Question

Sorry guys! i am so into the code! that i forgot to put the compiler errors.

Here is a new version of the code simplified!

And this are the errors:

Error 1 The best overloaded method match for ‘IWeird.DataBase.ModifyData(ref IWeird.IDataTable)’ has some invalid arguments
Error 2 Argument ‘1’: cannot convert from ‘ref IWeird.Periods’ to ‘ref IWeird.IDataTable’

The problem:
I can’t pass by reference an interface with a struct in it,
what am I doing wrong?

Here is the new example code:

class PeriodsProcessor
    {
        public PeriodsProcessor()
        {
            Periods Data = new Periods();
            DataBase DB = new DataBase();

            Console.WriteLine(Data.Value);
            DB.ModifyData(ref Data);
            Console.WriteLine(Data.Value);

            Console.ReadLine();
        }
    }


    public interface IDataTable
    {
        string Value { get; set; }
    }

    public struct Periods : IDataTable
    {
        public string Value { get; set; }
    }

    public class DataBase
    {
        public void ModifyData(ref IDataTable data) 
        {
            data.Value = "CHANGE";
        }
    }

    class Program
    {
        static void Main(string[] args)
        {
            PeriodsProcessor PeriodsProcessor = new PeriodsProcessor();
        }
    }

Answer 1

The problem is in DB.ModifyData<Period>(Data); method call. Your Data field is a struct, structs are passed to any methods by value which means that each time you call a method copy of the struct is created and is passed to the method. So actually your ModifyData method is modifying a copy of the Periods structure that is thrown away just after the method call.