[C#] Dictionary Example

using System;
using System.Collections.Generic;

class Program
{
    static void Main()
    {
        Dictionary dictionary = new Dictionary();

        dictionary.Add("cat", 2);
        dictionary.Add("dog", 1);
        dictionary.Add("llama", 0);
        dictionary.Add("iguana", -1);
    }
}

using System.Collections.Generic;

class Program
{
    static void Main()
    {
        var values = new Dictionary();
        values.Add("A", "uppercase letter A");
        values.Add("c", "lowercase letter C");

        // Use inline "out string" with TryGetValue.
        if (values.TryGetValue("c", out string description))
        {
            System.Console.WriteLine(description);
        }
    }
}

using System;
using System.Collections.Generic;

class Program
{
    static void Main()
    {
        // Example Dictionary again.
        Dictionary d = new Dictionary()
        {
            {"cat", 2},
            {"dog", 1},
            {"llama", 0},
            {"iguana", -1}
        };
        // Loop over pairs with foreach.
        foreach (KeyValuePair pair in d)
        {
            Console.WriteLine("{0}, {1}", pair.Key, pair.Value);
        }
        // Use var keyword to enumerate dictionary.
        foreach (var pair in d)
        {
            Console.WriteLine("{0}, {1}", pair.Key, pair.Value);
        }
    }
}

using System;
using System.Collections.Generic;

class Program
{
    static void Main()
    {
        Dictionary d = new Dictionary()
        {
            {"cat", 2},
            {"dog", 1},
            {"llama", 0},
            {"iguana", -1}
        };
        // Store keys in a List.
        List list = new List(d.Keys);
        // Loop through list.
        foreach (string k in list)
        {
            Console.WriteLine("{0}, {1}", k, d[k]);
        }
    }
}

using System;
using System.Collections.Generic;
using System.Diagnostics;

class Program
{
    static void Main()
    {
        var test = new Dictionary();
        test["bird"] = 10;
        test["frog"] = 20;
        test["cat"] = 60;
        int sum = 0;
        const int _max = 1000000;

        // Version 1: use foreach loop directly on Dictionary.
        var s1 = Stopwatch.StartNew();
        for (int i = 0; i < _max; i++)
        {
            foreach (var pair in test)
            {
                sum += pair.Value;
            }
        }
        s1.Stop();

        // Version 2: use foreach loop on Keys, then access values.
        var s2 = Stopwatch.StartNew();
        for (int i = 0; i < _max; i++)
        {
            foreach (var key in test.Keys)
            {
                sum += test[key];
            }
        }
        s2.Stop();
        Console.WriteLine(s1.Elapsed.TotalMilliseconds);
        Console.WriteLine(s2.Elapsed.TotalMilliseconds);
    }
}

using System;
using System.Collections.Generic;

class Program
{
    static void Main()
    {
        // Use a Dictionary with an int key.
        Dictionary dict = new Dictionary();
        dict.Add(100, "Bill");
        dict.Add(200, "Steve");
        // We can look up the int in the Dictionary.
        if (dict.ContainsKey(200))
        {
            Console.WriteLine(true);
        }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;

class Program
{
    static void Main()
    {
        string[] arr = new string[]
        {
            "One",
            "Two"
        };
        var dict = arr.ToDictionary(item => item, item => true);
        foreach (var pair in dict)
        {
            Console.WriteLine("{0}, {1}",
                pair.Key,
                pair.Value);
        }
    }
}

using System;
using System.Collections.Generic;

class Program
{
    static void Main()
    {
        Dictionary d = new Dictionary();
        d.Add("cat", 1);
        d.Add("dog", 2);
        if (d.ContainsValue(1))
        {
            Console.WriteLine(true); // True.
        }
    }
}

using System;
using System.Collections.Generic;

class Program
{
    static void Main()
    {
        Dictionary dictionary = new Dictionary();

        // We can assign with the indexer.
        dictionary[1] = 2;
        dictionary[2] = 1;
        dictionary[1] = 3; // Reassign.

        // Read with the indexer.
        // ... An exception occurs if no element exists.
        Console.WriteLine(dictionary[1]);
        Console.WriteLine(dictionary[2]);
    }
}

using System;
using System.Collections.Generic;

class Program
{
    static void Main()
    {
        Dictionary d = new Dictionary();
        d.Add("cat", 1);
        d.Add("dog", 2);

        d.Remove("cat"); // Removes cat.
        d.Remove("nothing"); // Doesn't remove anything.
    }
}

using System;
using System.Collections.Generic;

class Program
{
    static void Main()
    {
        Example e = new Example();
        Console.WriteLine(e.GetValue());
    }
}

class Example
{
    Dictionary _d = new Dictionary()
    {
        {1, 1},
        {2, 3},
        {3, 5},
        {6, 10}
    };
    public int GetValue()
    {
        return _d[2]; // Example only.
    }
}