How to return value from Action

Question

In regards to the answer for this question Passing DataContext into Action    how do I return a value from action db    SimpleUsing DoUsing db   gt        do whatever with db         Should be more like   MyType myType   SimpleUsing DoUsing lt MyType gt  db   gt        do whatever with db   query buit using db returns MyType

User · Answer

You can use Func lt T  TResult gt  generic delegate   See MSDN   Func lt MyType  ReturnType gt  func    db    gt    return new MyType        Also there are useful generic delegates which considers a return value    Converter lt TInput  TOutput gt   MSDN  Predicate lt TInput gt  -  always return bool  MSDN      Method   public MyType SimpleUsing DoUsing lt MyType gt  Func lt TInput  MyType gt  myTypeFactory    Generic delegate   Func lt InputArgumentType  MyType gt  createInstance   db   gt  return new MyType      Execute   MyType myTypeInstance   SimpleUsing DoUsing                              createInstance new InputArgumentType        OR explicitly   MyType myTypeInstance   SimpleUsing DoUsing db   gt  return new MyType

User · Answer

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   gt       result   db SomeQuery      whatever returns the MyType result         do something with result

User · Answer

Use Func lt T gt  rather than Action lt T gt     Action lt T gt  acts like a void method with parameter of type T  while Func lt T gt  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 lt TParameter1  TParameter2       TReturn gt

User · Answer

Your static method should go from   public static class SimpleUsing       public static void DoUsing Action lt MyDataContext gt  action                using  MyDataContext db   new MyDataContext               action db             To   public static class SimpleUsing       public static TResult DoUsing lt TResult gt  Func lt MyDataContext  TResult gt  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

[c#] How to return value from Action()?

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