C# Expressions, Statements and Blocks (With Examples)

Expressions, statements and blocks are the building block of a C# program. We have been using them since our first "Hello World" program.

C# Expressions

An expression in C# is a combination of operands (variables, literals, method calls) and operators that can be evaluated to a single value. To be precise, an expression must have at least one operand but may not have any operator.

Let's look at the example below:

double temperature;
temperature = 42.05;

Here, 42.05 is an expression. Also, temperature = 42.05 is an expression too.

int a, b, c, sum;
sum = a + b + c;

Here, a + b + c is an expression.

if (age>=18 && age<58)
	Console.WriteLine("Eligible to work");

Here, (age>=18 && age<58) is an expression that returns a boolean value. "Eligible to work" is also an expression.

C# Statements

A statement is a basic unit of execution of a program. A program consists of multiple statements.

For example:

int age = 21;
Int marks = 90;

In the above example, both lines above are statements.

There are different types of statements in C#. In this tutorial, we’ll mainly focus on two of them:

1. Declaration Statement
2. Expression Statement

Declaration Statement

Declaration statements are used to declare and initialize variables.

For example:

char ch;
int maxValue = 55;

Both char ch; and int maxValue = 55; are declaration statements.

Expression Statement

An expression followed by a semicolon is called an expression statement.

For example:

/* Assignment */
area = 3.14 * radius * radius;
/* Method call is an expression*/

System.Console.WriteLine("Hello");

Here, 3.14 * radius * radius  is an expression and area = 3.14 * radius * radius; is an expression statement.

Likewise, System.Console.WriteLine("Hello"); is both an expression and a statement.

Beside declaration and expression statement, there are:

• Selection Statements (if...else, switch)
• Iteration Statements (do, while, for, foreach)
• Jump Statements (break, continue, goto, return, yield)
• Exception Handling Statements (throw, try-catch, try-finally, try-catch-finally)

These statements will be discussed in later tutorials.

If you want to learn more about statements, visit C# Statements ( C# reference)

C# Blocks

A block is a combination of zero or more statements that is enclosed inside curly brackets { }.

For example:

Example 1: C# Blocks with statements

using System;

namespace Blocks
{
	class BlockExample
	{
		public static void Main(string[] args)
		{
			double temperature = 42.05;
			if (temperature > 32)
			{	// Start of block
				Console.WriteLine("Current temperature = {0}", temperature);
				Console.WriteLine("It's hot");
			}	// End of block
		}
	}
}

When we run the program, the output will be:

Current temperature = 42.05
It's hot

Here, the two statements inside { }:

Console.WriteLine("Current temperature = {0}", temperature);

and

Console.WriteLine("It's hot");

forms a block.

Example 2: C# Blocks without statements

A block may not have any statements within it as shown in the below example.

using System;

namespace Blocks
{
	class BlockExample
	{
		public static void Main(string[] args)
		{
			double temperature = 42.05;
			if (temperature > 32)
			{	// Start of block
				// No statements
			}	// End of block
		}
	}
}

Here, the curly braces { } after if(temperature > 32) contains only comments and no statements.