I am using a webdatagrid to display information from a SQL Server Database.  I have a template column with a 'Delete' button in it, which allows the user to delete a record.

My webdatagrid markup is as follows:

<ig:webdatagrid id="wdgSamples" runat="server" AutoGenerateColumns="False" StyleSetName="Default" width="475px"
    DataKeyFields="Recnum" EnableViewState="true" EnableDataViewState="true" >
    <Columns>
        <ig:BoundDataField DataFieldName="SampleDate" Key="SampleDate" Width="90px" >
            <Header Text="Sample Date" />
        </ig:BoundDataField>
        <ig:BoundDataField DataFieldName="AAS" Key="AAS" Width="135px" >
            <Header Text="Average Aphid Score" />
        </ig:BoundDataField>
        <ig:BoundDataField DataFieldName="Sprayed" Key="Sprayed" Width="60px" >
            <Header Text="Sprayed" />
        </ig:BoundDataField>
        <ig:BoundDataField DataFieldName="OpenBolls" Key="OpenBolls" Width="55px" >
            <Header Text="OpenBolls" />
        </ig:BoundDataField>
        <ig:BoundDataField DataFieldName="Recnum" Key="Recnum" Hidden="true">
            <Header Text="Sample Id" />
        </ig:BoundDataField>
        <ig:BoundDataField DataFieldName="CropId" Key="CropId" Hidden="true">
            <Header Text="Crop Id" />
        </ig:BoundDataField>
        <ig:TemplateDataField Key="colDelete" width="55px" >
            <ItemTemplate>
                <asp:ImageButton ID="btnDelete" runat="server" ImageUrl="~/Images/btnDelete.gif"
                    OnCommand="btnDelete_Select" CommandName="Select" CommandArgument='<%# Eval("Recnum") %>' />
            </ItemTemplate>
        </ig:TemplateDataField>
    </Columns>
    <Behaviors>
        <ig:Paging PagerAppearance="Bottom" PageSize="8" Enabled="true" />
        <ig:Selection CellClickAction="Row" RowSelectType="Single">
            <SelectionClientEvents RowSelectionChanged="wdgSamples_rowSelChanged" />
        </ig:Selection>
        <ig:Sorting ></ig:Sorting>
    </Behaviors>
</ig:webdatagrid>

I have a section at the bottom of the page that allows the user to enter information to be able to add a record to the grid.  For some reason, when the user saves an additional record and the page does a postback, I am getting the following error:

 DataBinding: 'Infragistics.Web.UI.GridControls.GridRecordItem' does not contain a property with the name 'Recnum'

The code highlights the line with the 'OnCommand="btnDelete_Select" CommandName="Select" CommandArgument='<% for the template button.

I have no idea why this is happening, can anyone help me with this?  This error does not happen everytime, but does occur regularly!!!