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fmillion
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Writing an extension method for arrays

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I want to write some extension methods for arrays. I'm not quite sure how to approach this.

Suppose I have an array:

byte[] myArray = new byte[24];
// populate byte array here


I want something like

bool areArraysEqual = myArray.CompareTo(anotherArray);


or

byte[] subArray = myArray.Slice(5,3); // offset 5, 3 items


I want to enforce typing, so that if I use the Slice command I can't assign a byte array's Slice to a string array, for example.

I have code written for these methods, with the following method signature:

public static T[] Slice<T>(T[] inArray, int startOffset, int Length)


and

public static bool Compare<T>(T[] a1, T[] a2)


How can I convert these to extension methods that could be called on an array rather than passing references to arrays into the static methods?

fm

extension-method array
  • asked 2 years ago
  • edited 2 years ago
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last answered 2 years ago

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You can do it like this (method implementations just for illustration, not necessarily optimal):

using System;
using ArrayExtensions;

namespace ArrayExtensions
{
   public static class Array2
   {
      public static T[] Slice<T>(this T[] inArray, int startOffset, int Length)
      {       
        T[] outArray = new T[Length];
        Array.Copy(inArray, startOffset, outArray, 0, Length);
        return outArray;
      }

      public static bool Compare<T>(this T[] a1, T[] a2)
      {
         if (a1.Length != a2.Length) return false;
         for (int i = 0; i < a1.Length; i++)
         {
             if (!a1[i].Equals(a2[i])) return false;
         }
         return true;
      }
   }
}

class Test
{
   static void Main()
   {
     byte[] myArray = new byte[24];
     for(byte b = 0; b < 24; b++) myArray[b] = b;
     byte[] anotherArray = new byte[24];
     for(byte b = 0; b < 24; b++) anotherArray[b] = b;
     bool areArraysEqual = myArray.Compare(anotherArray);
     Console.WriteLine(areArraysEqual); // True
     anotherArray[23] = 46;
     areArraysEqual = myArray.Compare(anotherArray);
     Console.WriteLine(areArraysEqual); // False
     byte[] subArray = myArray.Slice(5,3); // offset 5, 3 items
     foreach(byte b in subArray)Console.Write("{0} ", b);
     Console.WriteLine();
     Console.ReadKey();
   }
}

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