How to return value from Action()?
You can use Func<T, TResult>
generic delegate. (See MSDN)
Func<MyType, ReturnType> func = (db) => { return new MyType(); }
Also there are useful generic delegates which considers a return value:
Converter<TInput, TOutput>
(MSDN)Predicate<TInput>
- always return bool (MSDN)
Method:
public MyType SimpleUsing.DoUsing<MyType>(Func<TInput, MyType> myTypeFactory)
Generic delegate:
Func<InputArgumentType, MyType> createInstance = db => return new MyType();
Execute:
MyType myTypeInstance = SimpleUsing.DoUsing(
createInstance(new InputArgumentType()));
OR explicitly:
MyType myTypeInstance = SimpleUsing.DoUsing(db => return new MyType());
You can also take advantage of the fact that a lambda or anonymous method can close over variables in its enclosing scope.
MyType result;
SimpleUsing.DoUsing(db =>
{
result = db.SomeQuery(); //whatever returns the MyType result
});
//do something with result
Your static method should go from:
public static class SimpleUsing
{
public static void DoUsing(Action<MyDataContext> action)
{
using (MyDataContext db = new MyDataContext())
action(db);
}
}
To:
public static class SimpleUsing
{
public static TResult DoUsing<TResult>(Func<MyDataContext, TResult> action)
{
using (MyDataContext db = new MyDataContext())
return action(db);
}
}
This answer grew out of comments so I could provide code. For a complete elaboration, please see @sll's answer below.
Use Func<T>
rather than Action<T>
.
Action<T>
acts like a void method with parameter of type T, while Func<T>
works like a function with no parameters and which returns an object of type T.
If you wish to give parameters to your function, use Func<TParameter1, TParameter2, ..., TReturn>
.