constraints

I need to create a custom constraint annotation which can access the value of another field of my bean. I'll use this annotation to validate the field because it depends on the value of the other but the way I define it the compiler says "The value for annotation attribute" of my field "must be a constant expression". I've defined it in this way: @Target(ElementType.FIELD) @Retention(RetentionPolicy.RUNTIME) @Constraint(validatedBy=EqualsFieldValidator.class) @Documented public @interface EqualsField { public String field(); String message() default "{com.myCom.annotations.EqualsField.message}

I'm trying to write an extension method on IEnumerable that will only apply to value types and strings. public static string MyMethod<T>(this IEnumerable<T> source) where T : struct, string However 'string' is not a valid constraint as it is a sealed class. Is there any way to do this? Edit: What I'm actually trying to do is prepare a list of values for an "IN" clause in a dynamically constructed SQL. I have lots of instances of code such as the following that I want to clean up: sb.AppendLine(string.Format("AND value IN ({0})", string.Join(",", Values.Select(x => x.ToSQL()).ToArray())));

I have the code to fire a trigger only on an update of a single specific column. The trigger is used to fire a function that will raise a postgres "notify" event, which I am listening for and will need to test and validate the newly input details. There are many values on the account_details table which could be change which do not require an account validate, so a trigger on AFTER UPDATE only (without a when) is no good. CREATE TRIGGER trigger_update_account_details AFTER UPDATE ON account_details FOR EACH ROW WHEN (OLD.email IS DISTINCT FROM NEW.email) EXECUTE PROCEDURE notify_insert_account

class Sample<T> : IDisposable // case A { public void Dispose() { throw new NotImplementedException(); } } class SampleB<T> where T : IDisposable // case B { } class SampleC<T> : IDisposable, T : IDisposable // case C { public void Dispose() { throw new NotImplementedException(); } } Case C is the combination of case A and case B. Is that possible? How to make case C right? First the implemented interfaces, then the generic type constraints separated by where : class SampleC<T> : IDisposable where T : IDisposable // case C { // ↑ public void Dispose() { throw new NotImplementedException(); } }