Create Constructor for structure and use it with structure object c#

Question

    using System;
    using System.Collections.Generic;
    using System.Text;

    namespace ConsoleApp1
    {
    // I am using structure to define values type set 
        public struct Employee
        {
            public int EmpId;
            public string FirstName;
            public string LastName;

    // Here i am checking whether parameter less constructor will work 
            static Employee()
            {
                Console.WriteLine("First Object Created");
            }

// Here i am using one more constructor for initializing it with some values later on
            public void Employee(int number, string firsname, string lasname)
            {
                id = number;
                FirstName = firsname;
                LastName = lasname;
            }    
        }    

        // Here i am using the parameterize constructor to assign values mentioned before in the //structure

        class Program {

            Employee emp1 = new Employee(23,"shiva","shankar");            
        }      
    }

// Error i am getting is Employee structure doesnt contain constructor that takes 3 args // The name id doesnt exist in current context //Employee : member names cannot be same as their enclosing type

First off you're probably better off using a class, but if you do use a struct do not allow it to be mutable as that will allow you to modify a copy which does not modify the original. (better to not allow mutation and force uses of the struct to assign a new value) stackoverflow.com/questions/441309/why-are-mutable-structs-evil — juharr
– juharr, Commented Jan 26, 2020 at 16:26
FYI a general rule of thumb is that if the type contains reference types (like string) then it probably should be a reference type. — juharr
– juharr, Commented Jan 26, 2020 at 16:34

Nguyễn Văn Phong · Accepted Answer · 2020-01-26 16:27:16Z

2

the constructor doesn't have a return value.

public Employee(int number, string firsname, string lasname)

edited Jan 26, 2020 at 16:27

Nguyễn Văn Phong

14.2k19 gold badges47 silver badges65 bronze badges

answered Jan 26, 2020 at 16:20

Алексей О

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Comments

Pavel Anikhouski · Accepted Answer · 2020-01-29 12:12:24Z

There is no id field in your Employee struct, only EmpId. Also, constructor in C# can't have a return type:

A constructor is a method whose name is the same as the name of its type. Its method signature includes only the method name and its parameter list; it does not include a return type.

You should rewrite your code as following

// Here i am using one more constructor for initializing it with some values later on
public Employee(int number, string firstName, string lastName)
{
    EmpId = number;
    FirstName = firstName;
    LastName = lastName;
}

Also it makes sense to declare your fields as private, or use readonly properties instead, with getters only, initialized in constructor

public int EmpId { get; }
public string FirstName { get; }
public string LastName { get; }

Otherwise your struct is mutable. Also it contains a reference type values, like string. It's better to introduce an Employee class rather than struct

OO7 · Accepted Answer · 2020-01-27 22:11:33Z

Well, it seems it's need to define a new static member, then call that new one, so the static constructor will be triggered soon.

Let's to check this:

public static int id = 0;

static Employee()
{
    Console.WriteLine("First Object Created");
}

First call:

Emploee.id = 1;
Employee emp1 = new Employee(23,"shiva","shankar");

Console.WriteLine("Id: {0}", Employee.id);
Console.WriteLine("emp1.EmpId: {0}", emp1.EmpId);

Output:

First Object Created
Id: 1;
emp1.EmpId: 23

Second call:

Employee.id = 2;

// copy emp1 values to var emp2
var emp2 = emp1; // both emp1 and emp2 have same values

// set emp2.EmpId to new value.
emp2.EmpId = 24;

Console.WriteLine("Id: {0}", Employee.id);
Console.WriteLine("emp1.EmpId: {0}", emp1.EmpId);
Console.WriteLine("emp2.EmpId: {0}", emp2.EmpId);

Output:

Id: 2;
emp1.EmpId: 23
emp2.EmpId: 24

Hope this could helps. Cheers!

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