ItemCommand event not firing for DataList

2019-09-18 02:10发布

I've inherited a VB.Net application that I'm testing and the ItemCommand event is not firing... It is a VB.Net 4.0 application.

I've searched the web for this error and doubhle checked the code in the application.

I know this event is supposed to fire on a postback after the page_load event. However, when I click on the ImageButton (to force a postback and hopefully execute the ItemCommand event), the Page.IsPostBack property is still set to FALSE, thereby never being able to execute the ItemCommand event. I don't know why this property would still be set to FALSE. Evidently, I need a way to signify to the page that a postback is occurring. The ImageButton should take care of this since it has the runat="server" tag.

Below are the code snippets. Can someone please inform me what I would need to do in order to fire the Item command? What I said above is true, I believe. I don't know why after the page loads and I press the ImageButton that the property would still be set to FALSE.

HTML

<asp:DataList ID="lstReferrals" runat="server" DataKeyField="ReferringAffiliateID"
    OnItemCommand="lstReferrals_ItemCommand" CellPadding="4" Summary="Referral Design Table"
    Width="800"><ItemTemplate>
        <tr class="small" bgcolor="#FFFFFF">
            <td>
                <asp:ImageButton ID="btnSelect" AlternateText="Select" ImageUrl='<%# NodeImage(1) %>'
                    CommandName="select" runat="server" />CODE BEHINDPrivate Sub Page_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load



'Put user code to initialize the page here
        If Not (Request.Params("ItemIndex") Is Nothing) Then
            itemIndex = Int32.Parse(Request.Params("ItemIndex"))
        Else
            itemIndex = Convert.ToInt32(Null.SetNull(itemIndex))
        End If


        If Not Page.IsPostBack Then
            LoadReferrals()

            If Not Null.IsNull(itemIndex) Then
                lstReferrals.SelectedIndex = itemIndex
                LoadReferrals()
            End If
        End If


    End Sub



Protected Sub lstReferrals_ItemCommand(ByVal source As Object, ByVal e As System.Web.UI.WebControls.DataListCommandEventArgs) Handles lstReferrals.ItemCommand

        Try
            errormessage.Visible = False
            ' Determine the command of the button (either "select" or "collapse")
            Dim command As String = CType(e.CommandSource, ImageButton).CommandName



            ' Update asp:datalist selection index depending upon the type of command
            ' and then rebind the asp:datalist with content
            Select Case command
                Case "collapse"
                    lstReferrals.SelectedIndex = -1
                    LoadReferrals()
                Case "select"
                    lstReferrals.SelectedIndex = e.Item.ItemIndex
                    LoadReferrals()

1条回答
狗以群分
2楼-- · 2019-09-18 02:41

I needed to add an event handler in the page_load method which would set the OnItemCommand event to fire:

lstProducts.ItemCommand += new DataListCommandEventHandler(lstProducts_ItemCommand);

In C#, I've noticed sometimes that the aspx file doesn't always trigger an event firing. For instance, if you have OnItemCommand="abc", it doesn't neccessarily fire (for whatever reason). If this is the case, you should force asp.net to add the event handler in the code behind as stated above.

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