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C# True and False

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

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.

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.BoolInt, 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

Review.

Most parts of the above program 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.

False.

False is not true. 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

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.BoolBool: ConvertBool: Parse

A true summary.

True and false are commonly used values. They can be stored in a variable of type bool. These 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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