SQL Server

Code On Time web applications automatically handle storage of binary large objects (BLOB). For example, the Northwind sample database contains pictures of each record in the Categories table. The web app displays the pictures in the grid and form views. Clicking on the thumbnail will download the picture.

Open the edit form for a category and edit the record. The control under the Picture thumbnail allows replacing or clearing the blob stored in the field.

Any type of file may be uploaded to the field. However, the file name and type is not stored by the database. When the user tries to download the file again, the user will receive a message similar to the one below.

The generic file name is “CategoriesPicture_1” and the content type is “.octet-stream”.

In order to preserve the file name and type, utility fields will be added to the Categories table.

Adding Utility Fields

Start SQL Server Management Studio. In the Object Explorer, right-click on Databases / Northwind / Categories and press Design.

Add the following columns:

Please note that these columns are case-sensitive. If the name of your field is “XXX”, the application framework will attempt to locate utility fields “XXXFileName”, “XXXContentType”, and “XXXLength”.

Save the changes to the table.

Refreshing the Project

Start the web application generator. Click on the project name and press Refresh. Select Categories controller and continue to refresh the project.

Viewing the Results

Continue to regenerate the web app. When complete, navigate to the Categories page. Select a record, and upload any non-image file.

Note that the three utility fields have automatically been updated. Click on the thumbnail to download the file. Note that the file name and type have been correctly added.

SQL business rules allow server-side code to be executed in response to certain conditions. In addition to executing anonymous SQL code blocks, business rules can also be used in order to trigger a stored procedure.

Let’s create a stored procedure in the Northwind database that will calculate the average value of Freight for a specified customer. Then, a business rule will be added that will be triggered before every Update and Insert command in the Orders controller, and will use the stored procedure to verify that the Freight does not exceed the average freight. If it does, a message will be displayed and the command will be canceled.

Creating a Stored Procedure

Start SQL Server Management Studio. In the Object Explorer, right-click on Databases / Northwind node, and press New Query.

Insert the following query:

create procedure sp_ValidateFreight
    -- inputted customer
    @CustomerID nvarchar(5),
    -- returned average freight
    @AverageFreight money output
as
begin
   select @AverageFreight = AVG(Freight) 
   from Orders
   where CustomerID = @CustomerID
end
go

On the toolbar, press Execute to create the stored procedure.

Adding the Business Rule

Start the Project Designer. In the Project Explorer, switch to the Controllers tab. Right-click on Orders / Business Rules node, and press New Business Rule.

Assign the following values:

declare @AvgFreightOfOrders money
-- execute stored procedure
exec sp_ValidateFreight @CustomerID,
    @AverageFreight = @AvgFreightOfOrders output
-- check the freight
if @AvgFreightOfOrders is not null 
    and @AvgFreightOfOrders < @Freight 
begin
    -- prevent actual Update or Insert from happening
    set @BusinessRules_PreventDefault = 1 
    -- show an alert next to the Freight field
    set @Result_Focus = 'Freight,The freight exceeds the average' 
    + ' of $' + CONVERT(varchar(12), @AvgFreightOfOrders, 1) 
    + ' of previous orders.'
end

Press OK to save the business rule.

Viewing the Results

On the toolbar, press Browse. When generation is complete, navigate to the Customers page, select a customer, and create a new order. Enter a very high value for Freight, and save the record. The save will be canceled and a message will be displayed next to Freight.

Enter a value below the displayed average and press OK. The order will be saved.