using System;

using System.Collections.Generic;

​

public class Program

{

    public static void Main()

    {

        #region Assignment compatibility

        string str = "Test";

        //An object of a more derived type is assigned to an object of a less derived type.

        object obj1 = str;

        #endregion Assignment compatibility

        #region Covariance (Array)

        object[] array = new String[10];

        //But this operation is not type safe

        // The following statement produces a run-time exception.  

        // array[0] = 10; 

        #endregion Covariance (Array)

        #region Covariance (Generic Interface)

        IEnumerable<string> strings = new List<string>();

        // An object that is instantiated with a more derived type argument 

        // is assigned to an object instantiated with a less derived type argument.

        // So, assignment compatibility is preserved.

        IEnumerable<object> objects = strings;

        #endregion Covariance (Generic Interface)

        #region Covariance (In Delegates)

        // A delegate specifies a return type as object, 

        // but you can assign a method that returns as string.

        Func<object> del = GetString;

        #endregion Covariance (In Delegates)

        #region Contravariance (In Delegates)       

        // An object that is instantiated with a less derived type argument

        // is assigned to an object instantiated with a more derived type argument.

        // So, assignment compatibility is reversed.

        Action<string> del2 = SetObject;

        #endregion Contravariance (In Delegates)

    }

​

    static void SetObject(object o) { }

    static string GetString() { return ""; }

}