C# if Statement

Several decision-making statements are available in C# where certain logical conditions are required to flow a program continuously.

The decision-making statements included in C# are: if statement, if-else statement, switch statement, and ternary operator.

The if statement is perhaps the most basic of flow control options available to the C# programmer.

The if statement checks the given condition. If the condition evaluates to be true then the block of code/statements will execute otherwise not.

Programmers who are familiar with C, C++ or Java will immediately be comfortable using C# if statements.

1 - Syntax of C# if Statement

The C# if statement tests the condition. It is executed if condition is true.

if (condition)
    statement;

*** Note that if is in lowercase letters. Uppercase letters (If or IF) will generate an error.

If you want to execute multiple statements, you need to use a block { } like this:

if (condition) 
{
  // block of code to be executed if the condition is True
}

However, it’s a good practice to always use a block with the if statement even though it has a simple statement.

Note: If the curly brackets { } are not used with if statements then the statement just next to it is only considered associated with the if statement. 

Example: 

if (condition)
   statement 1;
statement 2;

In this example, only statement 1 is considered to be associated with the if statement.

2 - C# Conditions and If Statements

C# supports the usual logical conditions from mathematics:

• Less than: a < b
• Less than or equal to: a <= b
• Greater than: a > b
• Greater than or equal to: a >= b
• Equal to: a == b
• Not Equal to: a != b

You can use these conditions to perform different actions for different decisions.

3 - C# If Statement Flow Chart Diagram

The following flowchart illustrates how the C# if statement works:

4 - C# if statement examples

Let’s take some examples of using the if statement.

01. Example 1

if (5 < 2 * 3) {
    Console.WriteLine ("true"); // true 
}

The statement can be a code block:

if (5 < 6) {
 Console.WriteLine ("true");
 Console.WriteLine ("Let's move on!"); 
} 

02. Example 2

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace HelloWorld
{
    class Program
    {
        static void Main(string[] args)
        {
            /* local variable definition */
            int a = 10;
            /* check the boolean condition using if statement */
            if (a < 20)
            {
                /* if condition is true then print the following */
                Console.WriteLine("a is less than 20");
            }
            Console.WriteLine("value of a is : {0}", a);
            Console.ReadLine();
        }
    }
}

Output:

When the above code is compiled and executed, it produces the following result: