# code behind?

Posted on 2009-06-30
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Last Modified: 2013-12-17
I have written the attached code within the onitemupdating event of my asp.net 3.5 listview control. I am attempting to update an item in my backend database which is bound to a drop down list control in the edititemtemplate of my frontend listview control but by using C#. Currently no errors are flagged but my update is now occurring? My e.NewValues reference doesn't seem to be registering although I can see that the correct value seems to be getting attached in debug?

Thanks.
Frontend drop down list control within my listviews edititemtemplate:
 
<asp:DropDownList 
    ID="InterviewerEditDDL" 
    runat="server" 
    DataSourceID="InterviewerEditDataSource" 
    DataTextField="InterviewerName" 
    DataValueField="InterviewerID" 
    CssClass="ddlTxtBoxInterviewer">
</asp:DropDownList>
<asp:LinqDataSource 
    ID="InterviewerEditDataSource" 
    ContextTypeName="HRsystemDataContext" 
    TableName="ApplicantInterviewers" 
    runat="server" 
    onselecting="InterviewerEditDataSource_Selecting" />
 
OnItemUpdating event of my listview (lvInterviewers):
 
protected void lvInterviewers_ItemUpdating(object sender, ListViewUpdateEventArgs e)
    {
        DropDownList ddlEditInterviewerID = (DropDownList)lvInterviewers.Items[e.ItemIndex].FindControl("InterviewerEditDDL");
 
        e.OldValues["InterviewerID"] = ddlEditInterviewerID.SelectedValue;
 
        if (ddlEditInterviewerID.SelectedValue != "20")
        {
            e.NewValues["InterviewerID"] = ddlEditInterviewerID.SelectedValue;
        }
    }

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Question by:Shepwedd
  • 2
3 Comments
 
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Expert Comment

by:nikege
ID: 24749249
Actually I don't understand how are you binding DropDownList's SelectedValue.
try this:
<asp:DropDownList 
    ID="InterviewerEditDDL" 
    runat="server" 
    DataSourceID="InterviewerEditDataSource" 
    DataTextField="InterviewerName" 
    DataValueField="InterviewerID" 
    CssClass="ddlTxtBoxInterviewer"
    SelectedValue='<%# Eval("InterviewID")%>'>
</asp:DropDownList>

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Author Comment

by:Shepwedd
ID: 24752551
nikege,

When I add:

SelectedValue='<%# Eval("InterviewerID")%>'

I get the error: "HttpException was unhandled by user code"? That's why I am attempting to bind my drop down lists selectedvalue in code behind (onitemupdating event) but my update doesn't seem to occur?

Thanks.
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Accepted Solution

by:
nikege earned 500 total points
ID: 24752797
I am surprised that you got an error when you bind it using declarative syntax. If you can provide stack trace I will be able to answer why it happens.
But about binding from codebehind - Sure you can bind drop down from the codebehind. You should do it in ItemDataBound or DataBound events of ListView. Look at the code bellow. It shows how you can use ItemDataBound event.
Also look at this article http://msdn.microsoft.com/en-us/library/ms178366.aspx. In the end of article you can find 'Using Binding for a Lookup Table ' section.
<%@ Page language="C#" %>
 
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
 
<script runat="server">
 
  protected void ContactsListView_ItemDataBound(object sender, ListViewItemEventArgs e)
  {
    if (e.Item.ItemType == ListViewItemType.DataItem)
    {
      // Display the e-mail address in italics.
      Label EmailAddressLabel = (Label)e.Item.FindControl("EmailAddressLabel");
      EmailAddressLabel.Font.Italic = true;
    }
  }
 
</script>
 
<html xmlns="http://www.w3.org/1999/xhtml" >
  <head id="Head1" runat="server">
    <title>ListView ItemDataBound Example</title>
  </head>
  <body style="font: 10pt Trebuchet MS">
    <form id="form1" runat="server">
 
      <h3>ListView ItemDataBound Example</h3>
 
      <asp:ListView ID="ContactsListView" 
        DataSourceID="ContactsDataSource" 
        ConvertEmptyStringToNull="true"        
        OnItemDataBound="ContactsListView_ItemDataBound"
        runat="server">
        <LayoutTemplate>
          <table cellpadding="2" width="680px" border="0">
            <tr style="background-color: #ADD8E6" runat="server">
                <th runat="server">First Name</th>
                <th runat="server">Last Name</th>
                <th runat="server">E-mail Address</th>
            </tr>
            <tr runat="server" id="itemPlaceholder" />
          </table>
          <asp:DataPager runat="server" ID="PeopleDataPager" PageSize="12">
            <Fields>
              <asp:NumericPagerField ButtonCount="10" /> 
            </Fields>
          </asp:DataPager>
        </LayoutTemplate>
        <ItemTemplate>
          <tr style="background-color: #CAEEFF" runat="server">
            <td>
              <asp:Label ID="FirstNameLabel" runat="server" Text='<%#Eval("FirstName") %>' />
            </td>
            <td>
              <asp:Label ID="LastNameLabel" runat="server" Text='<%#Eval("LastName") %>' />
            </td>
            <td>
              <asp:Label ID="EmailAddressLabel" runat="server" Text='<%#Eval("EmailAddress") %>' />
            </td>
          </tr>
        </ItemTemplate>
      </asp:ListView>
 
      <!-- This example uses Microsoft SQL Server and connects      -->
      <!-- to the AdventureWorks sample database. Use an ASP.NET    -->
      <!-- expression to retrieve the connection string value       -->
      <!-- from the Web.config file.                                -->
      <asp:SqlDataSource ID="ContactsDataSource" runat="server" 
        ConnectionString="<%$ ConnectionStrings:AdventureWorks_DataConnectionString %>"
        SelectCommand="SELECT FirstName, LastName, EmailAddress FROM Person.Contact">
      </asp:SqlDataSource>
 
    </form>
  </body>
</html>

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