ToArray

This method converts types to arrays. It forces the evaluation of query expressions and IEnumerable types. It returns an array of the same type.

Implemented in System.Linq, ToArray reduces program length and increases program simplicity. But we must be careful not to call ToArray when it is not needed.

Example

The ToArray extension method is a generic method that internally allocates a Buffer array where the elements are copied. We often use it alongside query expressions.

using System;
using System.Linq;

// Step 1: create an array.
int[] array1 = { 5, 1, 4 };

// Step 2: use query expression on array.
var query = from element in array1
                 orderby element
                 select element;

// Step 3: convert expression to array variable.
int[] array2 = query.ToArray();

// Step 4: display array.
foreach (int value in array2)
{
    Console.WriteLine(value);
}
1
4
5

ToArray, same statement

Suppose we have a query expression, and we want to have an array. We can call ToArray directly on the query expression, which forces its evaluation.

using System;
using System.Linq;

class Program
{
    static void PrintArrayLength(int[] array)
    {
        Console.WriteLine("ARRAY LENGTH: {0}", array.Length);
    }

    static void Main()
    {
        int[] elements = { 10, 20, 30 };
        // Use ToArray directly on query.
        PrintArrayLength((from e in elements
                          where e >= 20
                          select e).ToArray());
    }
}
ARRAY LENGTH: 2

Not always needed

We can sometimes avoid using ToArray. Suppose want to Join together the strings in a string List. We can directly pass the List to string.Join.

using System;
using System.Collections.Generic;

class Program
{
    static void Main()
    {
        var items = new List<string>() { "test", "deploy", "script" };
        // We can use string.Join without ToArray.
        Console.WriteLine("NO TOARRAY: {0}", string.Join("+", items));
        Console.WriteLine("   TOARRAY: {0}", string.Join("+", items.ToArray()));
    }
}
NO TOARRAY: test+deploy+script
   TOARRAY: test+deploy+script

Discussion

There are other ToArray methods. It is important to realize that the "ToArray" method identifier is used by various different implementations on different types.

ToArray converts an enumerable types into an array. It can act upon a query expression variable. It forces evaluation of a query expression.