Question

I have the following code in my codebehind Page_Load function that sets the default selected value of a dropdownlist in detailsview based on the name of a record returned from a sql data query.

Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
        Me.Page.Title = "Editing record"

        'Perform dropdown list population operations
        Dim myDDL As DropDownList = DetailsView1.FindControl("reqCategoryDropDown")
        If Page.IsPostBack = False Then

            Dim ticket_ID As String = getDataKey(DetailsView1)
            'Fetch Category ID
            Dim sqlText As String = "SELECT TS_REQCATEGORY FROM USR_ITFAC WHERE (TS_ID = " + ticket_ID + ") "
            Dim reqDataReader As SqlDataReader = GetDataReader(sqlText)
            reqDataReader.Read()

            Dim category_ID As String = reqDataReader(0)

            'Fetch Category name and set as selected value in dropdown list
            sqlText = "SELECT TS_NAME FROM TS_SELECTIONS WHERE (TS_ID = " + category_ID + ") "
            reqDataReader = GetDataReader(sqlText)
            reqDataReader.Read()
            category_Name = reqDataReader(0)
            'myDDL.DataBind()
            myDDL.SelectedValue = category_Name
        End If

    End Sub

My problem is that when the page loads for the first time, even though I set the selected value for the dropdownlist it will not display and instead simply displays the default first name in my dropdownlist. I tried Binding my dropdownlist before and after I set the selectedvalue, it is commented out in the sample code above, but that didn’t seem to do anything.

UPDATE:
I’m setting the data source in the webform as follows:

Dropdownlist:

<asp:DropDownList DataSourceID="ReqCategoryData" DataTextField="ReqCategory" DataValueField="ReqCategory"
                                ID="reqCategoryDropDown" runat="server" AppendDataBoundItems="true" AutoPostBack="true">                                                            
                            </asp:DropDownList>

Connects to data source a few lines down:

<asp:SqlDataSource ID="ReqCategoryData" runat="server" ConnectionString="<%$ ConnectionStrings:TTPRODReportsQuery %>"
        SelectCommand="SELECT TS_NAME AS ReqCategory FROM dbo.TS_SELECTIONS WHERE (TS_FLDID = 5299 AND TS_STATUS = 0) ORDER BY TS_NAME">
        </asp:SqlDataSource>

UPDATE_2:
Ok, so I implemented he SQLDataSource programmatically in the code-behind under the Page_Init function as follows:

Protected Sub Page_Init(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Init
        DetailsView1.DefaultMode = DetailsViewMode.Edit

        ''Setup DropDownList SqlDataSource
        ddlDataSource.ID = "ReqCategoryData"
        Page.Controls.Add(ddlDataSource)
        ddlDataSource.ConnectionString = ConfigurationManager.ConnectionStrings("TTPRODReportsQuery").ConnectionString
        ddlDataSource.SelectCommand = "SELECT TS_NAME AS ReqCategory FROM dbo.TS_SELECTIONS WHERE (TS_FLDID = 5299 AND TS_STATUS = 0) ORDER BY TS_NAME"
        Dim args As New DataSourceSelectArguments
        ddlDataSource.Select(args)
        ddlDataSource.DataBind()

    End Sub

After which I set attempt to set the selected value of the dropdownlist as above. The page is still not setting the selected value.

Answer 1

Perhaps check these items:

• ensure you’re calling myDDL.DataSource = reqDataReader or some other form of setting the DataSource of your dropdownlist.
• ensure the dropdownlist has its DataTextField and DataTextField set properly. This could be in code-behind or in markup.
• The 0’th index of reqDataReader — are you sure that’s the intended ordinal for the DataValueField?

Perhaps something like this:

With myDDL
    .DataTextField = "CategoryName"
    .DataValueField = "CategoryID" ' or perhaps CategoryName as your value.
    .DataSource = reqDataReader
    .DataBind()
    .SelectedValue = category_Name ' Name or ID; depends on what was set as DataValueField
End With

DataBinding – Code-Behind vs. Markup DataSources

Consider choosing one style of binding your dropdownlist – in code-behind or with a markup SqlDataSource. Having both generates confusion on which bind wins – the code-behind or the datasource. I think it’s the SqlDataSource in this case.

Consider removing the SqlDataSource from out of the markup, and create a method in code-behind whose sole purpose is to create the data binding. This is the only place where the binding should happen. If you ever need to track down a defect or enhance your logic, it’s the only one place to visit.

Private Sub BindMyDropDown(Optional ByVal selectedValue as String)
    With myDDL
        .DataTextField = "CategoryName"
        .DataValueField = "CategoryID" ' or perhaps CategoryName as your value.
        .DataSource = LoadTicketReqCategory(TicketID)
        .DataBind()
        .SelectedValue = selectedValue ' Name or ID; depends on what was set as  DataValueField
    End With

End Sub

From your Page_Load(), check for IsPostBack() and call this method when you aren’t posting back.