Difference between == and .Equals method in c#

For Value Type:
== and .Equals() method usually compare two objects by value.

For Example:

int x = 20;

int y = 20;

Console.WriteLine( x == y);

Console.WriteLine(x.Equals(y));

Output:

True

True

For Reference Type:

== performs an identity comparison,
i.e. it will only return true
if both references point to the same object.
While Equals() method is expected to
perform a value comparison, i.e. it will
return true if the references point
to objects that are equivalent.

For Example:
StringBuilder s1 = new StringBuilder(“Yes”);

StringBuilder s2 = new StringBuilder(“Yes”);

Console.WriteLine(s1 == s2);

Console.WriteLine(s1.Equals(s2));

Output:

False

True

In above example, s1 and s2 are different objects hence “==” returns
false, but they are equivalent hence “Equals()”
method returns true. Remember there is an exception of this rule,
i.e. when you use “==” operator with string class it
compares value rather than identity.

When to use “==” operator and when to use “.Equals()” method?

For value comparison, with Value Type use “==” operator
and use “Equals()” method while performing value comparison
with Reference Type.

Return Multiple values from a function in C#

In C#, There are 4 ways to return multiple values from a C# function.

• Using KeyValue pair
• Using ref/out parameters
• Using Struct or Class
• Using Tuple

1. Using KeyValue pair:

class Program

    {

        static void Main(string[] args)

        {

            int int1 = 15;

            int int2 = 25;

            var result = Add_Multiply(int1, int2);

            Console.WriteLine(result.Key);

            Console.WriteLine(result.Value);

        }

        private static KeyValuePair<int, int> Add_Multiply(int int1, int int2)

        {

            var KeyValuePair = new KeyValuePair<int, int>(int1 + int2, int1 * int2);

            return KeyValuePair;

        }

    }

Output:

40
375

2.a. Using Ref Parameter:

 class Program

    {

        static void Main(string[] args)

        {

            int int1 = 15;

            int int2 = 25;

            int add = 0;

            int multiply = 0;

            Add_Multiply(int1, int2, ref add, ref multiply);

            Console.WriteLine(add);

            Console.WriteLine(multiply);

        }

        private static void Add_Multiply(int int1, int int2, ref int add, ref int multiply)

        {

            add = int1 + int2;

            multiply = int1 * int2;

        }

    }

40
375

2.b. Using Out Parameter:

class Program

    {

        static void Main(string[] args)

        {

            int int1 = 15;

            int int2 = 25;

            int add = 0;

            int multiply = 0;

            Add_Multiply(int1, int2, out add, out multiply);

            Console.WriteLine(add);

            Console.WriteLine(multiply);

        }

        private static void Add_Multiply(int int1, int int2, out int add, out int multiply)

        {

            add = int1 + int2;

            multiply = int1 * int2;

        }

    }

Output:

40
375

3.a. Using Struct:

class Program

    {

        struct Result

        {

            public int add;

            public int multiply;

        }

        static void Main(string[] args)

        {

            int int1 = 53;

            int int2 = 17;

            var result = Add_Multiply(int1, int2);

            Console.WriteLine(result.add);

            Console.WriteLine(result.multiply);

        }

        private static Result Add_Multiply(int int1, int int2)

        {

            var result = new Result

            {

                add = int1 + int2,

                multiply = int1 * int2

            };

            return result;

        }

    }

Output:

70
901

3.b. Using Class:

struct Result

        {

            public int add;

            public int multiply;

        }

        static void Main(string[] args)

        {

            int int1 = 13;

            int int2 = 27;

            var result = Add_Multiply(int1, int2);

            Console.WriteLine(result.add);

            Console.WriteLine(result.multiply);

        }

        private static Result Add_Multiply(int int1, int int2)

        {

            var result = new Result

            {

                add = int1 + int2,

                multiply = int1 * int2

            };

            return result;

        }

    }

Output:

40
351

4. Using Tuple:

class Program

{

        static void Main(string[] args)

        {

            int int1 = 25;

            int int2 = 28;

            var result = Add_Multiply(int1, int2);

            Console.WriteLine(result.Item1);

            Console.WriteLine(result.Item2);

        }

        private static Tuple<int, int> Add_Multiply(int int1, int int2)

        {

            var tuple = new Tuple<int, int>(int1 + int2, int1 * int2);

            return tuple;

        }

}

Remove Duplicate characters from String in C#

class Program

    {

        static void Main()

        {

            string value1 = RemoveDuplicateChars("Csharpstar");

            string value2 = RemoveDuplicateChars("Google");

            string value3 = RemoveDuplicateChars("Yahoo");

            string value4 = RemoveDuplicateChars("CNN");

            string value5 = RemoveDuplicateChars("Line1\nLine2\nLine3");

 

            Console.WriteLine(value1);

            Console.WriteLine(value2);

            Console.WriteLine(value3);

            Console.WriteLine(value4);

            Console.WriteLine(value5);

        }

 

        static string RemoveDuplicateChars(string key)

        {

            // --- Removes duplicate chars using string concats. ---

            // Store encountered letters in this string.

            string table = "";

 

            // Store the result in this string.

            string result = "";

 

            // Loop over each character.

            foreach (char value in key)

            {

                // See if character is in the table.

                if (table.IndexOf(value) == -1)

                {

                    // Append to the table and the result.

                    table += value;

                    result += value;

                }

            }

            return result;

        }

    }

Input: Google
Output: Gogle