Hi an example of business logic would look like this:
public partial class NorthwindDataContext : System.Data.Linq.DataContext
{
partial void InsertCustomer(Customer instance)
{
var NWDC = new NorthwindDataContext();
if (NWDC.Customers.SingleOrDefault(c => c.CustomerID == instance.CustomerID) != null)
{
throw new ValidationException("Duplicate CustoemrID is not allowed");
}
else
{
// finally send this to the DB
this.ExecuteDynamicInsert(instance);
}
}
}Here I have implemented the partial method InsertCustomer for the NorthwindDataContext so what I'm doing is checking that there is not already a customer with the same CustomerID.
You could also look at Scot Guthries Linq to SQL series
Part 6: Retrieving Data Using Stored Procedures
Part 7: Updating our Database using Stored Procedures
if you want to implement some of your business login in T-SQL sprocs.
Hope this helps 
Steve

Always seeking an elegant solution.
[Oh! If olny I colud tpye!]
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