TL;DR – C# switch statement is for comparing a specific condition against three or more possible cases.
Contents
Principles of the switch Statement
C# switch is a selection statement for choosing a switch section matching the specified pattern. In other words, this statement tests whether a match expression equals any of the enumerated cases.
Tip: the match expression refers to the expression to be checked. Each condition is referred to as the C# switch case. The keyword case defines a statement. The value after the statement is a label.
Here is an illustration of the structure of the C# switch statement:
The following code example shows the use of the C# switch statement. Our code presents three possible cases, depending on the way people answer a question:
using System;
public class Example
{
public static void Main()
{
char answers = 'K';
switch (answers)
{
case 'N':
Console.WriteLine("Not pleased with the current services.");
break;
case 'Y':
Console.WriteLine("Pleased with the current services.");
break;
case 'E':
Console.WriteLine("No answer to this question.");
break;
default:
Console.WriteLine("Invalid answer.");
break;
}
}
}The presented expression is N, and it corresponds to the Case 'N', meaning that the console will print the appropriate phrase.
Tip: the keyword break exits the case section. Be sure to include it for better functionality.
Additionally, you can include a default case for when the match expression does not match any of the other C# switch cases:
using System;
public class Example
{
public static void Main()
{
char answers = 'K';
switch (answers)
{
case 'N':
Console.WriteLine("Not pleased with the current services.");
break;
case 'Y':
Console.WriteLine("Pleased with the current services.");
break;
case 'E':
Console.WriteLine("No answer to this question.");
break;
default:
Console.WriteLine("Invalid answer.");
break;
}
}
}Remember: single switch statement can only have one default case.
In this C# switch example, we generate a random match expression from the specified desserts. Then, the switch statement delivers the corresponding case and its label to the console:
using System;
public enum Dessert
{
Cake,
Milkshake,
Candy
}
public class Example
{
public static void Main()
{
Dessert d = (Dessert)(new Random()).Next(0, 4);
switch (d)
{
case Dessert.Cake:
Console.WriteLine("The dessert is a cake");
break;
case Dessert.Milkshake:
Console.WriteLine("The dessert is a milkshake");
break;
case Dessert.Candy:
Console.WriteLine("The dessert is a candy");
break;
default:
Console.WriteLine("No dessert for you");
break;
}
}
}Governing Types
The switch expression determines the governing type for the entire switch statement C#:
- When the switch expression is
sbyte,byte,short,int,ushort,uint,long,ulong,bool,char,string,enum_type, then that type becomes the governing type of the statement. The same applies to nullable types related to the mentioned types. - In other cases, a conversion from the switch expression type to one of the possible governing types must occur (or to a nullable type).
- If a conversion does not take place or if multiple conversions occur, the compiler generates an error.
The governing type of a switch statement can be a string. This C# switch example illustrates this:
using System;
public class Example
{
public static void Main()
{
string str = "Yes, I have";
switch (str)
{
case "Yes, I have":
Console.WriteLine("The person has participated in this activity.");
break;
case "No, I have not":
Console.WriteLine("The person has not participated in this activity.");
break;
case "I don't know":
Console.WriteLine("The person does not know.");
break;
default:
Console.WriteLine("The person did not respond.");
break;
}
}
}In this example of C# switch string type, we reveal how to make the match expression as a string.
Note: switch C# cannot have duplicate cases. Otherwise, compilers show an error.
The switch Statement and Patterns
Before the release of C# 7.0, it was necessary to define value and check it against the specified cases. After the new version was released, the switch statement C# allows comparing the value of switch with the value delivered by an expression, not the fixed value.
using System;
public class Example
{
public static void Main()
{
Console.WriteLine("Available hotel rooms: 1=one room apartament 2=two room apartament 3=three room apartament");
Console.Write("Please choose your hotel room: ");
string str = Console.ReadLine();
int cost = 0;
// Due to the goto statements in 2 and 3 cases, the base cost
// cents is added to the additional cost for the two-room and three-room apartments.
switch (str)
{
case "1":
case "one room apartament":
cost += 15;
break;
case "2":
case "two room apartament":
cost += 15;
goto case "1";
case "3":
case "three room apartament":
cost += 15;
goto case "2";
default:
Console.WriteLine("Invalid selection. Please select 1, 2, or 3 and try again.");
break;
}
if (cost != 0)
{
Console.WriteLine("You need to pay {0} dollars.", cost);
}
Console.WriteLine("Thank you for booking in our hotel!");
}
}Every switch case C# specifies a condition or a statement which is compared to the match expression. Once it finds a match, the switch section is executed. This feature is available in all versions from C# 7.0.
C# switch: Useful Tips
- If you are testing an expression against two cases, you should apply
if-elsestatement instead. - If the C# switch does not have a default case, then the code won’t be executed when there are no matches.
- Since C# does not permit the code to run from one case label to another, you have to use
break. However, this is not the only option. Considergotoorreturn.