How to get a complete row or column from 2D array in C#

Question

I do not want to use a jagged array and I have a 2D array and I want to get a complete column or row without looping through it. Does anyone have an idea how it can be done.

double [,]  array = new double [3,3] ;  1   2   3  4   5   6  Out: 1   2   3  or 2   5  

Answer 1

To get a specific row or column from the multidimensional array you can use some LINQ:

public class CustomArray<T> {     public T[] GetColumn(T[,] matrix, int columnNumber)     {         return Enumerable.Range(0, matrix.GetLength(0))                 .Select(x => matrix[x, columnNumber])                 .ToArray();     }      public T[] GetRow(T[,] matrix, int rowNumber)     {         return Enumerable.Range(0, matrix.GetLength(1))                 .Select(x => matrix[rowNumber, x])                 .ToArray();     } } 

Answer 2

You can optimise it for getting rows by using Buffer.BlockCopy(), but to get a column you'll have to loop. Buffer.BlockCopy() ultimately uses a processor instruction to copy a block of memory, so it is pretty fast.

It's convenient to put the code into an extension method to make it easier to call. Note that Buffer.BlockCopy() can only be used on arrays of primitive types, i.e. int, double, char etc. This does NOT include string.

Here's a compilable example:

using System; using System.Linq; using System.Runtime.InteropServices;  namespace ConsoleApplication4 {     public static class Program     {         private static void Main()         {             var array = new [,]             {                 {0.1, 0.2, 0.3, 0.4, 0.5},                 {1.1, 1.2, 1.3, 1.4, 1.5},                 {2.1, 2.2, 2.3, 2.4, 2.5},                 {3.1, 3.2, 3.3, 3.4, 3.5},             };              var row = array.GetRow(2);              // This prints 2.1, 2.2, 2.3, 2.4, 2.5              Console.WriteLine(string.Join(", ", row.Select(element => element.ToString())));         }     }      public static class ArrayExt     {         public static T[] GetRow<T>(this T[,] array, int row)         {             if (!typeof(T).IsPrimitive)                 throw new InvalidOperationException("Not supported for managed types.");              if (array == null)                 throw new ArgumentNullException("array");              int cols = array.GetUpperBound(1) + 1;             T[] result = new T[cols];              int size;              if (typeof(T) == typeof(bool))                 size = 1;             else if (typeof(T) == typeof(char))                 size = 2;             else                 size = Marshal.SizeOf<T>();              Buffer.BlockCopy(array, row*cols*size, result, 0, cols*size);              return result;         }    } }