Conversion Operators are helpful in transforming the type of the item in a collection.

In linq, We have a three types of conversion operators:-

1. As operators(AsEnumerable and AsQueryable)

2. To operators(ToArray, ToDictionary, ToList and ToLookUp)

3. Casting operators(Cast and OfType)

1. As operators(AsEnumerable and AsQueryable)

These AsEnumerable and AsQueryable methods transform a input data to IEnumerable<T> or IQueryable<T>.

Example:-

class SampleProgram
{
    static void ReportProperties<T>(T obj)
    {
        Console.WriteLine("Compile-time type: {0}", typeof(T).Name);
        Console.WriteLine("Actual type: {0}", obj.GetType().Name);
    }
    static void Main(string[] args)
    {
        Employee[] empArray = { 
        new Employee() { EmpID = Guid.NewGuid().ToString(), EmpName = "John", Age = 18 } ,
        new Employee() { EmpID = Guid.NewGuid().ToString(),  EmpName = "Stefen",  Age = 21 } ,
        new Employee() { EmpID = Guid.NewGuid().ToString(),  EmpName = "Bill",  Age = 25 } ,
        new Employee() { EmpID = Guid.NewGuid().ToString(),  EmpName = "Rami" , Age = 20 } ,
        new Employee() { EmpID = Guid.NewGuid().ToString(),  EmpName = "Rohan" , Age = 31 } 
            };   
        ReportProperties( empArray );
        ReportProperties(empArray.AsEnumerable());
        ReportProperties(empArray.AsQueryable());   
    }
}      

Output:-

2. To Operators(ToArray(), ToList(), ToDictionary())

These operators cast the input data to their corresponding type such as an Array, List or Dictionary respectively.

Example:-

Code:-

IList<int> numberList = new List<int>() { 1, 2, 30 ,14, 17};
int[] numArray = numberList.ToArray<int>(); 
IList<int> numList = numArray.ToList<int>(); 
Console.WriteLine("ToArray :-");
foreach(var num in numberList )
{
  Console.WriteLine(num);
}
  Console.WriteLine();
Console.WriteLine("ToList :-");
foreach(var num in numList)
{
  Console.WriteLine(num);
}

Output:-

ToDictionary:- It is converts a generic list to a generic dictionary

Example:-

Code:-

IList<Employee> empList = new List<Employee>() { 
        new Employee() { EmpID = Guid.NewGuid().ToString(), EmpName = "John", Age = 18 } ,
        new Employee() { EmpID = Guid.NewGuid().ToString(),  EmpName = "Stefen",  Age = 21 } ,
        new Employee() { EmpID = Guid.NewGuid().ToString(),  EmpName = "Bill",  Age = 25 } ,
        new Employee() { EmpID = Guid.NewGuid().ToString(),  EmpName = "Rami" , Age = 20 } ,
        new Employee() { EmpID = Guid.NewGuid().ToString(),  EmpName = "Rohan" , Age = 31 } 
    };

IDictionary<int, Employee> empDict = 
                                empList.ToDictionary<Employee, int>(e => e.EmpID); 

foreach(var key in empDict.Keys)
	Console.WriteLine("Key: {0}, Value: {1}", 
                                key, (empDict[key] as Employee).EmpName);

Output:-

3. Casting operators(Cast and OfType)

Cast:- Cast operator is used to convert a non-generic collection to a generic collection i.e. it convert a input data collection to the IEnumerable<T>.

Example:-

Code:-

class Program
{
    static void ReportProperties<T>(T obj)
    {
        Console.WriteLine("Compile-time type: {0}", typeof(T).Name);
        Console.WriteLine("Actual type: {0}", obj.GetType().Name);
    }

    static void Main(string[] args)
    {
       Employee[] empArray = {
        new Employee() { EmpID = Guid.NewGuid().ToString(), EmpName = "John", Age = 18 } ,
        new Employee() { EmpID = Guid.NewGuid().ToString(),  EmpName = "Stefen",  Age = 21 } ,
        new Employee() { EmpID = Guid.NewGuid().ToString(),  EmpName = "Bill",  Age = 25 } ,
        new Employee() { EmpID = Guid.NewGuid().ToString(),  EmpName = "Rami" , Age = 20 } ,
        new Employee() { EmpID = Guid.NewGuid().ToString(),  EmpName = "Rohan" , Age = 31 } 
    };
        ReportProperties( empArray );
        ReportProperties(empArray.Cast<Employee>());
    }
}      

Output:-

OfType:- It is used to filters a collection based on a specified type

Example:-

Code:-

IList list = new ArrayList();
            list.Add(0);
            list.Add("Zero");
            list.Add(new Employee() { EmpID = Guid.NewGuid().ToString(), EmpName = "Stefen", Age = 21 });
            var intResult = from l in list.OfType<string>() select l;
            foreach(var item in intResult)
            {
                Console.WriteLine(item);
            }

Output:-