Array concatenation in C#

Question

1. How do I smartly initialize an Array with two (or more) other arrays in C#?

   double[] d1 = new double[5];
   double[] d2 = new double[3];
   double[] dTotal = new double[8]; // I need this to be {d1 then d2}
   

2. Another question: How do I concatenate C# arrays efficiently?

Answer 1

You could use CopyTo:

double[] d1 = new double[5];
double[] d2 = new double[3];
double[] dTotal = new double[d1.Length + d2.Length];

d1.CopyTo(dTotal, 0);
d2.CopyTo(dTotal, d1.Length);

Answer 2

var dTotal = d1.Concat(d2).ToArray();

You could probably make it 'better' by creating dTotal first, and then just copying both inputs with Array.Copy.

Answer 3

You need to call Array.Copy, like this:

double[] d1 = new double[5];
double[] d2 = new double[3];
double[] dTotal = new double[d1.length + d2.length];

Array.Copy(d1, 0, dTotal, 0, d1.Length);
Array.Copy(d2, 0, dTotal, d1.Length, d2.Length);

Answer 4

using System.Linq;

int[] array1 = { 1, 3, 5 };
int[] array2 = { 0, 2, 4 };

// Concat array1 and array2.
var result1 = array1.Concat(array2).ToArray();