I have one of your tutorials titled “Using TemplateFields in the GridView Control” with all 4 features working fine with all valid HireDate Values. If a HireDate is deleted or not available the program fails.

To run the Application with valid dates, I have made a URL available on the Internet , that works fine rayheadly.com/ I have placed a second URL rayheadly.com/ to modify individual records.

When I removed the HireDate from any record an error occurs. If I ran this program again and tried to re-enter a corrected DateTime it also is rejected.

The two URL’s both the On-Line and Client are identical. The programs work correctly on the Client.

I would welcome a solution to this problem. It is a routine, I am particularly anxious to understand the use of CodeBehind when a record or field is not available.

Rgds Ray

Rgds Ray

I learnt a lot last year going through your Data Access tutorials here. It meant I could have my first .NET project with a proper DAL, BLL and Presentation Layer and I was very happy with the results. But I am revisiting it now having read more around the subject of layering applications and now I am confused about something.

You have code in the Presentation Layer that access type declarations from the DAL. One example is on this page:

protected string DisplayDaysOnJob(Northwind.EmployeesRow employee)

{

// Make sure HiredDate is not null... if so, return "Unknown"

if (employee.IsHireDateNull())

return "Unknown";

else

{

// Returns the number of days between the current

// date/time and hiredDate

TimeSpan ts = DateTime.Now.Subtract(employee.HireDate);

return ts.Days.ToString("#,##0");

}

}

The Northwind class is defined in the DAL, not the BLL. So why is it OK for a code-behind in the Presentation Layer to access the DAL for the EmployeesRow type? Is it because it doesn't call any database code, but just uses those classes just to store strongly typed data in the Presentation Layer? Or does this technically break the DAL/BLL/Presentation layers but you don't think it is an issue? If so, why not?

I was considering ways to avoid this using a separate Model assembly that would be inherited by both the BLL and the DAL and passing everything around as collections of objects rather than data tables, but I think this would open a large can of worms. So I'm hoping this is my misunderstanding of the separation that the layers should have.

Thanks.

Markup:

<asp:TemplateField HeaderText="Days On The Job">

<ItemTemplate>

<%# DisplayDaysOnJob((DateTime?)Eval("HireDate"))%>

</ItemTemplate>

</asp:TemplateField>

Code:

protected string DisplayDaysOnJob(DateTime? hireDate)

{

// Make sure HiredDate is not null... if so, return "Unknown"

if (hireDate == null || !hireDate.HasValue)

return "Unknown";

else

{

// Returns the number of days between the current

// date/time and HireDate

TimeSpan ts = DateTime.Now.Subtract(hireDate.Value);

return ts.Days.ToString("#,##0");

}

}

<asp:Calendar ID="Calendar1" runat="server" Enabled="False"

SelectedDate='<%# Eval("HireDate") is System.DateTime?(System.DateTime)Eval("HireDate"):System.DateTime.Today %>'

VisibleDate='<%# Eval("HireDate") is System.DateTime?(System.DateTime)Eval("HireDate"):System.DateTime.Today %>'

Visible='<%# Eval("HireDate") is System.DateTime %>'>

</asp:Calendar>

Hi,I had the same problem.

I solved it by clicking _Refresh Schema_ in the left-down corner of the EditDataBindings window.