Adapter Design Pattern C# with Example

“Adapter” as the name suggests is the object which lets two mutually incompatible interfaces communicate 
with each other. 
For example: if you buy a Iphone 8 (or any other Apple product) you need alot of adapters. Because the 
default interface does not support audio jac or USB. With these adapters you can use earphones with 
wires or you can use a normal Ethernet cable. So "two mutually incompatible interfaces communicate with 
each other". 
So in technical terms this means: Convert the interface of a class into another interface that a clients 
expect. Adapter let classes work together that couldn't otherwise because of incompatible interfaces. The 
classes and objects participating in this pattern are: 
The adapter pattern exits out 4 elements 
1. ITarget: This is the interface which is used by the client to achieve functionality. 
2. Adaptee: This is the functionality which the client desires but its interface is not compatible with 
the client. 
3. Client: This is the class which wants to achieve some functionality by using the adaptee ’s code. 
4. Adapter: This is the class which would implement ITarget and would call the Adaptee code which 
the client wants to call. 
UML 
First code Example (Theoretical example). 
 

public interface ITarget 
{ 
void MethodA(); 
} 
public class Adaptee 
{ 
public void MethodB() 
{ 
Console.WriteLine("MethodB() is called"); 
} 
} 
public class Client 
{ 
private ITarget target; 
public Client(ITarget target) 
{ 
this.target = target; 
} 
public void MakeRequest() 
{ 
target.MethodA(); 
} 
} 
public class Adapter : Adaptee, ITarget 
{ 
public void MethodA() 
{ 
MethodB(); 
} 
} 
Second code example (Real world imlementation) 
/// 
 
/// Interface: This is the interface which is used by the client to achieve functionality. 
/// 
 
public interface ITarget 
{ 
List GetEmployeeList(); 
} 
/// 
 
/// Adaptee: This is the functionality which the client desires but its interface is not compatible 
with the client. 
/// 
 
public class CompanyEmplyees 
{ 
public string[][] GetEmployees() 
{ 
string[][] employees = new string[4][]; 
employees[0] = new string[] { "100", "Deepak", "Team Leader" }; 
employees[1] = new string[] { "101", "Rohit", "Developer" }; 
employees[2] = new string[] { "102", "Gautam", "Developer" }; 
employees[3] = new string[] { "103", "Dev", "Tester" }; 
 

return employees; 
} 
} 
/// 
 
/// Client: This is the class which wants to achieve some functionality by using the adaptee’s code 
(list of employees). 
/// 
 
public class ThirdPartyBillingSystem 
{ 
/* 
* This class is from a thirt party and you do'n have any control over it. 
* But it requires a Emplyee list to do its work 
*/ 
private ITarget employeeSource; 
public ThirdPartyBillingSystem(ITarget employeeSource) 
{ 
 

this.employeeSource = employeeSource; 
} 
 

public void ShowEmployeeList() 
 

{ 
 

// call the clietn list in the interface 
 

List employee = employeeSource.GetEmployeeList(); 
 

Console.WriteLine("######### Employee List ##########"); 
 

foreach (var item in employee) 
 

{ 
Console.Write(item); 
 

} 
} 
 

} 
 

/// 
 

/// Adapter: This is the class which would implement ITarget and would call the Adaptee code which 

the client wants to call. 

/// 
 

public class EmployeeAdapter : CompanyEmplyees, ITarget 

{ 

public List GetEmployeeList() 

{ 

List employeeList = new List(); 
string[][] employees = GetEmployees(); 
foreach (string[] employee in employees) 
 

{ 
 

employeeList.Add(employee[0]); 

employeeList.Add(","); 

employeeList.Add(employee[1]); 

employeeList.Add(","); 

employeeList.Add(employee[2]); 

employeeList.Add("\n"); 

} 

return employeeList; 
} 
} 
/// 
/// Demo 
 

/// 
class Programs 
{ 
static void Main(string[] args) 
{ 
ITarget Itarget = new EmployeeAdapter(); 
ThirdPartyBillingSystem client = new ThirdPartyBillingSystem(Itarget); 
client.ShowEmployeeList(); 
Console.ReadKey(); 
} 
} 
When to use 
Allow a system to use classes of another system that is incompatible with it. 
Allow communication between new and already existing system which are independent to each other 
Ado.Net SqlAdapter, OracleAdapter, MySqlAdapter are best example of Adapter Pattern.