How to Convert int[] to int[,] - C#

Question

I have an int array in one dimension:

var intArray=new[] { 1, 2, 3, 4, 5, 6 };

and I want to convert it to two dimensions, such as:

var intArray2D=new[,] { {1, 2}, {3, 4}, {5, 6} };

How do I achieve this with C#?

Answer 1

with a loop perhaps:

for (int i = 0; i < oldArr.Length; i=i+2)
{
    newArr[i/2, 0] = oldArr[i];
    newArr[i/2, 1] = oldArr[i + 1];
}

Untested, but should get you pointed in the right direction...

Answer 2

If the one dimensional array contains the primitive data in row major order, and the total capacity of the 2 dimensional array equals the length of the one dimensional array, you can use this.

int[] source = new int[6];
int[,] target = new int[3, 2];
Buffer.BlockCopy(source, 0, target, 0, source.Length * sizeof(int));

Note that unlike Array.Copy and other array/list methods, Buffer.BlockCopy operates on a number of bytes of data, even if each element of the array is larger than 1 byte. It also only operates on arrays of primitive data types.

Additional references:

• Multi-dimensional arrays are stored in row-major order (ECMA-335 Partition I, §8.9.1)
• Buffer.BlockCopy

Edit: Here is a complete unit test.

[TestMethod]
public void SOTest16203210()
{
    int[] source = new int[6] { 1, 2, 3, 4, 5, 6 };
    int[,] destination = new int[3, 2];
    Buffer.BlockCopy(source, 0, destination, 0, source.Length * sizeof(int));
    Assert.AreEqual(destination[0, 0], 1);
    Assert.AreEqual(destination[0, 1], 2);
    Assert.AreEqual(destination[1, 0], 3);
    Assert.AreEqual(destination[1, 1], 4);
    Assert.AreEqual(destination[2, 0], 5);
    Assert.AreEqual(destination[2, 1], 6);
}