Statements #
The if, for, while, and do while statements look identical to those in C++. The only difference is the logical condition in these statements, which must evaluate to a boolean value.
The switch statement
#
Unlike in C++, the switch statement in C# does not allow control to fall through from one case block to the next implicitly. However, you can attach multiple case labels to a single block.
In addition to matching constants, the switch statement can use pattern matching for any pattern. More on patterns later.
Additionally, after the pattern, we can provide an additional condition that will be considered after the pattern is checked.
switch (expression)
{
case pattern:
statement list
case pattern:
case pattern when condition: // optional case guard
statement list
default:
statement list
}An example of a statement with the two most commonly used types of patterns and an optional condition:
void TellMeAboutTheObject(object obj)
{
switch (obj)
{
case 0: // constant pattern
Console.WriteLine("It's a zero.");
break;
case string str: // type pattern
Console.WriteLine($"It's a string: {str}");
break;
// type pattern with case guard
case DateTime dt when dt.DayOfWeek == DayOfWeek.Monday:
Console.WriteLine("It's a Monday");
break;
default:
Console.WriteLine("IDK");
break;
}
}The switch expression
#
The switch expression is more concise and is used to return a single value based on pattern matching.
In this case, every case must be handled; otherwise, the runtime throws an exception. The equivalent of default in a switch expression is the discard pattern _.
type variable = input expression switch
{
pattern => candidate expression ,
pattern when condition => candidate expression ,
pattern => candidate expression
}Example:
string cardName = cardNumber switch
{
13 => "King", // constant pattern
12 => "Queen",
11 => "Jack",
> 1 and < 11 => "Pip card", // relational pattern
1 => "Ace",
// discard pattern, equivalent of default:
_ => throw new ArgumentOutOfRangeException()
};The foreach statement
#
Similar to C++, in C# we have a range for loop, but with a slightly different syntax. It can be used on anything that is iterable. For example, all built-in collections, arrays, and strings are iterable. We will discuss what makes something iterable later.
int[] array = new int[] {0, 1, 2, 3, 4};
foreach (var i in array)
Console.WriteLine(i);
foreach (char c in "foreach")
Console.WriteLine(c);