What is the difference between | and || operators in c#?

The || is called logical OR operator and | is called bitwise logical OR operator. The key difference between them lies in how they evaluate expressions and when they stop execution.

Syntax

Both operators have similar syntax −

bool_exp1 || bool_exp2  // Logical OR (short-circuit)
bool_exp1 | bool_exp2   // Bitwise OR (always evaluates both)

Key Differences

Using Logical OR (||) - Short-Circuit Evaluation

The || operator uses short-circuit evaluation. If the first condition is true, the second condition is not evaluated because the result is already determined −

using System;

namespace DemoApplication {
    public class Program {
        static void Main(string[] args) {
            if(Condition1() || Condition2()) {
                Console.WriteLine("Logical OR If Condition Executed");
            }
        }
        
        static bool Condition1() {
            Console.WriteLine("Condition 1 executed");
            return true;
        }
        
        static bool Condition2() {
            Console.WriteLine("Condition 2 executed");
            return true;
        }
    }
}

The output of the above code is −

Condition 1 executed
Logical OR If Condition Executed

Notice that Condition2() is never called because Condition1() returned true.

Using Bitwise OR (|) - Always Evaluates Both

The | operator always evaluates both expressions regardless of the first expression's result −

using System;

namespace DemoApplication {
    public class Program {
        static void Main(string[] args) {
            if(Condition1() | Condition2()) {
                Console.WriteLine("Bitwise OR If Condition Executed");
            }
        }
        
        static bool Condition1() {
            Console.WriteLine("Condition 1 executed");
            return true;
        }
        
        static bool Condition2() {
            Console.WriteLine("Condition 2 executed");
            return true;
        }
    }
}
}

The output of the above code is −

Condition 1 executed
Condition 2 executed
Bitwise OR If Condition Executed

Both conditions are executed even though the first one returned true.

Bitwise OR with Integer Values

The | operator is also used for bitwise operations on integer types −

using System;

namespace DemoApplication {
    public class Program {
        static void Main(string[] args) {
            int a = 5;   // Binary: 101
            int b = 3;   // Binary: 011
            int result = a | b;  // Binary: 111 = 7
            
            Console.WriteLine($"5 | 3 = {result}");
            Console.WriteLine($"Binary: 101 | 011 = {Convert.ToString(result, 2)}");
        }
    }
}

The output of the above code is −

5 | 3 = 7
Binary: 101 | 011 = 111

When to Use Which Operator

• Use || for boolean logic where you want efficient short-circuit evaluation.

• Use | for bitwise operations on integer types or when you need both expressions to execute.

• In most boolean conditions, || is preferred for better performance.

Conclusion

The || operator provides short-circuit evaluation for boolean expressions, making it more efficient by stopping evaluation once the result is determined. The | operator always evaluates both operands and is primarily used for bitwise operations, though it can also work with boolean values when you need both expressions to execute.