using System;

using System.Collections.Generic;

using System.Linq;

​

public class Program

{

    public static void Main()

    {

        Dictionary<int, ExampleObject> list = new Dictionary<int, ExampleObject>

        {

            {1, new ExampleObject(1) }, 

            {2, new ExampleObject(2) }, 

            {3, new ExampleObject(3) }, 

            {4, new ExampleObject(4) }, 

            {5, new ExampleObject(5) }, 

            {6, new ExampleObject(6) }, 

            {7, new ExampleObject(7) }

        };

        Console.WriteLine("Using Direct");

        foreach(KeyValuePair<int, ExampleObject> el in list)

        {

            try

            {

                Console.Write("\nBefore "+el.Value.Value.ToString());

                el.Value.Value += 1;

                Console.Write(" - After "+el.Value.Value.ToString());

                Console.WriteLine("\nCould modify in foreach");

            }

            catch

            {

                Console.WriteLine("Couldn't modify "+el.ToString());    

            }

        }

        list = new Dictionary<int, ExampleObject>

        {

            {1, new ExampleObject(1) }, 

            {2, new ExampleObject(2) }, 

            {3, new ExampleObject(3) }, 

            {4, new ExampleObject(4) }, 

            {5, new ExampleObject(5) }, 

            {6, new ExampleObject(6) }, 

            {7, new ExampleObject(7) }

        };

        Console.WriteLine("\nUsing Method");

        foreach(KeyValuePair<int, ExampleObject> el in list)

        {

            try

            {

                Console.Write("\nBefore "+el.Value.Value.ToString());

                el.Value.Add(1);

                Console.Write(" - After "+el.Value.Value.ToString());

                Console.WriteLine("\nCould modify in foreach");

            }

            catch

            {

                Console.WriteLine("Couldn't modify "+el.ToString());    

            }

        }

        list = new Dictionary<int, ExampleObject>

        {

            {1, new ExampleObject(1) }, 

            {2, new ExampleObject(2) }, 

            {3, new ExampleObject(3) }, 

            {4, new ExampleObject(4) }, 

            {5, new ExampleObject(5) }, 

            {6, new ExampleObject(6) }, 

            {7, new ExampleObject(7) }

        };

        Console.WriteLine("\nUsing Linq Direct");

        list.ToList().ForEach(el =>

        {

            try

            {

                Console.Write("\nBefore "+el.Value.Value.ToString());

                el.Value.Value += 1;

                Console.Write(" - After "+el.Value.Value.ToString());

                Console.WriteLine("\nCould modify in foreach");

            }

            catch

            {

                Console.WriteLine("Couldn't modify "+el.ToString());    

            }

        });

        list = new Dictionary<int, ExampleObject>

        {

            {1, new ExampleObject(1) }, 

            {2, new ExampleObject(2) }, 

            {3, new ExampleObject(3) }, 

            {4, new ExampleObject(4) }, 

            {5, new ExampleObject(5) }, 

            {6, new ExampleObject(6) }, 

            {7, new ExampleObject(7) }

        };

        Console.WriteLine("\nUsing Linq Method");

        list.ToList().ForEach(el =>

        {

            try

            {

                Console.Write("\nBefore "+el.Value.Value.ToString());

                el.Value.Add(1);

                Console.Write(" - After "+el.Value.Value.ToString());

                Console.WriteLine("\nCould modify in foreach");

            }

            catch

            {

                Console.WriteLine("Couldn't modify "+el.ToString());    

            }

        });

    }

}

​

public class ExampleObject

{

    public int Value;

    public ExampleObject(int val)

    {

        Value = val;    

    }

    public void Add(int addition)

    {

        Value += addition;  

    }

}