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Here is a code tag code of asp.net and there is a Image button where i want code on click event for download item i try to code on click event but it was not working

    <asp:ListView runat="server" ID="ListView1" GroupItemCount="1">
                <LayoutTemplate> 
                <div>
                        <asp:PlaceHolder runat="server" ID="groupPlaceHolder" />
                    </div>              
                </LayoutTemplate>
                <GroupTemplate>   
                   <div style="clear: both;">
                        <asp:PlaceHolder runat="server" ID="itemPlaceHolder" />
                    </div>                       
                </GroupTemplate>
                <ItemTemplate>
                <div style="margin-left: 20px; border: 2px rgba(255, 102, 0, 0.36) 
dotted; width: 900px; padding: 10px;">
    <video src='<%# "Handler.ashx?id=" + Eval("id") %>' 
width="900" height="400" controls="" preload=""></video>
    </div>    
          <div style="width:950px; height:90px;" align="right">
              <asp:ImageButton ID="ImageButton1" 
ImageUrl="images/download-button.jpg" runat="server" width="230px"/> 
      </div>
                </ItemTemplate>            
                <GroupSeparatorTemplate>
                    <div style="clear:both"></div> 
                </GroupSeparatorTemplate>
                <EmptyDataTemplate>
                </EmptyDataTemplate>
            </asp:ListView>

Here is a c# Private code class on same page that is

Private void Download(string ID)
{
  some code here for download
}

please let me know how can i code on image button for download a file.

Error:

Invalid postback or callback argument. 

Event validation is enabled using 
<pages enableEventValidation="true"/> in configuration or 
<%@ Page EnableEventValidation="true" %> in a page.  
For security purposes, this feature verifies that arguments to 
postback or callback events originate from the server 
control that originally rendered them.  If the data is valid and expected, use the    ClientScriptManager.RegisterForEventValidation method in order to 
register the postback or callback data for validation.
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when you say the click event was not working - you mean it did not fire? in which case, did you try causesvalidation = "false"? –  user2377420 Jun 8 '13 at 15:02
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2 Answers

up vote 0 down vote

button control is inside listview why dont you give it Command-name and then run the Item-command of the listview. e.g

Assign the CommandName property of the Image button and then in ItemCommand of listview write

<asp:ImageButton ID="ImageButton1" ImageUrl="images/download-button.jpg" 
runat="server" width="230px" CommandName ="Download"/> 

if (e.CommandName = "Download")
{

WriteYour Code here..

 }
share|improve this answer
 
I'm getting this error Invalid postback or callback argument. Event validation is enabled using <pages enableEventValidation="true"/> in configuration or <%@ Page EnableEventValidation="true" %> in a page. For security purposes, this feature verifies that arguments to postback or callback events originate from the server control that originally rendered them. If the data is valid and expected, use the ClientScriptManager.RegisterForEventValidation method in order to register the postback or callback data for validation. –  Vikas Jun 9 '13 at 3:06
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up vote 0 down vote

for accessing that button in listview you should use item command event like this:

protected void ListView1_ItemCommand(object sender, ListViewCommandEventArgs e)
    {
        if (e.CommandName == "EditRecord")
        {

        }
        else if (e.CommandName == "DeleteRecord")
        {

        }
    }

you can also use the onclick event of button but that's not recommended way of doing. you have to manually add the OnClick="ImageButton1_OnClick()" in button markup and then put the event manually in the code behind file 

protected void ImageButton1_OnClick(object sender, EventArgs e)
{

}

Regarding your Invalid postback or callback argument error, some html is generated by some control. you have to overview your whole webform, and register any script you are using under scriptmanager. or if nothing works out you can disable this check. <%@ Page EnableEventValidation="false" %>

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