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Nirmal kumar
Nirmal kumar

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C# Indexers. When do we use it ?

#dotnet #csharp #dotnetcore #coding
C# Indexers:
  • C# indexers are like properties. It allows to access instances like an array with an index.
  • It always represents collection objects but exposes arguments using which we can use to identify a particular element in the collection at a time.
  • We can access an indexer by indexing the class instance with the appropriate index parameter.
  • We can overload indexers with different data types and create multiple indexers for a class to expose & access different collections using the same class instance.
  • It acts as a member of a class but is used to access a data item of a collection from outside the class.
When do we use it?
  • Let's say we have to load a collection object in memory and we don't know upfront exactly how much memory it would take. Indexers help to set up an approach to load a small chunk of the entire data load, process it, and then move on to the next chunk.
  • It helps to abstract collection type in the model from the usage class as it always allows to access one data item at a time. This helps code easier to understand and maintain.
  • Indexer should be used if providing an index to an object makes sense.
Simple Example: 
 public class Employee { public string Name{get;set;} public int Id {get;set;} public string Department{get;set;} public int DepartmentId{get;set;} public string City{get;set;} public string Zip{get;set;} } public enum DepartmentEnum{ None = 0, Engineering, Accounting, Economics, Politics } internal class Program { private static void Main(string[] args) { Console.WriteLine("Hello, World!"); var processor = new EmployeeProcessor(DepartmentEnum.Engineering); processor.ProcessPayroll(); processor.ProcessHealthInsurance(); Console.WriteLine($"Total engineering employees - {processor[DepartmentEnum.Engineering].Count()}"); Console.ReadKey(); } } public class EmployeeProcessor { private List<Employee> employees = new List<Employee>(); public EmployeeProcessor(DepartmentEnum department) { LoadEmployeesByDepartment(department); } public List<Employee> this[DepartmentEnum department] { get { return employees.Where(x=> x.DepartmentId == (int)department).ToList(); } } private void LoadEmployeesByDepartment(DepartmentEnum department) { //load it from the data source. I am Hard coding for a blog  if(department == DepartmentEnum.Engineering) { employees.Add( new Employee() { Name = "Nirmal kumar", Id = 1, Department = "Engineering", DepartmentId = 1, City = "Raleigh", Zip = "27616" }); } else if(department == DepartmentEnum.Accounting) { employees.Add(new Employee() { Name = "Preethi", Id = 1, Department = "Accounting", DepartmentId = 2, City = "Atlanta", Zip = "12345" }); } else if(department == DepartmentEnum.Economics) { employees.Add(new Employee() { Name = "Adithi", Id = 1, Department = "Economics", DepartmentId = 3, City = "New york", Zip = "23456" }); employees.Add(new Employee() { Name = "Pranavi", Id = 2, Department = "Economics", DepartmentId = 3, City = "New york", Zip = "23456" }); } } public void ProcessPayroll(){} public void ProcessHealthInsurance(){} }
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