如何从C#中的2D数组中获取完整的行或列 [英] How to get a complete row or column from 2D array in C#

问题描述

我不想使用锯齿状数组，而我有一个2D数组，我想获得完整的列或行而不循环遍历它.有谁知道如何做到这一点.

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 

推荐答案

您可以使用Buffer.BlockCopy()对其进行优化，以获取行，但是必须循环获取列. Buffer.BlockCopy()最终使用处理器指令来复制一块内存，因此速度非常快.

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.

将代码放入扩展方法很方便，以便于调用.请注意，Buffer.BlockCopy()仅可用于基本类型的数组，即int，double，char等.这不包括string.

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.

这是一个可编译的示例:

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;
        }
   }
}

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