c# - Detect if deleting DataGrid row is valid to delete -

i use ef code-first datagrid itemssourse, how can detect on previewkeyup event if items user want delete valid deleted or not.

for example, if user delete 'customer', , 'order' contains customerid illegal. there way know if identifier of item user want delete being used foreign key in table? ef has information on it?

something that:

private void datagridex_previewkeyup(object sender, system.windows.input.keyeventargs e) {     if (e.key == key.delete) {         if (e.originalsource datagridcell) {             datagrid datagrid = sender;             if (!isvalidtodelete(datagrid.selectedcells)) {                 e.handled = true;                 msgbox("not valid delete !");             }         }     } } 

it sounds there's selected row in customer grid, , you're evaluating whether or not delete selected customer.

and customer , order both in ef model.

so customer, find id, , write query checks order table in ef model orders customer id. here's idea, semantically -- actual code bit different, no doubt.

var selcustomerid = (datagrid.selectedrow customer).customerid; var customerhasorder = myefmodel.order.any(ordr => ordr.customerid == selcustomerid); 

think of any call being loop that'll call lambda each row in myefmodel.order, , return true first time lambda returns true.

ordr => ordr.customerid == selcustomerid 

in reality, of course, since you're doing linq ef, it's generating sql query.