Casting Error when reading DataGrid SortExpression

[Mo]

Hi,

I'm getting an error:
Input string was not in a correct format

This happens when I try to sort a column. It seems that the sort event
handler claims that the sort expression is not in String format, but it is.
Any suggestions would be greatly appreciated

'DATAGRID code:
<asp:DataGrid id="DataGrid1" Font-Name="Arial, Helvetica, Verdana,
sans-serif" Font-Size="10pt" Runat="server" Width="100%"
OnSortCommand=" SortSelection" AllowSorting="T rue"
AutoGenerateCol umns="false" AlternatingItem Style-BackColor="#EEE CD9"
AllowPaging="Tr ue" PageSize="10" OnPageIndexChan ged="dgGetDocs_ Paged">
<Columns>
<asp:HyperLinkC olumn DataNavigateURL Field="FullFile Path"
DataTextField=" FileName" SortExpression= "FileName" HeaderText=" Document #"
Target="_blank" HeaderStyle-BackColor="#285 193"
HeaderStyle-BorderColor="Wh ite" HeaderStyle-BorderStyle="So lid"
HeaderStyle-BorderWidth="1" HeaderStyle-ForeColor="Whit e"
HeaderStyle-Font-Size="10" HeaderStyle-Font-Bold="true"
HeaderStyle-Font-Name="Arial"></asp:HyperLinkCo lumn>
<asp:BoundColum n DataField="DocS ize" SortExpression= "'DocSize'"
HeaderText=" Size (kb)" HeaderStyle-BackColor="#285 193"
HeaderStyle-BorderColor="Wh ite" HeaderStyle-BorderStyle="So lid"
HeaderStyle-BorderWidth="1" HeaderStyle-ForeColor="Whit e"
HeaderStyle-Font-Size="10" HeaderStyle-Font-Bold="true"
HeaderStyle-Font-Name="Arial"></asp:BoundColumn >
<asp:BoundColum n DataField="DocD ate" SortExpression= "'DocDate'"
DataFormatStrin g="{0:dd-MMM-yyyy}" HeaderText=" Date Created"
HeaderStyle-BackColor="#285 193" HeaderStyle-BorderColor="Wh ite"
HeaderStyle-BorderStyle="So lid" HeaderStyle-BorderWidth="1"
HeaderStyle-ForeColor="Whit e" HeaderStyle-Font-Size="10"
HeaderStyle-Font-Bold="true"
HeaderStyle-Font-Name="Arial"></asp:BoundColumn >
<asp:BoundColum n DataField="DocT ype" SortExpression= "'DocType'"
HeaderText=" Document Type" HeaderStyle-BackColor="#285 193"
HeaderStyle-BorderColor="Wh ite" HeaderStyle-BorderStyle="So lid"
HeaderStyle-BorderWidth="1" HeaderStyle-ForeColor="Whit e"
HeaderStyle-Font-Size="10" HeaderStyle-Font-Bold="true"
HeaderStyle-Font-Name="Arial"></asp:BoundColumn >
</Columns>
</asp:DataGrid>
'Event Handler Code:
Sub SortSelection(B yVal sender As Object, ByVal e As
DataGridSortCom mandEventArgs)
BindData(e.Sort Expression)
End Sub