Please what's causing this “Index was out of range Must be non-negative… error”?

Question

Please can someone really tell me what's wrong with this code that I'm having this error:

System.ArgumentOutOfRangeException was caught
Message=Index was out of range. Must be non-negative and less than the size of the collection.
Parameter name: index

int index = Int32.Parse(e.CommandArgument.ToString());
long Id = long.Parse(gvGrid.DataKeys[index][0].ToString());
var stuobj = ctx.stockUnits.SingleOrDefault(st => st.ID == Id);

                        if (stuobj != null)
                            this.txtStockUnit.Text = stuobj.NAME;

                        ViewState["Id"] = Id; 

In the mark up (Designer source) this is what I have:

<asp:GridView ID="gvGrid" runat="server" 
            OnPageIndexChanging = "gvGrid_PageIndexChanging" AutoGenerateColumns="False" 
            BackColor="White" CssClass = "mGrid"  DataKeyNames ="Id,NAME"
                OnRowCommand="gvGrid_RowCommand"

...<Columns>

        <asp:BoundField DataField="NAME" HeaderText="STOCK UNIT NAME" HeaderStyle-CssClass="Headerhodder"
                        FooterStyle-CssClass="Headerhodder" ItemStyle-HorizontalAlign="Left"  HeaderStyle-HorizontalAlign="Left" 
                        ItemStyle-VerticalAlign="Middle" />
           <asp:TemplateField HeaderStyle-CssClass="Headerhodder" FooterStyle-CssClass="Headerhodder"
                        ItemStyle-HorizontalAlign="Center"  ItemStyle-Width="50px"
            ItemStyle-VerticalAlign="Middle">
            <ItemTemplate>

                            <asp:ImageButton ID="imgEdit" runat="server" ImageUrl="~/img/pencil.png" CommandName="EditStockUnit" CommandArgument ='<%# Container.DataItemIndex %> '
                            AlternateText="Edit Stock Unit" ToolTip="Edit Stock unit record"  CausesValidation="false" />

Is there anything missing here? Thanks for the assistance.

Answer 1

This error occurs when you try to access an element of a collection which is outside of its bounds (e.g. element 10 of a 9 element array). I'm not particularly familiar with the language you are using, but the code below looks like it uses a value which can be outside of the range of the collection gvGrid.DataKeys.

int index = Int32.Parse(e.CommandArgument.ToString());
long Id = long.Parse(gvGrid.DataKeys[index][0].ToString());

If you perform some sort of sanity check e.g. if( index < count ) on the index which is passed in to make sure that it is not greater than the last indexable element, you shouldn't get the exception.

Answer 2

It worked perfectly, just use the following line instead

string Id = gvGrid.DataKeys[index %= gvGrid.PageSize][0].ToString();

So have enjoy your coding....