Question

I have a nested repeater with a delete button in it. This button deletes a student from a group. but when I press the delete button it just goes through the nested repeater again and I get:

Invalid postback or callback argument.

Stack Trace:

[ArgumentException: 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.]
System.Web.UI.ClientScriptManager.ValidateEvent(String uniqueId, String argument) +9714590
System.Web.UI.Control.ValidateEvent(String uniqueID, String eventArgument) +111
System.Web.UI.WebControls.ImageButton.RaisePostBackEvent(String eventArgument) +29
  System.Web.UI.WebControls.ImageButton.System.Web.UI.IPostBackEventHandler.RaisePostBackEvent(String eventArgument) +10
System.Web.UI.Page.RaisePostBackEvent(IPostBackEventHandler sourceControl, String eventArgument) +13
System.Web.UI.Page.RaisePostBackEvent(NameValueCollection postData) +35
System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +1724

my asp.net file:

<!-- Begin modal -->
<asp:Repeater ID="RepeaterModal" OnItemDataBound="RepeaterModal_ItemDataBound" runat="server">
    <HeaderTemplate>
    <div id="modal">
    </HeaderTemplate>
    <ItemTemplate> 
        <div id="dialog<asp:Literal ID='ltlModalNumber' runat='server' />" class="window">
            <div class="contents">
                <h3>Students in group <asp:Literal ID="ltlModalGroup" runat="server" /></h3>
                <ul>
                <asp:Repeater ID="repeaterModalStudentList" Runat="server">
                    <ItemTemplate>
                        <li class="modalStudent"><%# Eval("Name") %></li>
                        <li class="modalStudentClassDelete">
                            <asp:ImageButton ID="imgDeleteStudent" runat="server" ImageUrl="styles/img/icons/2.png" CommandName="deleteStudent" OnClick="btnDeleteStudent_Click" ToolTip="Delete this student" />
                        </li>
                    </ItemTemplate>
                </asp:Repeater>
                </ul>                       

                <a href="#" class="close">Close</a>
            </div>
        </div>
    </ItemTemplate> 
    <FooterTemplate>
    </div>
    </FooterTemplate>

</asp:Repeater>
<!-- End modal -->

In my code behind file I do:

//A field 
int r = 0;

//Populates the table with the list of groups.
RepeaterModal.DataSource = listOfGroups;
RepeaterModal.DataBind();

listOfGroups contains a list with Group objects that contain a group_Id, name, code, Students object with strings for the name of the students.

//Repeater methode to put the values in the correct labels of the modal window
public void RepeaterModal_ItemDataBound(Object Sender, RepeaterItemEventArgs e) {
    //Execute the following logic for Items and Alternating Items.
    if (e.Item.ItemType == ListItemType.Item || e.Item.ItemType == ListItemType.AlternatingItem) {
        ((Literal)e.Item.FindControl("ltlModalNumber")).Text = ((Groups)e.Item.DataItem).Group_Id.ToString();
        ((Literal)e.Item.FindControl("ltlModalGroup")).Text = ((Groups)e.Item.DataItem).Code.ToString();    

        //Fill the repeater inside the repeater with the students name
        Repeater repeaterModalStudentList = ((Repeater)e.Item.FindControl("repeaterModalStudentList"));
        repeaterModalStudentList.DataSource = ((Groups)e.Item.DataItem).Students;
        repeaterModalStudentList.DataBind();

        ImageButton imgDeleteStudent = repeaterModalStudentList.Items[0].FindControl("imgDeleteStudent") as ImageButton;

        if (imgDeleteStudent != null) {
                imgDeleteStudent.CommandArgument = ((Groups)e.Item.DataItem).Students[r].Student_Id.ToString();
                r++;
        }
    }
}

protected void btnDeleteStudent_Click(object sender, EventArgs e) {     
    ImageButton b = (ImageButton)sender;
    string value = b.CommandArgument;

    Students student = new Students();
    student.DeleteStudent(int.Parse(value));

    Response.Redirect(Request.RawUrl);
}

What am I missing or doing wrong that I keep getting that error? adding EnableEventValidation is not the solution. It’s something with the commandArgument.

Edit

Lol, Added if(!IsPostBack), ain’t getting the error anymore. But there isn’t a value in the CommandArgument.

Answer 1

You are assigning the CommandArgument, but your method is btnDeleteStudent_Click

Update:

//Repeater methode to put the values in the correct labels of the modal window 
public void RepeaterModal_ItemDataBound(Object Sender, RepeaterItemEventArgs e) { 
    //Execute the following logic for Items and Alternating Items. 
    if (e.Item.ItemType == ListItemType.Item || e.Item.ItemType == ListItemType.AlternatingItem) { 
        ((Literal)e.Item.FindControl("ltlModalNumber")).Text = ((Groups)e.Item.DataItem).Group_Id.ToString(); 
        ((Literal)e.Item.FindControl("ltlModalGroup")).Text = ((Groups)e.Item.DataItem).Code.ToString();     

        //Fill the repeater inside the repeater with the students name 
        Repeater repeaterModalStudentList = ((Repeater)e.Item.FindControl("repeaterModalStudentList")); 
        repeaterModalStudentList.DataSource = ((Groups)e.Item.DataItem).Students; 
        repeaterModalStudentList.DataBind(); 
        repeaterModalStudentList.ItemDataBound += repeaterModalStudentList_ItemDataBound; 
    } 
} 

//Repeater methode to put the values in the correct labels of the modal window 
public void repeaterModalStudentList_ItemDataBound(Object Sender, RepeaterItemEventArgs e) { 
    //Execute the following logic for Items and Alternating Items. 
    if (e.Item.ItemType == ListItemType.Item || e.Item.ItemType == ListItemType.AlternatingItem) {       

        ImageButton imgDeleteStudent = repeaterModalStudentList.Items[0].FindControl("imgDeleteStudent") as ImageButton; 

        if (imgDeleteStudent != null) { 
            imgDeleteStudent.CommandArgument = ((Student)e.Item.DataItem).Student_Id.ToString(); 
        } 
    } 
} 


protected void btnDeleteStudent_Click(object sender, EventArgs e) {  
    ImageButton btn = (ImageButton)sender; 
    int studentId = (int)btn.CommandArgument; 

    Students student = new Students(); 
    student.DeleteStudent(studentId); 

    Response.Redirect(Request.RawUrl); 
}