C# True and False

Understand the true and false keywords. See example programs that use if-statements and bools.

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True, false. True and false are boolean literals. They are values that mean yes and no. They can be stored in variables of type bool.Bool

In the C# language, true and false are lowercase reserved keywords. We cannot specify true and false with integers directly—0 and 1 are not compatible.Int, uint

True. We look at a program that uses the true keyword. We can use true in if-statements, while-statements, expressions, assignments and negations.IfWhile
Tip: In the C# language, the if-statement requires that its expression be evaluated in a bool context.
And: This means you may sometimes need to explicitly specify the comparison—you cannot directly test integers.
C# program that uses true using System; class Program { static void Main() { // Reachable. if (true) { Console.WriteLine(1); } // Expressions can evaluate to true or false. if ((1 == 1) == true) { Console.WriteLine(2); } // While true loop. while (true) { Console.WriteLine(3); break; } // Use boolean to store true. bool value = true; // You can compare bool variables to true. if (value == true) { Console.WriteLine(4); } if (value) { Console.WriteLine(5); } } } Output 1 2 3 4 5

False. The false keyword is a constant boolean literal, meaning it is a value that can be stored in a variable. It can also be evaluated in an if-expression.
First: In the first if-statement, we see that when an expression evaluates to false, the code inside the if-block is not reached.
Bool: You can set a bool variable to false. You can invert the value of a bool variable with the exclamation operator.
Finally: The expression != false is equal to == true. This can be entirely omitted.
Tip: It is usually clearer to express conditions in terms of truth rather than testing against false, but sometimes false may be clearer.
C# program that uses false literal using System; class Program { static void Main() { // Unreachable. if (false) { Console.WriteLine(); // Not executed. } // Use boolean to store true and false. bool value = true; Console.WriteLine(value); // True value = false; Console.WriteLine(value); // False value = !value; Console.WriteLine(value); // True // Expressions can be stored in variables. bool result = (1 == int.Parse("1")) != false; Console.WriteLine(result); // True } } Output True False True True

Review. Most parts of true and false are clear to understand. You can change the value of a bool that is set from assignment to an expression by applying a == true or != true at the end.
Frequent: The true keyword is very frequently used. There are some subtleties to its use, particularly in assignments to expressions.
Tip: If-statements and while-statements require a bool processing context, which mandates the usage of true—or false.

Bool. True and false are stored in bool variables. Bools are not directly convertible to value types such as int. Instead, a special conversion method must be used.Bool: ConvertBool: Parse

A summary. True and false are commonly used values. They can be stored in a variable of type bool. These 2 keywords are boolean literals.

They can be used anywhere a boolean expression is used. This includes an if-statement or a while-loop. True and false cannot be directly converted to other values such as 1 and 0.


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