Implimenting Is Functionality in c#

Hemalatha Sunnapu

7y860Learn iOS Programming

Can we do IS functionality without using Is keyword as well as GetType and typeof functions.

Here i am specific about the heirarchy need to be given by the Is functionality

13 Replies

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Hemalatha Sunnapu7y ago
Thank you jaish
Jaish Mathews7y ago
OK. Below are the standards to use in your scenario.
Always use "is" operator whenever comparing types/class. Because == operator will fail for derived classes and many other scenarios
Never ever use string conversion and string comaprison for comparing types.
Your expected types comparison can be achieved by merely using "is"
Below is your modified code and I see the expected results too as per your code comments. Identify the commented and added code sections. You don't need a custom "is" implementation.
static void Main(string[] args)
{
Student studentObject = new Student();
Employee employeObject = new Employee();
Teacher teacherObject = new Teacher();
////String teacherValue = Convert.ToString(teacherObject);
////String studentValue = Convert.ToString(studentObject);
////String employeValue = Convert.ToString(employeObject);

// Is operator
Console.WriteLine(" Is Functionality \n");
// Check Employee employeObject is Student Type
// bool isStudent = (employeValue == studentValue);
bool isStudent = employeObject is Student;

Console.WriteLine("employeObject is a Student type : {0}", isStudent + "\n");

// Check studentObjectj is Student Type
//isStudent = (studentValue == studentValue);
isStudent = studentObject is Student;

Console.WriteLine("studentObject is a Student type : {0}", isStudent + "\n");

// Check teacherObject is Student Type
//isStudent = (teacherValue == studentValue);
isStudent = teacherObject is Student;

Console.WriteLine("teacherObject is a Student type : {0}", isStudent + "\n");

// Check null object Type
studentObject = null;
//string value1 = Convert.ToString(studentObject);
// isStudent = (studentValue == value1);
isStudent = studentObject is Student;

Console.WriteLine("studentObject(null) is a Student type : {0}", isStudent + "\n");

Console.Read(); ;
}

class Student
{
//public override string ToString()
//{ return "Student"; }
}
class Teacher
{

}

class Employee : Student
{

}
Hemalatha Sunnapu7y ago
Hello All,
Here is my code..
using System;
namespace IsAndAsFunctionality
   { class Student
    {
      public override string ToString()
         { return "Student"; }
    }
   class Teacher { }
    class Employee : Student
    {
         static void Main(string[] args)
          {
                Student studentObject = new Student();
                Employee employeObject = new Employee();
                Teacher teacherObject = new Teacher();
               String teacherValue = Convert.ToString(teacherObject);
                String studentValue = Convert.ToString(studentObject);
                String employeValue = Convert.ToString(employeObject);
// Is operator
                   Console.WriteLine(" Is Functionality \n");
       // Check Employee employeObject is Student Type
           bool isStudent = (employeValue == studentValue);
                   Console.WriteLine("employeObject is a Student type : {0}", isStudent+"\n");
// Check studentObjectj is Student Type
   isStudent = (studentValue == studentValue);
   Console.WriteLine("studentObject is a Student type : {0}", isStudent + "\n");
// Check teacherObject is Student Type
          isStudent = (teacherValue == studentValue);
          Console.WriteLine("teacherObject is a Student type : {0}", isStudent + "\n");
// Check null object Type
          studentObject = null; string value1 = Convert.ToString(studentObject);
          isStudent = (studentValue == value1);
          Console.WriteLine("studentObject(null) is a Student type : {0}", isStudent + "\n");
       Console.Read();
      }
   }
}
Jaish Mathews7y ago
Ref. to your code, "==" and "is" won't give same results for all cases. So this is not a problem, but expected bahaviour.

Probably so far not getting what you need, especially what is compelling you to not use built-in functionality and write the same by your own.
Sreekanth Reddy7y ago
Can you please provide your isStudent() method related coding part ?
Hemalatha Sunnapu7y ago
Hi sreekanth,
I ahve implemented Is functionality ,everything is fine but the onlu probelm is :
In inhertinace
Example :
bool isStudent (Empobj is Student);//returns true as employe id derived                                                         // from student
isStudent (stuobj is Employe); //retuns false
/* IN MY CODE*/
bool isStudent (Empobj ==Student);//returns true as employe id derived
                                                          // from student
isStudent (stuobj is Employe); //retuning true(this is probelm)


I have wrote function (logic)to get that.Can anyone help me out.
Sreekanth Reddy7y ago
The thing that what I can speak is: Just imagine "is" also behaving as a logical operator "==".
Behaves as same I feel.
For Ex :

if we try as like below :
if("abc"=="def") // Correct doesnt throw error.
if("abc"==123) // Throws error.

Just think how it's possible ?
This logic has already written by microsoft and simply provided us operator (==) to compare.
In the same way the "is" too working I hope.
Hemalatha Sunnapu7y ago
Hello Jaish ,
Thanks for your response , i just wanted to do Is functionality with a logic instead of Is Keyword
Hemalatha Sunnapu7y ago
Yes, i have tried this and even i got the answer, i want to do without built in functions
Hemalatha Sunnapu7y ago
Yes, i have tried this and even i got the answer, i want to do without built in functions
Sreekanth Reddy7y ago
Generally "is" keyword is used to compare the objects.
So, I'm not sure.. But try with equilizing the objects(Ex: GetType(obj1) == GetType(obj2)).
Hemalatha Sunnapu7y ago
Yes i knew that, but what Iam trying to know is the "logic" of that keyword
Sreekanth Reddy7y ago
As "is" is a keyword, The internal functionality is going to handled by the CLR.
We cant even find the "Go to definition" too.