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{{wikibooks|Computer Science Design Patterns|Chain of responsibility|Chain-of-responsibility implementations in various languages}}
 
=== C# example ===
This C# examples uses the logger application to select different sources based on the log level;
 
<syntaxhighlight lang="C#">
namespace ChainOfResponsibility;
 
[Flags]
public enum LogLevel
{
None = 0, // 0
Info = 1, // 1
Debug = 2, // 10
Warning = 4, // 100
Error = 8, // 1000
FunctionalMessage = 16, // 10000
FunctionalError = 32, // 100000
All = 63 // 111111
}
 
/// <summary>
/// Abstract Handler in chain of responsibility pattern.
/// </summary>
public abstract class Logger
{
protected LogLevel logMask;
 
// The next Handler in the chain
protected Logger next;
 
public Logger(LogLevel mask)
{
this.logMask = mask;
}
 
/// <summary>
/// Sets the Next logger to make a list/chain of Handlers.
/// </summary>
public Logger SetNext(Logger nextlogger)
{
Logger lastLogger = this;
 
while (lastLogger.next != null)
{
lastLogger = lastLogger.next;
}
 
lastLogger.next = nextlogger;
return this;
}
 
public void Message(string msg, LogLevel severity)
{
if ((severity & logMask) != 0) // True only if any of the logMask bits are set in severity
{
WriteMessage(msg);
}
if (next != null)
{
next.Message(msg, severity);
}
}
 
abstract protected void WriteMessage(string msg);
}
 
public class ConsoleLogger : Logger
{
public ConsoleLogger(LogLevel mask)
: base(mask)
{ }
 
protected override void WriteMessage(string msg)
{
Console.WriteLine("Writing to console: " + msg);
}
}
 
public class EmailLogger : Logger
{
public EmailLogger(LogLevel mask)
: base(mask)
{ }
 
protected override void WriteMessage(string msg)
{
// Placeholder for mail send logic, usually the email configurations are saved in config file.
Console.WriteLine("Sending via email: " + msg);
}
}
 
class FileLogger : Logger
{
public FileLogger(LogLevel mask)
: base(mask)
{ }
 
protected override void WriteMessage(string msg)
{
// Placeholder for File writing logic
Console.WriteLine("Writing to Log File: " + msg);
}
}
 
public class Program
{
public static void Main(string[] args)
{
// Build the chain of responsibility
Logger logger;
logger = new ConsoleLogger(LogLevel.All)
.SetNext(new EmailLogger(LogLevel.FunctionalMessage | LogLevel.FunctionalError))
.SetNext(new FileLogger(LogLevel.Warning | LogLevel.Error));
 
// Handled by ConsoleLogger since the console has a loglevel of all
logger.Message("Entering function ProcessOrder().", LogLevel.Debug);
logger.Message("Order record retrieved.", LogLevel.Info);
 
// Handled by ConsoleLogger and FileLogger since filelogger implements Warning & Error
logger.Message("Customer Address details missing in Branch DataBase.", LogLevel.Warning);
logger.Message("Customer Address details missing in Organization DataBase.", LogLevel.Error);
 
// Handled by ConsoleLogger and EmailLogger as it implements functional error
logger.Message("Unable to Process Order ORD1 Dated D1 For Customer C1.", LogLevel.FunctionalError);
 
// Handled by ConsoleLogger and EmailLogger
logger.Message("Order Dispatched.", LogLevel.FunctionalMessage);
}
}
/* Output
Writing to console: Entering function ProcessOrder().
Writing to console: Order record retrieved.
Writing to console: Customer Address details missing in Branch DataBase.
Writing to Log File: Customer Address details missing in Branch DataBase.
Writing to console: Customer Address details missing in Organization DataBase.
Writing to Log File: Customer Address details missing in Organization DataBase.
Writing to console: Unable to Process Order ORD1 Dated D1 For Customer C1.
Sending via email: Unable to Process Order ORD1 Dated D1 For Customer C1.
Writing to console: Order Dispatched.
Sending via email: Order Dispatched.
*/
</syntaxhighlight>
 
=== Crystal example ===
Retrieved from "https://en.wikipedia.org/wiki/Chain-of-responsibility_pattern"