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C# Array.Clear ExamplesUse the Array.Clear method to zero out all array elements. Measure the performance of Clear.
Array.Clear. This C# method zeros out elements in a range. It is a one-line, reliable and understandable way to empty or clear your array.
This image shows an array.
Method notes. Clear() works on arrays of any type—including numbers, booleans, structs and class instances. We can provide a start index, and a length.
Array
List Clear
First example. Many arrays use integers or other value types such as char. In the C# language, these types of arrays are always initialized to 0.
Program We use Array.Clear to reset all elements in an int array to zero, without reallocating the array or changing its reference.
Length We use the Length property of the array as the third argument. This clears all elements.
Array Length
This image shows an array.
using System; class Program { static void Main() { int[] integerArray = { 4, 6, 8, 1, 3 }; Console.WriteLine(string.Join(",", integerArray)); // Clear all elements in the array. Array.Clear(integerArray, 0, integerArray.Length); Console.WriteLine(string.Join(",", integerArray)); } }
4,6,8,1,3 0,0,0,0,0
Example 2. This example shows an array of objects, each with 2 properties. The Array.Clear method is used to set the first 2 references in the array to null.
Null
Here The first argument to Array.Clear is the target array to clear. And the second specifies the offset to start clearing at.
Tip The third argument uses Math.Min to clear either 2 elements or all elements, whichever is smaller.
Also If you clear 2 elements and the array has one element, you will get an error. Math.Min prevents this exception.
Math.Max, Min
using System; class Program { class Employee { public string Name { get; set; } public int Salary { get; set; } } static void Main() { Employee[] employees = new Employee[3]; employees[0] = new Employee() { Name = "Bob", Salary = 10000 }; employees[1] = new Employee() { Name = "Susan", Salary = 13000 }; employees[2] = new Employee() { Name = "John", Salary = 20000 }; // // Display the employee array. // Console.WriteLine("--- Employee array before ---"); foreach (Employee employee in employees) { Console.Write(employee.Name); Console.Write(": "); Console.WriteLine(employee.Salary); } // // Clear first two elements in employee array. // Array.Clear(employees, 0, Math.Min(2, employees.Length)); // // Display the employee array. // Console.WriteLine("--- Employee array after ---"); foreach (Employee employee in employees) { if (employee != null) { Console.Write(employee.Name); Console.Write(": "); Console.WriteLine(employee.Salary); } else { Console.WriteLine("null"); } } } }
--- Employee array before --- Bob: 10000 Susan: 13000 John: 20000 --- Employee array after --- null null John: 20000
Performance, Array.Clear. Here we test the performance of the Array.Clear method. Logically, Array.Clear could be implemented with a for-loop.
Version 1 The Array.Clear method is invoked. It clears the 128-element int array that was allocated as a local variable.
Version 2 Here we use a for-loop and assign each element to zero. We time this version and the previous version.
Result In 2021 with .NET 5 for Linux, Array.Clear is much faster—Clear() has apparently undergone some performance optimizations.
using System; using System.Diagnostics; class Program { const int _max = 10000; static void Main() { int[] array = new int[128]; // Version 1: clear with Array.Clear. var s1 = Stopwatch.StartNew(); for (int i = 0; i < _max; i++) { Array.Clear(array, 0, array.Length); } s1.Stop(); // Version 2: clear with for-loop. var s2 = Stopwatch.StartNew(); for (int i = 0; i < _max; i++) { for (int z = 0; z < array.Length; z++) { array[z] = 0; } } s2.Stop(); Console.WriteLine(((double)(s1.Elapsed.TotalMilliseconds * 1000000) / _max).ToString("0.00 ns")); Console.WriteLine(((double)(s2.Elapsed.TotalMilliseconds * 1000000) / _max).ToString("0.00 ns")); } }
14.45 ns Array.Clear 107.94 ns for
A discussion. Boolean arrays are cleared by having all their elements assigned to false. Also, struct arrays will be cleared the same way as other arrays of System.ValueType instances.
Note All struct fields will be set to null or 0, depending on their type. The default value can be found with the default operator.
Struct
Default
A summary. Array.Clear is frequently useful in programs. It is a one-line way of resetting your entire array to its default values. It works on arrays of values and references.
Dot Net Perls is a collection of tested code examples. Pages are continually updated to stay current, with code correctness a top priority.
Sam Allen is passionate about computer languages. In the past, his work has been recommended by Apple and Microsoft and he has studied computers at a selective university in the United States.
This page was last updated on 12/16/2021 (edit).
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