One of the topics many junior programmers struggle with is delegates. And today, anonymous delegates and lambda expressions are profuse in .net APIs. To help some VB programmers adapt to C# and the many equivalent flavors of delegates, I walked through some simple samples to show them the different flavors of delegates.
using System;
using System.Collections.Generic;
using System.Linq;
namespace DelegateExample
{
class Program
{
public delegate string ProcessStringDelegate(string data);
public static string ReverseStringStaticMethod(string data)
{
return
new String(data.Reverse().ToArray());
}
static void Main(string[] args)
{
var stringDelegates =
new List<ProcessStringDelegate>
{
//==========================================================
// Declare a
new delegate instance and pass the name of the method in
new ProcessStringDelegate(ReverseStringStaticMethod),
//==========================================================
// A shortcut is to just and pass the name of the method in
ReverseStringStaticMethod,
//==========================================================
// You can create an anonymous delegate also
delegate (string inputString) //Scramble
{
var outString = inputString;
if (!string.IsNullOrWhiteSpace(inputString))
{
var rand =
new Random();
var chs = inputString.ToCharArray();
for (int i = 0; i < inputString.Length * 3; i++)
{
int x = rand.Next(chs.Length), y = rand.Next(chs.Length);
char c = chs[x];
chs[x] = chs[y];
chs[y] = c;
}
outString =
new string(chs);
}
return outString;
},
//==========================================================
// yet another syntax would be the lambda expression syntax
inputString => { // ROT13
var array = inputString.ToCharArray();
for (int i = 0; i < array.Length; i++)
{
int n = (int)array[i];
n += (n >= 'a' && n <= 'z') ?
((n > 'm') ? 13 : -13) :
((n >= 'A' && n <= 'Z') ?
((n > 'M') ? 13 : -13) : 0);
array[i] = (char)n;
}
return
new string(array);
}
//==========================================================
};
// Display the results of the delegate calls
var stringToTransform = "Welcome to the jungle!";
System.Console.ForegroundColor = ConsoleColor.Cyan;
System.Console.Write("String to Process: ");
System.Console.ForegroundColor = ConsoleColor.Yellow;
System.Console.WriteLine(stringToTransform);
stringDelegates.ForEach(delegatePointer =>
{
System.Console.WriteLine();
System.Console.ForegroundColor = ConsoleColor.Cyan;
System.Console.Write("Delegate Method Name: ");
System.Console.ForegroundColor = ConsoleColor.Magenta;
System.Console.WriteLine(delegatePointer.Method.Name);
System.Console.ForegroundColor = ConsoleColor.Cyan;
System.Console.Write("Delegate Result: ");
System.Console.ForegroundColor = ConsoleColor.White;
System.Console.WriteLine(delegatePointer(stringToTransform));
});
System.Console.ReadKey();
}
}
}
The output of the program is below:
String to Process: Welcome to the jungle!
Delegate Method Name: ReverseStringStaticMethod
Delegate Result: !elgnuj eht ot emocleW
Delegate Method Name: ReverseStringStaticMethod
Delegate Result: !elgnuj eht ot emocleW
Delegate Method Name: b__1
Delegate Result: cg ljotWotem!le une eh
Delegate Method Name: b__2
Delegate Result: dX_V|`X ?| ?[X ]?{Z_X!
