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  • Conversion Operators in Linq

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    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:-

     

     

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