CSharp – if Statement

With if statement you can set up conditional blocks of code.

if – else if – else

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using System;
 
namespace ConsoleApplication1
{
    class Program
    {
        static void Main()
        {
            Console.Write("Enter a character: ");
            char ch = (char)Console.Read();
 
            if (Char.IsUpper(ch))
            {
                Console.WriteLine("The character is an uppercase letter.");
            }
            else if (Char.IsLower(ch))
            {
                Console.WriteLine("The character is a lowercase letter.");
            }
            else if (Char.IsDigit(ch))
            {
                Console.WriteLine("The character is a number.");
            }
            else
            {
                Console.WriteLine("The character is not alphanumeric.");
            }
        } // End Main()
    }
}

if – nested

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using System;
 
namespace ConsoleApplication1
{
    class Program
    {
        static void Main()
        {
            Console.Write("Enter a character: ");
            char c = (char)Console.Read();
            if (Char.IsLetter(c))
            {
                if (Char.IsLower(c))
                {
                    Console.WriteLine("The character is lowercase.");
                }
                else
                {
                    Console.WriteLine("The character is uppercase.");
                }
            }
            else
            {
                Console.WriteLine("The character isn't an alphabetic character.");
            }
        } // End Main()
    }
}

if – boolean

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using System;
 
namespace ConsoleApplication1
{
    class Program
    {
        static void Main()
        {
            // Change the values of these variables to test the results.
            bool Condition1 = true;
            bool Condition2 = true;
            bool Condition3 = true;
            bool Condition4 = true;
 
            if (Condition1)
            {
                // Condition1 is true.
            }
            else if (Condition2)
            {
                // Condition1 is false and Condition2 is true.
            }
            else if (Condition3)
            {
                if (Condition4)
                {
                    // Condition1 and Condition2 are false. Condition3 and Condition4 are true.
                }
                else
                {
                    // Condition1, Condition2, and Condition4 are false. Condition3 is true.
                }
            }
            else
            {
                // Condition1, Condition2, and Condition3 are false.
            }
        } // End Main()
    }
}

if – AND NOT

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using System;
 
namespace ConsoleApplication1
{
    class Program
    {
        static void Main()
        {
            // NOT
            bool result = true;
            if (!result)
            {
                Console.WriteLine("The condition is true (result is false).");
            }
            else
            {
                Console.WriteLine("The condition is false (result is true).");
            }
 
            // Short-circuit AND
            int m = 9;
            int n = 7;
            int p = 5;
            if (m >= n && m >= p)
            {
                Console.WriteLine("Nothing is larger than m.");
            }
 
            // AND and NOT
            if (m >= n && !(p > m))
            {
                Console.WriteLine("Nothing is larger than m.");
            }
 
            // Short-circuit OR
            if (m > n || m > p)
            {
                Console.WriteLine("m isn't the smallest.");
            }
 
            // NOT and OR
            m = 4;
            if (!(m >= n || m >= p))
            {
                Console.WriteLine("Now m is the smallest.");
            }
            // Output:
            // The condition is false (result is true).
            // Nothing is larger than m.
            // Nothing is larger than m.
            // m isn't the smallest.
            // Now m is the smallest.
        } // End Main()
    }
}

My Website: http://www.lucedigitale.com

References:
http://msdn.microsoft.com/it-it/library/5011f09h.aspx
http://csharp.net-tutorials.com/basics/if-statement/