How to get values in code behind from a nested DropDownList Control?

Question

User426001450 posted

Hello to all !!

I do have a DropDownList nested in a DataList. When DataList displays on the page, if it has  20, 50, 75 or n records, it is obvious that there are going to be many ddl display on the DataList, one for each row. How may I access from code behind the particular ddl that user changes in order for me to get the new values?

When the text or value changes I would like to get in code behind the item index, value, text, and AutoNumber of the particular ddl and record.

I'm using Visual Basic, if you are willing to help please provide code in VB, thanks

Here is my code for the ddl:

<asp:DataList 
      ID="DogRosterApprovedForShowBallotDataList" 
      runat="server"
      GridLines="Both"
      DataSourceID="DogRosterApprovedForShowBallotSqlDataSource"
      DataKeyNames="DogAutoNumber, UserName, TDogShowStatus, AutoNumber, TDogShowBallotStatus"     >

          <AlternatingItemStyle BackColor="#FFFBD6" />
          <HeaderStyle BackColor="#00693E" ForeColor="White" />

        <HeaderTemplate>
          Official dog show voting ballot <br />
        </HeaderTemplate>
 
         <ItemTemplate>  
             
             <br />
             Performer # : <%# Container.ItemIndex + 1 %>
             <br /><br />

                       
             First Name / Click for info: <i style="color:#00693E"> <asp:HyperLink ID="OfficialListHyperLink" Target="_blank" Text='<%# Eval("TPerformerFirstName") %>' runat="server" NavigateUrl='<%#String.Concat("~/TalentShow/PerformerProfilePage.aspx?UserName=", Convert.ToString(Eval("UserName"))) %>' >  </asp:HyperLink></i>
             <br />
             
             Last Name : <i style="color:#00693E"><%# Eval("TPerformerLastName") %></i>
             <br />

             Dog Name : <i style="color:#00693E"><%# Eval("TDogStageName") %></i>
             <br /><br />
                
             

             Your selection : 
             <asp:DropDownList ID="SelectionForVotingDropDownList" AutoPostBack="true"  runat="server"   >
                                  
                 <asp:ListItem Selected="True" Value="Select">-- Select place --</asp:ListItem>
                 <asp:ListItem Value="First place"> First place </asp:ListItem>
                 <asp:ListItem Value="Second place"> Second place </asp:ListItem>
                 <asp:ListItem Value="Third place"> Third place </asp:ListItem>

            </asp:DropDownList>
                          
         <br /><br />
         </ItemTemplate> 
            
            <FooterTemplate>
                <%# DogRosterApprovedForShowBallotDataList.Items.Count %> Record(s) returned
            </FooterTemplate>
            
      </asp:DataList>

Thanks to all for helping !!

Answer 1

User-1716253493 posted

    Protected Sub DropDownList1_SelectedIndexChanged(sender As Object, e As EventArgs) Handles DropDownList1.SelectedIndexChanged
        Dim ddl As DropDownList = CType(sender, DropDownList)
        Dim item As DataListItem = CType(ddl.NamingContainer, DataListItem)
        Dim idx As Integer = item.ItemIndex
        Dim auton As Integer = DataList1.DataKeys(idx)

    End Sub

Answer 2

User426001450 posted

Thanks for your help.

Your code is pretty close to what I had but still is not working. There are two things that are giving me problems: 1) DataKeys in your code, there are none  for DataList, so I changed that to the right one that should be DataKeyField. But it is not working either. 

2) Since I have more than one DataKeyField, I think that not only the idx but the DataKeyField name should be include in the code.. So, I made the following changes but it is not working. Any thoughts?

Changes:

        Dim ddl As DropDownList = CType(sender, DropDownList)
        Dim item As DataListItem = CType(ddl.NamingContainer, DataListItem)
        Dim idx As Integer = item.ItemIndex
        Dim autonumber As Integer = DataList1.DataKeyField("AutoNumber", idx).ToString

Thanks for your help again

Answer 3

User-1716253493 posted

AFAIK, DataList don't have multiple datakeys

You can use hiddenfeild or other control, or use gridview instead

Answer 4

User426001450 posted

Ok, I understand what you are saying but if that is the case, it should works when the dataKeyField is holding one value only and it is not.

This is what I have just for testing and for trying to understand how this control works:

For the DataList I have:

<asp:DataList 
      ID="DogsRosterApprovedForShowBallotDataList" 
      runat="server" 
      DataSourceID="DogsRosterApprovedForShowBallotSqlDataSource" 
      DataKeyFields ="AutoNumber"   >

As you can see, there is only one value in the DataKeyField. And this is my code behind:

        Dim ddl As DropDownList = CType(sender, DropDownList)
        Dim item As DataListItem = CType(ddl.NamingContainer, DataListItem)
        Dim idx As Integer = CType(item, DataListItem).ItemIndex
        Dim keyAutoNumber As String = DogsRosterApprovedForShowBallotDataList.DataKeyField(idx).ToString
        Label2.Text = "This is the autonumber for this record: " + keyAutoNumber

But, it is not working even with one value, What is going on, what is the purpose of the DataKeyFied. I'm just trying to understand this control. Once again thanks for your help.

Thanks

Answer 5

User-1716253493 posted

Check and try this

        <asp:DataList ID="DataList1" runat="server" DataKeyField="AutoNumber">
        </asp:DataList>

DataKeyField without "s"

Dim AutoNumber As Integer = DataList1.DataKeys(idx)

Answer 6

User426001450 posted

This is completely stupid, there is lot nonsense and the one to blame here is msft.

1) The field once created in the DataList look like this: DataKeyField="AutoNumber". There is no other option like DataKey, Datakeys, Datakeyfields or whatever. This is the only option. However in the code behind, we cannot use the same word ‘DataKeyField’ to retrieve the value, but DataKeys instead, this is stupid and confusing. 

2) In the code behind, the following will work to retrieve the value:

 DataList.DataKeys(idx). But you need all the following code to find the index:

Dim ddl As DropDownList = CType(sender, DropDownList)

Dim item As DataListItem = CType(ddl.NamingContainer, DataListItem)

Dim idx As Integer = CType(item, DataListItem).ItemIndex 

3) Another stupidity or limitation is that DataKeyField can only hold one value. I  added another value like : DataKeyField="AutoNumber, UserName". But I couldn’t retrieve anything and an error was displayed. This is the error:  'System.Data.DataRowView' does not contain a property with the name 'AutoNumber, UserName'. 

So it can hold the AutoNumber or the UserName value but not both. This shouldn’t be because these limitations force us to enter more lines of code to get other values and good programing is about less coding. 

Another stupid thing is that if it can only hold one value why I cannot retrieve it in the code behind as ‘DataKey’ without the ‘s’ but it has to be as DataKeys. Nonsense. And once again should be DataKeyField instead anyway for the retrieving. I already mentioned that. But if your code is  DataList.DataKeyField(idx) to retrieve value you will get nothing.      

Well I got fed up with this control, enough is enough. Thanks for your help.

 

Answer 7

User426001450 posted

My final suggestion is to use a HiddenField to find all values even though there is more coding involve there is not other way. In order to find how to do it you can take a look at this link: https://forums.asp.net/t/1684637.aspx

Thanks

Answer 8

User-1716253493 posted

Hi vstorpedo,

Each record has own datakey ie ID Or AutoNumber or DogAutoNumber

If you get the key value of the record, you dont need another value as criteria

ie : delele from tbl where AutoNumber=100 is enough

Answer 9

User426001450 posted

AFAIK, DataList don't have multiple datakeys

You can use hiddenfeild or other control, or use gridview instead

Thank you oned_gk, you are a great guy, thanks for your help. I picked this answer with the hiddenfield as the best solution for my question. You are one of the best here. Thanks