I have defined a class, and set

in my xml file.
I start my program and load my data in displaying it in a datagridview.
Next i load up sql management studio, connect to the database, and alter an entry in the table i have just loaded in the program.
Over in the program I make sure the change has not propergated into the datagridview.
Now i change something in the row I had altered with sql management studio.
I save my change from the datagridview to the database.

What I expected was an exception in the program, but instead I find that the change i made with sql management studio has been overwritten completely with the other data from my program.

Can anyone take a stab at where I go wrong?
PS. just say and I'll post the code I use, if you need it.