Programming Arrays in C#
Programming
C# is a new self-taught series of articles, in which I demonstrate
various topics of C# language in a simple step by step tutorial format.
Arrays
are probably one of the most wanted topics in C#. The focus of this
article is arrays in C#. The article starts with basic definitions of
different array types and how to use them in our application. Later, the
article covers the Arrays class and its methods, which can be used to
sort, search, get, and set an array's items.
Introduction
In C#, an array index starts at zero. That means the first item of an array starts at the 0th position. The position of the last item on an array will total number of items - 1. So if an array has 10 items, the last 10th item is at 9th position.
In C#, arrays can be declared as fixed length or dynamic.
In C#, arrays can be declared as fixed length or dynamic.
A fixed length array can store a predefined number of items.
A dynamic array does not have a predefined size. The size of a dynamic array
increases as you add new items to the array. You can declare an array
of fixed length or dynamic. You can even change a dynamic array to
static after it is defined.
Let's
take a look at simple declarations of arrays in C#. The following code
snippet defines the simplest dynamic array of integer types that does
not have a fixed size.
int[] intArray;
As you can see from the above code snippet, the declaration of an array starts with a type of array followed by a square bracket ([]) and name of the array.
The following code snippet declares an array that can store 5 items only starting from index 0 to 4.
int[] intArray;
intArray = new int[5];
The following code snippet declares an array that can store 100 items starting from index 0 to 99.
int[] intArray;
intArray = new int[100];
Defining arrays of different types
In
the previous code snippet, we saw how to define a simple array of
integer type. Similarly, we can define arrays of any type such as
double, character, and string.
In
C#, arrays are objects. That means that declaring an array doesn't
create an array. After declaring an array, you need to instantiate an
array by using the "new" operator.
The following code snippet defines arrays of double, char, bool, and string data types.
double[] doubleArray = new double[5];
char[] charArray = new char[5];
bool[] boolArray = new bool[2];
string[] stringArray = new string[10];
Initializing Arrays
Once
an array is declared, the next step is to initialize an array. The
initialization process of an array includes adding actual data to the
array.
The following code snippet creates an array of 3 items and values of these items are added when the array is initialized.
// Initialize a fixed array
int[] staticIntArray = new int[3] {1, 3, 5};
Alternative, we can also add array items one at a time as listed in the following code snippet.
// Initialize a fixed array one item at a time
int[] staticIntArray = new int[3];
staticIntArray[0] = 1;
staticIntArray[1] = 3;
staticIntArray[2] = 5;
The following code snippet declares a dynamic array with string values.
// Initialize a dynamic array items during declaration
string[] strArray = new string[] { "Mahesh Chand", "Mike Gold", "Raj Beniwal", "Praveen Kumar", "Dinesh Beniwal" };
Accessing Arrays
We
can access an array item by passing the item index in the array. The
following code snippet creates an array of three items and displays
those items on the console.
// Initialize a fixed array one item at a time
int[] staticIntArray = new int[3];
staticIntArray[0] = 1;
staticIntArray[1] = 3;
staticIntArray[2] = 5;
// Read array items one by one
Console.WriteLine(staticIntArray[0]);
Console.WriteLine(staticIntArray[1]);
Console.WriteLine(staticIntArray[2]);
This
method is useful when you know what item you want to access from an
array. If you try to pass an item index greater than the items in array,
you will get an error.
Accessing an array using a foreach Loop
The
foreach control statement (loop) is used to iterate through the items
of an array. For example, the following code uses foreach loop to read
all items of an array of strings.
// Initialize a dynamic array items during declaration
string[] strArray = new string[] { "Mahesh Chand", "Mike Gold", "Raj Beniwal", "Praveen Kumar", "Dinesh Beniwal" };
// Read array items using foreach loop
foreach (string str in strArray)
{
Console.WriteLine(str);
}
This approach is used when you do not know the exact index of an item in an array and needs to loop through all the items.
Array Types
Arrays can be divided into the following four categories.
· Single-dimensional arrays
· Multidimensional arrays or rectangular arrays
· Jagged arrays
· Mixed arrays.
Single Dimension Arrays
Single-dimensional arrays are the simplest form of arrays. These types of arrays are used to store number of items of a predefined type. All items in a single dimension array are stored contiguously starting from 0 to the size of the array -1.
Single-dimensional arrays are the simplest form of arrays. These types of arrays are used to store number of items of a predefined type. All items in a single dimension array are stored contiguously starting from 0 to the size of the array -1.
The
following code declares an integer array that can store 3 items. As you
can see from the code, first I declare the array using [] bracket and
after that I instantiate the array by calling the new operator.
int[] intArray;
intArray = new int[3];
Array declarations in C# are pretty simple. You put array items in curly braces ({}). If an array is not initialized, its items are automatically initialized to the default initial value for the array type if the array is not initialized at the time it is declared.
The following code declares and initializes an array of three items of integer type.
int[] staticIntArray = new int[3] {1, 3, 5};
The following code declares and initializes an array of 5 string items.
string[] strArray = new string[5] { "Mahesh", "Mike", "Raj", "Praveen", "Dinesh" };
You can even directly assign these values without using the new operator.
string[] strArray = { "Mahesh", "Mike", "Raj", "Praveen", "Dinesh" };
You can initialize a dynamic length array as follows:
string[] strArray = new string[] { "Mahesh", "Mike", "Raj", "Praveen", "Dinesh" };
Multi-Dimensional Arrays
A multi-dimensional array, also known as a rectangular array is an array with more than one dimension. The form of a multi-dimensional array is a matrix.
Declaring a multi-dimensional array
A multi dimension array is declared as following:
string[,] mutliDimStringArray;
A multi-dimensional array can be fixed-sized or dynamic sized.
Initializing multi-dimensional arrays
The
following code snippet is an example of fixed-sized multi-dimensional
arrays that defines two multi dimension arrays with a matrix of 3x2 and
2x2. The first array can store 6 items and second array can store 4
items. Both of these arrays are initialized during the declaration.
int[,] numbers = new int[3, 2] { { 1, 2 }, { 3, 4 }, { 5, 6 } };
string[,] names = new string[2, 2] { { "Rosy", "Amy" }, { "Peter", "Albert" } };
Now let's see examples of multi-dimensional dynamic arrays where you are not sure of the number of items of the array. The following code snippet creates two multi-dimensional arrays with no limit.
int[,] numbers = new int[,] { { 1, 2 }, { 3, 4 }, { 5, 6 } };
string[,] names = new string[,] { { "Rosy", "Amy" }, { "Peter", "Albert" } };
You can also omit the new operator as we did in single dimension arrays. You can assign these values directly without using the new operator. For example:
int[,] numbers = { { 1, 2 }, { 3, 4 }, { 5, 6 } };
string[,] names = { { "Rosy", "Amy" }, { "Peter", "Albert" } };
We
can also initialize the array items one item at a time. The following
code snippet is an example of initializing array items one at a time.
int[,] numbers = new int[3, 2];
numbers[0, 0] = 1;
numbers[1, 0] = 2;
numbers[2, 0] = 3;
numbers[0, 1] = 4;
numbers[1, 1] = 5;
numbers[2, 1] = 6;
Accessing multi-dimensional arrays
A
multi-dimensional array items are represented in a matrix format and to
access it's items, we need to specify the matrix dimension. For
example, item(1,2) represents an array item in the matrix at second row
and third column.
The following code snippet shows how to access numbers array defined in the above code.
Console.WriteLine(numbers[0,0]);
Console.WriteLine(numbers[0, 1]);
Console.WriteLine(numbers[1, 0]);
Console.WriteLine(numbers[1, 1]);
Console.WriteLine(numbers[2, 0]);
Console.WriteLine(numbers[2, 2]);
Jagged Arrays
Jagged arrays are arrays of arrays. The elements of a jagged array are other arrays.
Declaring Jagged Arrays
Declaration
of a jagged array involves two brackets. For example, the following
code snippet declares a jagged array that has three items of an array.
int[][] intJaggedArray = new int[3][];
The following code snippet declares a jagged array that has two items of an array.
string[][] stringJaggedArray = new string[2][];
Initializing Jagged Arrays
Before
a jagged array can be used, its items must be initialized. The
following code snippet initializes a jagged array; the first item with
an array of integers that has two integers, second item with an array of
integers that has 4 integers, and a third item with an array of
integers that has 6 integers.
// Initializing jagged arrays
intJaggedArray[0] = new int[2];
intJaggedArray[1] = new int[4];
intJaggedArray[2] = new int[6];
We can also initialize a jagged array's items by providing the values of the array's items. The following code snippet initializes item an array's items directly during the declaration.
// Initializing jagged arrays
intJaggedArray[0] = new int[2]{2, 12};
intJaggedArray[1] = new int[4]{4, 14, 24, 34};
intJaggedArray[2] = new int[6] {6, 16, 26, 36, 46, 56 };
Accessing Jagged Arrays
We can access a jagged array's items individually in the following way:
Console.Write(intJaggedArray3[0][0]);
Console.WriteLine(intJaggedArray3[2][5]);
We
can also loop through all of the items of a jagged array. The Length
property of an array helps a lot; it gives us the number of items in an
array. The following code snippet loops through all of the items of a
jagged array and displays them on the screen.
// Loop through all itesm of a jagged array
for (int i = 0; i < intJaggedArray3.Length; i++)
{
System.Console.Write("Element({0}): ", i);
for (int j = 0; j < intJaggedArray3[i].Length; j++)
{
System.Console.Write("{0}{1}", intJaggedArray3[i][j], j == (intJaggedArray3[i].Length - 1) ? "" : " ");
}
System.Console.WriteLine();
}
Mixed Arrays
Mixed
arrays are a combination of multi-dimension arrays and jagged arrays.
The mixed arrays type is removed from .NET 4.0. I have not really seen
any use of mixed arrays. You can do anything you want with the help of
multi-dimensional and jagged arrays.
A Simple Example
Here
is a complete example listed in Listing 1 that demonstrates how to
declare all kinds of arrays then initialize them and access them.
To test this code, create a console application using Visual Studio 2010 or Visual C# Express and copy and paste this code.
Console.WriteLine("Single Dimension Array Sample");
// Single dim array
string[] strArray = new string[] { "Mahesh Chand", "Mike Gold", "Raj Beniwal", "Praveen Kumar", "Dinesh Beniwal" };
// Read array items using foreach loop
foreach (string str in strArray)
{
Console.WriteLine(str);
}
Console.WriteLine("-----------------------------");
Console.WriteLine("Multi-Dimension Array Sample");
string[,] string2DArray = new string[2, 2] { { "Rosy", "Amy" }, { "Peter", "Albert" } };
foreach (string str in string2DArray)
{
Console.WriteLine(str);
}
Console.WriteLine("-----------------------------");
Console.WriteLine("Jagged Array Sample");
int[][] intJaggedArray3 =
{
new int[] {2,12},
new int[] {14, 14, 24, 34},
new int[] {6, 16, 26, 36, 46, 56}
};
// Loop through all itesm of a jagged array
for (int i = 0; i < intJaggedArray3.Length; i++)
{
Console.Write("Element({0}): ", i);
for (int j = 0; j < intJaggedArray3[i].Length; j++)
{
Console.Write("{0}{1}", intJaggedArray3[i][j], j == (intJaggedArray3[i].Length - 1) ? "" : " ");
}
Console.WriteLine();
}
Console.WriteLine("-----------------------------");
Listing 1
The output of Listing 1 looks like Figure 1.
Figure 1
No comments:
Post a Comment