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public static void Main(params string[] args)
{
  // String dönüş tipli parametre almayan bir method:
  Func<string> findName = () => 
  {
    return "World";
  }
  
  // String tipinde bir parametre alan değer döndürmeyen (void) bir method:
  Action<string> sayHello = (name) =>

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IDataProvider<string> a = default; // Or something else...

IDataProvider<object> b = a; // ✔ There is no compile error! Everything is ok 👌.

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public interface IDataProvider<out TData>
{
    TData GetData();
}

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interface MyInterface<in T>
{
    T GetData(); // ❌This can't be used! MsBuild does'nt allow to build!

    void SetData(T data); // ✔ Everything is OK!
}

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interface MyInterface<in T>
{
}

enisn

public interface MyInterface<out T>
{
    T GetData(); // ✔That's OK

    void SetData(T data); // ❌This can't be used! MsBuild does'nt allow to build!
}

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interface MyInterface<out T>
{
}

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IEnumerable<string> a = default; // Or something else...

IEnumerable<object> b = a; //✅Everything is OK

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IDataProvider<string> a = default; // Or something else...
  
IDataProvider<object> b = a; // ❌Compile Error! Can't build.

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public class BaseClass
{
    public int Id { get; set; }
}

public class SubClass : BaseClass
{
    public string SomeData { get; set; }
}