case Example
This page was last reviewed on Oct 26, 2023.
Dot Net Perls
Case. This C# keyword is part of switch. We use this keyword to match constant values in switches. Case specifies a constant to be matched in the switch selection statement.
Usage. Cases can be stacked and combined. We can target a case with a goto statement. And "default" is a special kind of case—it is matched when nothing else does.
Simple example. Cases specify constants that match the selection in a switch statement. The blocks following a specific case statement are only executed when the case constants are matched.
Info Default matches all values that are not matched by the specified case statements. It is like "else" in an if-else chain.
using System; int test = 5; string result = null; switch (test) { case 5: result = "Five"; break; default: result = "Not five"; break; } Console.WriteLine(result);
Complex example. Here is a more complex example. This code demonstrates the case keyword used in different ways. A string switch statement is shown.
String switch
Detail The first 3 cases are stacked on top of each other. This syntax can match multiple cases to a single executable code block.
Note At the end of each case statement block, you must have a break, return or go to jump statement for the program to compile.
Detail The default case does not use the "case" keyword. It is the case that is matched when no other cases do.
using System; class Program { static string TestCase(string value) { const string _special = "constant"; // Begin the switch. switch (value) { case "100": case "1000": case "10000": { // You can use the parentheses in a case body. return "Multiple of ten"; } case "500": case "5000": case "50000": // You can omit the parentheses and stack the cases. return "Multiple of fifty"; case _special: // You can use a constant identifier in the case. return "*"; default: // You can use the default case. return "Invalid"; } } static void Main() { // Test the method. Console.WriteLine(TestCase("100")); Console.WriteLine(TestCase("1000")); Console.WriteLine(TestCase("5000")); Console.WriteLine(TestCase("constant")); Console.WriteLine(TestCase(null)); } }
Multiple of ten Multiple of ten Multiple of fifty * Invalid
Constant expected. It is important to know what values are constant before using them in a switch. For example, string.Empty is not constant—it is a field.
So We cannot use string.Empty in a case statement. Other fields in a class also cannot be cases.
Detail The C# compiler will report the error to us before the program is ever run. This is helpful.
class Program { static void Main(string[] args) { switch (args[0]) { case string.Empty: break; } } }
Error CS0150 A constant value is expected
Syntax tip. It is possible to omit the surrounding parentheses in a case block. This option is useful for large or deeply nested switches, or switch statements that have many short blocks.
And There is no difference in the compiled program if you omit the parentheses.
Also The switch statement also shows how to use a constant field or local constant in the case statements.
Detail The C# compiler will internally treat this constant the same way as explicitly specified constants in other cases.
Fall-through. The C# language does not allow cases to fall through to the next cases. This means you cannot execute separate code blocks in multiple case statements.
But You can still stack together multiple cases. This limitation was added to the language to reduce programming mistakes.
A summary. Case is used in switch statements. We also find this keyword in certain goto statements. The case statement is specified with a constant, which may be defined elsewhere.
Dot Net Perls is a collection of tested code examples. Pages are continually updated to stay current, with code correctness a top priority.
Sam Allen is passionate about computer languages. In the past, his work has been recommended by Apple and Microsoft and he has studied computers at a selective university in the United States.
This page was last updated on Oct 26, 2023 (edit).
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