Generics and LINQ

Generics is a feature that is very useful in ASP.NET. If generic collection is used to store data then quering data from the collection becomes really easy.

Given below is a simple example for creating a generic collection and quering from it using LINQ.

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1) Create an object collection
a) Define the object "Employee"

public class Employee
{
public Employee(int iID, string strName, string strAddress, int iAge)
{
ID = iID;
Name = strName;
Address = strAddress;
Age = iAge;
}
public int ID { get; set; }
public string Name { get; set; }
public string Address { get; set; }
public int Age { get; set; }
}

b)Add objects to collection

public List GetEmployees()
{

List<Employee> lstEmps = new List<Employee>();

lstEmps.Add(new Employee(1, "Emp 1", "212 Street1", 34));
lstEmps.Add(new Employee(2, "Emp 2", "543 Street2", 31));
lstEmps.Add(new Employee(3, "Emp 3", "3332 Street2", 27));
lstEmps.Add(new Employee(4, "Emp 4", "1011 Street2", 40));
lstEmps.Add(new Employee(5, "Emp 5", "3214 Street4", 33));
lstEmps.Add(new Employee(6, "Emp 6", "5543 Street1", 35));

return lstEmps;
}

2) Query collection using LINQ

List<employee> EmpList =GetEmployees();

/**LINQ Examples**/

//Select employees with age > 30
List<employee> emps1 = (from x in EmpList where x.Age > 30 select x).ToList();

//Select employees with name starting with "Emp"
List<employee> emps2 = (from x in EmpList where x.Name.StartsWith("Emp") select x).ToList();

//Select employee with address "212 Street1"
List<employee> emps3 = (from x in EmpList where x.Address == "212 Street1" select x).ToList();