Question

I have a page which lists a bunch of items in a datagrid.

Each item has a cooresponding remove link button, which removes the item from the list. In my event handler — where the item is deleted — I do a check to see if the item is the last item in the list. If it is the last item, I don’t do a delete, but send an alert box telling the user that the item cannot be deleted. I am unsure how to get C# to trigger this alert box.

My code looks like the following:

In my aspx, I have a datagrid with various Link Buttons. Snippet of code as shown:

<ItemTemplate>
    <asp:LinkButton runat="server" ID="Remove"
                OnCommand="lnkRemove_Command" CommandArgument='<%# Eval("Id") %>
                OnClientClick="return false;">
    </asp:LinkButton>
</ItemTemplate>

In my code behind, my event handler looks like such:

   private List<MyItem> _items;

   protected void lnkRemove_Command(object sender, CommandEventArgs e)
   {
      int ID = Convert.ToInt32(e.CommandArgument);
      MyItem item = MyItem.GetItemByID(id); //This gets the item cooresponding to the ID
      if (_items.Count != 1) 
      {
          //code to delete item   
      }
      else
      {
           //Generate an alert box to tell the user that this item cannot be deleted.
           //I have tried the following two lines of commented code, which didn't work for me
           //Response.Write(@"<script language='javascript'>alert('HERE');</script>");
           //Page.ClientScript.RegisterStartupScript(this.GetType(), "hwa", "alert('Hello World');", true);

      }
   }

In addition, it may be important to note that in my Page_Load, I already do a Context.RegisterResource(this, StyleSheet, Script). In other words, I have working JavaScript and CSS, which cooresponds with this code for other features of this page in MyFile.js

If possible, I would like to create a JS function in MyFile.js where I already have js functions which are triggered by various OnClientClicks, etc…

Is it possible to do something like this:

in MyFile.js

var GetAlertMessage = function()
{
    alert("Can't delete this item");
}

and call this function in my C# function that I listed above?

Thanks in advance for the help.

Answer 1

You should treat this like any other validation routine. There should be a client-side validation function and a server-side validation function.

Client Side Validation

on each delete-able item, add an onclick="ValidateDeletion();" and class="deleteable-item"

function ValidateDeletion()
{
    var itemCount = $(".deleteable-item").length;
    if(itemCount == 1)
    {
        alert("Sorry, you cant delete this item.")
        return false;
    }
    else
    {
        //let it pass through
    }

}