Constant vs Readonly

-

Difference between a Constant and Readonly?

Both constant and readonly belong to the category of constant values with only major difference that one is a compile time constant and other is a runtime constant.

Compile time constant

"Constant" is a compile time constant type i.e. when you declare it you have to assign it a value otherwise you will not be able to compile your program.

In the following screen shot you will notice that readonly field is alright even if you do not assign it a value but constant field requires a value otherwise you will not be able to compile your program.


Run time constant

"Readonly" is a run time constant type i.e. when you declare it you do not have to assign it a value but you can only assign it a value inside the class constructor otherwise you will get a compile time error. If you want to define it on compile time that is totally alright as well.




So in order to properly define it look at the image below:

Remember once it is defined in the constructor you can not change it anywhere else.

Conclusion

  • 1# - Constant and Readonly fields are very frequently used in the programming but how they are used really makes a difference. End result for both of them is the same once value is set you can not change it. However; readonly fields have an exception case you can change the readonly value define at the class level inside the constructor. we will see this in a snapshot shortly.
  • 2# - Constant must have a value defined at the compile time you will not be able to assign it a value later; not even in the constructor or any other place. we will see this in a snapshot shortly.
  • 3# - Readonly can either be defined at compile time or runtime but will only accept a value inside the constructor if not defined during compile time. Once defined you can not change the value outside the constructor.
  • 4# - public constants defined in a class can not be accessed out side the class using a instance of the class. However you should be able to access them using the class name directly. we will see this in a snapshot shortly.



Properly defined program with all conditions satisfied will look like:


Comments

Post a Comment

Popular posts from this blog

Azure - Manage Blob Storage - Part #7 - Add Metadata to an Existing Container using C#

-
Image
Problem Definition How to add Metadata to and Existing container using C# in Azure. Prerequisites Access to Azure Portal -  http://portal.azure.com Azure General Purpose Storage Account Microsoft Visual Studio(For this demo used Visual Studio Community for Mac) Storage Account connection string as described in  Part #1 Complete Visual studio connectivity to Azure as described in  Part #1 Create a blob container as described in in  Part #2 Use following code to set up a new method in your class "BlobStorageContainer.cs" CloudBlobContainer will use the name that was passed to check if container exists or not. For block blob to be created container should be existing refer to  Part #2  to see how to create the container. How to call from "Program.cs" Results Program execution Azure confirmation Resources https://docs.microsoft.com/en-us/azure/storage/blobs/storage-quickstart-bl...
Read more

Azure - Manage Blob Storage - Part #5 - Create Folder Structure and upload a file to folder using an Existing Container using C#

-
Image
Problem Definition How to create directory structure and files using C# in Azure. Prerequisites Access to Azure Portal -  http://portal.azure.com Azure General Purpose Storage Account Microsoft Visual Studio(For this demo used Visual Studio Community for Mac) Storage Account connection string as described in  Part #1 Complete Visual studio connectivity to Azure as described in  Part #1 Create a blob container as described in in  Part #2 Use following code to set up a new method in your class "BlobStorageContainer.cs" CloudBlobContainer will use the name that was passed to check if container exists or not. For block blob to be created container should be existing refer to  Part #2  to see how to create the container. How to call from "Program.cs" Results Program execution Azure confirmation Resources https://docs.microsoft.com/en-us/azure/storage/blobs/storage-quickstart-blobs-dotn...
Read more

Algorithm - Breadth First Search(BFS) - Python(3)

-
Problem Definition Understand and implement BFS in Python Breadth-first search (BFS) is an algorithm for traversing or searching tree or graph data structures. It starts at the tree root (or some arbitrary node of a graph, sometimes referred to as a 'search key'[1]), and explores all of the neighbor nodes at the present depth prior to moving on to the nodes at the next depth level. Python Code graph = {   '1' : ['2','3'],   '2' : ['4', '5'],   '3' : ['6'],   '4' : ['7'],   '5' : ['6'],   '6' : [],   '7' : ['8'],   '8' : [] } queued_nodes = []   visited_nodes = []  def bfs(visited_nodes, graph, node):   print ("Following represent graph traverse for node: " + node)   visited_nodes.append(node)   queued_nodes.append(node)     while queued_nodes:     q = queued_nodes.pop(0)      print (q, end = " ")      for neighbour_node in graph[q]:...
Read more