Operator Precedence in C#

If you want to learn more about Operator Precedence

Operator Precedence Table

In C#, operators are grouped into levels of precedence. Below is a table that shows some of the most common operators organized by their precedence, from highest to lowest.

How Operator Precedence Works

Evaluating Expressions

Operator precedence determines the order of evaluation in complex expressions. For example, suppose we have the following expression:

int result = 3 + 4 * 2; // equivalent to 3 + (4 * 2) = 11

In this expression, the multiplication (*) has a higher precedence than the addition (+). Therefore, 4 * 2 is evaluated first, resulting in 8, and then 3 is added, resulting in 11.

Using Parentheses

To change the order of evaluation, we can use our faithful friends, parentheses. Parentheses have the highest precedence and force the evaluation of the expression they contain first.

int result = (3 + 4) * 2;

Here, 3 + 4 is evaluated first due to the parentheses, resulting in 7, and then multiplied by 2, resulting in 14.

Associativity

When operators have the same precedence, associativity determines the order of evaluation. Most operators in C# have left-to-right associativity, meaning they are evaluated from left to right.

However, some operators, like assignment operators, have right-to-left associativity.

int a = 1;
int b = 2;
int c = 3;
int result = a + b - c;

In this example, both + and - have the same precedence and left-to-right associativity. Therefore, a + b is evaluated first, resulting in 3, and then 3 - c is evaluated, resulting in 0.

Complex Example

Let’s consider a more complex expression to illustrate how precedence and associativity combine:

int result = 5 + 2 * 3 - 4 / 2 + (1 + 3);

We evaluate step by step according to precedence and associativity:

1. Evaluate the expression in parentheses: (1 + 3), resulting in 4.
2. Evaluate the multiplication: 2 * 3, resulting in 6.
3. Evaluate the division: 4 / 2, resulting in 2.
4. Evaluate the remaining operations from left to right:
   • 5 + 6 results in 11.
   • 11 - 2 results in 9.
   • 9 + 4 results in 13.

Therefore, the final result of the expression is 13.

Best Practices Tips

Although operator precedence allows for omitting parentheses in many situations, it’s a good practice to use parentheses to improve code clarity. This not only makes the code easier to understand but also reduces the likelihood of errors.

int result = (5 + 2) * (3 - 1);

Understanding Compound Operators

Compound operators, like += and -=, combine assignment with another operation. These operators have lower precedence, which can affect the results of expressions if not understood correctly.

int a = 5;
a += 3 * 2; // a = a + (3 * 2)
Console.WriteLine(a); // Output: 11

In this example, 3 * 2 is evaluated first due to its higher precedence, then the result 6 is added to a.