Understanding Chain of Responsibility Pattern in C#

According to Gang of Four, it defines a chain of responsibilities to process a request. In other words, pass the request from one object to another until an object accepts its responsibility. Use Case Let’s consider an example of a claims system in any corporate company. Here is the list of the price range that can be approved and by whom. 100–1000 Rs => Junior/Senior Engineers => Approved by Manager 1001–10000 Rs => Managers => Approved by Senior Manager If the amount is outside the 10000 range, it requires exceptional approval from the senior manager. Implement the above use case using the Chain of Responsibility design pattern. So, the claim class has the following properties. { Id{ ; ;} amount{ ; ;} } public class Claim public int get set public double get set Prerequisites Basic knowledge of OOPS concepts.Any programming language knowledge. The article demonstrates the usage of Chain of Responsibility design patterns using the C# programming language. So, to begin with, C# C# has been around for quite some period, and it continues to develop, obtaining more enhanced features. Getting Started Firstly, let's define what functions a claim approver can perform and set a hierarchy for employees at different levels. Implement an abstract class as shown below { ClaimApprover claimApprover; { .claimApprover = claimApprover; } ; } public abstract class ClaimApprover protected ( ) public void SetHierarchy ClaimApprover claimApprover this ( ) public abstract void ApproveRequest Claim claim As per the use case, let’s drive class “junior/senior” claim requestor. Notice that this class/designation of employees cannot approve any claims. : { ApproveRequest(Claim claim) { System.Console.WriteLine( ); } } public class Junior ClaimApprover public override void "Cannot approve" Similarly, let’s define implement for Manager and Senior Manager roles. : { ApproveRequest(Claim claim) { (claim.amount >= && claim.amount <= ) { System.Console.WriteLine($ ); } (claimApprover != ) { claimApprover.ApproveRequest(claim); } } } public class Manager ClaimApprover public override void if 100 1000 "Claim reference {claim.Id} with amount {claim.amount} is approved by Manager" else if null Notice that based upon amount range, if within the range, the claim should be approved by the Manager; otherwise, the request will carry forward onto the Senior Manager. : { { (claim.amount > && claim.amount <= ) { System.Console.WriteLine( ); } { System.Console.WriteLine( ); } } } public class SeniorManager ClaimApprover ( ) public override void ApproveRequest Claim claim if 1000 10000 $"Claim reference with amount is approved by Senior Manager" {claim.Id} {claim.amount} else $"Exceptional approval for Claim reference with amount is approved by Senior Manager" {claim.Id} {claim.amount} Similarly, if the amount range is within the Senior Manager range, the claim can be approved by the Manager; otherwise, being last in the hierarchy, an exceptional approval is done for an amount outside the range. How to use the Chain of Responsibility pattern? ClaimApprover junior = ; ClaimApprover sukhpinder = ; ClaimApprover singh = ; junior. ; sukhpinder. ; Claim c1 = { amount = , Id = }; Claim c2 = { amount = , Id = }; junior. ; sukhpinder. ; new Manager() new Manager() new SeniorManager() SetHierarchy( ) sukhpinder SetHierarchy( ) singh new Claim() 999 1001 new Claim() 10001 1002 ApproveRequest( ) c1 ApproveRequest( ) c2 Define claim approver: junior, although it cannot approve any claims. Define claim approver: manager “sukhpinder.” Define claim approver: senior manager “singh.” Setup hierarchy relationship for junior, i.e., claims approver is the manager. Setup hierarchy relationship for the manager, i.e., claims approver is the senior manager. Create two different ranges of claims. Junior sends the claim request to the manager. The manager sends the claim request to the senior manager. Output Claim reference 1001 with amount 999 is approved by Manager Exceptional approval for Claim reference 1002 with amount 10001 is approved by Senior Manager For line 1 output, the amount was within the range, so the manager approved it. For line 2 output, although the senior manager approves it, the amount was outside the range. Github Repo The following repository shows the above use case implementation using a Chain of Responsibility Design Pattern in the console-based application. => Sample Code Thank you for reading, and I hope you liked the article. Read behind a paywall at https://medium.com/c-sharp-progarmming/how-to-use-chain-of-responsibility-pattern-f0f4896efc74