2D Arrays in C# with Examples

In this article, I am going to discuss the 2D Arrays in C# with Examples. Please read our previous article before proceeding to this article where we discussed One-Dimensional Arrays in C# with Examples.

What is a Two-Dimensional Array in C#?

The arrays which store the elements in the form of rows and columns are called Two-Dimensional Array in C#. The two-dimensional array which is also called a multidimensional array is of two types in C#. They are as follows

1. Rectangular Array: The array whose rows and columns are equal is called a rectangular array
2. Jagged Array: The array whose rows and columns are not equal is called a jagged array

Rectangular 2D Arrays in C#:

A two-dimensional array is an array in which each element is referred to by two indexes. Element in the 2D array is stored in the matrix form. The first index shows the row of the matrix and the second index shows the column of the matrix.

Example: int[,] matrix = new int[3,3];

2D Array in Memory Representation is shown below. To access elements in the zeroth index we need to specify two indexes matrix[0][0].

How 2D Array is Created and Accessed in C#?

The method for creating a rectangular two-dimensional array is as follows:
int[,] A = new int[3,4];
If we created it like this, then the 2D array is created with 3 rows and 4 columns where the name of the array is A. For a better understanding, please have a look at the below diagram.

Here, j represents the row number and i represents the column number. As we created the array with sizes 3 and 4, here you can see that the array is created with 3 rows and 4 columns. We can access any element with the row and column number as follows:
Console.WriteLine(A[1,2]);
This means the 2nd row and 3rd column as Array Indexed are 0-based indexes.

Note: Indexing starts from 0 onwards in the array. So, we have started the row and column from 0. This is how we can access any location. Addressing of 2d array is mapped the same as single dimension array.

Memory Locations are allocated continuously side by side. So basically, it will create a single dimension array of size 12, where the first four locations are used as the first rows, the second four locations are used as the second row and the rest four locations are used as the third row. So, in a computer the memory is represented as follows:

But the compiler will allow us to access this single-dimension array as a 2D array. Next, let us see how to create and initialize a 2D array.

Initializing a 2Dimensional Array in C#:

Let us understand how to initialize a 2D Array with an example. Please have a look at the following statement which shows the declaration and initialization of a 2D Array.
int[,] A = {{2, 5, 9},{6, 9, 15}};
This is the declaration + initialization of a 2Dimensinal array in C#. Here 2,5,9 is the 1st row and 6,9,15 is the 2nd row. This is how they will be filled and we can access any element with the help of two indexes that is row number and column number. Now, the other way of initializing it is,
int[,] A = new int[2,3]
{
       {2, 5, 9},{6, 9, 15}
};
Later part of this article, we will see how to initialize the 2D Array dynamically in C#. The following image shows the syntax of how we can initialize a 2D Rectangle Array in C#.

Next, let us see how to access the elements of the 2-D array.

Accessing the Elements of the 2D array in C#:

For accessing all the elements of the rectangle 2D Array in C#, we require a nested for loop, one for loop for accessing the rows, and another for loop for accessing the columns. So, by using a nested for loop we can access 2Dimensional Array Elements. For a better understanding, please have a look at the below image.

Example to Understand 2D Array in C#:

Let us see an example for a better understanding of the rectangular 2D array in C#. In the below example, we are creating a two-dimensional integer array with 4 Rows and 5 Columns. Then we are printing the values of the 2D Array using a for each loop to see what default it stores. Then using nested for loop, we are assigning the values to the 2D Array as well as Printing the values of the 2D Array. In the below example, we are using the Array class GetLength method, when we pass 0, it will return the size of the Rows and when we pass 1, it will return the size of the columns.

Output:

In the above example, we assigned the two-dimensional array elements using nested for loop. It is also possible that we can assign the values to a two-dimensional array in C# at the time of its declaration.

2D Array Declaration and Initialization at the Same Statement:

In the below example, we are assigning values to the two-dimensional array at the time of its declaration. Here, we do not need to specify the size as based on the argument values it will automatically choose the size. Here, it will create the array with the size of 3 Rows and 4 Columns. Then, we Printed the Array Elements using both ForEach Loop and Nested for Loop. In the nested for loop, the first for loop, loop variable i will point to the Rows, and in the second for loop, the loop variable I will point to the columns of the 2D Array.

Output:

Program to Add 2 Matrices using C#:

Output:

Jagged Array in C#:

These are also two-dimensional arrays that will also store the data in the forms of rows and columns. But here in the jagged array, the column size will differ from row to row. That means if the first row contains 5 columns, then the second row may contain 4 columns while the third row may contain 10 columns. So, the point that you need to remember is if the column size varies from row to row then it is a jagged array. If the column size remains the same for all the rows, then it is a rectangular two-dimensional array.

The jagged array in C# is also called the array of arrays. This is because in the case of the jagged array each row is a single-dimensional array. So, a combination of multiple single-dimensional arrays with different column sizes forms a jagged array in C#.

Syntax:  <type> [][] <name> = new <type> [rows][];
Example:
int [][] arr = new int[3][];
//Or
int [][] arr = {list of values};

To declare a jagged array in C#, at the time of its declaration, you only need to specify the number of rows that you want in the array. For example
int [][] arr = new int[4][];

In the above array declaration, we are specifying that we want four rows in the array. Once you specify the number of rows that you want in the array, then you need to initialize each row with the number of columns by using a single-dimensional array as shown below.
arr[0] = new int[5]; // we want five columns in the first row
arr[1] = new int[6]; // we want six columns in the first row
arr[2] = new int[4]; // we want four columns in the first row
arr[3] = new int[5]; // we want five columns in the first row

Example to Understand Jagged Array in C#:

Jagged Arrays in C# are nothing but the combination of multiple 1D Arrays. In the below example, we created one jagged array with 4 Rows and then we initialize each row of the Jagged Array with different 1-Dimensional Arrays. Then we print the default values of jagged array using the nested for loop and then we initialize the jagged array using the nested for loop. And finally, once we initialized the jagged array, then we print the elements of a jagged array using a for loop and for each loop.

Output:

In the next article, I am going to discuss the Advantages and Disadvantages of Arrays in C# with Examples. Here, in this article, I try to explain the 2D Arrays in C# with Examples. I hope this article will help you with your needs. I would like to have your feedback. Please post your feedback, question, or comments about this 2Dimensional Arrays in C# with Examples article.