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C#: Array
Convert or change

Array.ConvertAll converts an entire array. It converts all elements in one array to another type. We specify the conversion function—this can be done in the lambda expression syntax form.

All extension method

Example. To begin, this example program creates an integer array of three elements on the managed heap. Then, we invoke the Array.ConvertAll static method. You do not need to specify the type parameters, as they are inferred statically.

Static Method

The second argument to Array.ConvertAll is a lambda expression. The identifier 'element' is an argument name, and the lambda function returns the ToString() method result on the element.

Generic MethodToString
C# program that uses Array.ConvertAll method

using System;

class Program
    static void Main()
	// Integer array of three values.
	int[] array1 = new int[3];
	array1[0] = 4;
	array1[1] = 5;
	array1[2] = 6;

	// Use ConvertAll to convert integer array to string array.
	string[] array2 = Array.ConvertAll(array1, element => element.ToString());

	// Write string array.
	Console.WriteLine(string.Join(",", array2));



Framework: NET

Internals. How does the Array.ConvertAll method work inside? First, the second argument can be considered a higher-order procedure. This argument is called each time an element is to be converted.

Note:The ConvertAll method allocates a new array and then places the result of the converter method into each corresponding element slot.

Programming tip

It would be faster to write an imperative method. This would eliminate the delegate method invocations (which are more expensive than regular methods) and the slight overhead that occurs with argument checking.

Summary. The Array.ConvertAll method allows you to declaratively convert an entire array with a single statement. It incurs some performance overhead. But it can simplify code, particularly in programs where many different conversions take place.