CODEWITHSUNDEEP
c#
Mårten Cederholm
Mårten Cederholm

Reputation: 87

C# ArrayList - object

I have three classes in my C# program. Get the following error:

Cannot implicitly convert type 'object' to 'Register_Employee.Employee'. An explicit conversion exists (are you missing a cast?) C:\Users\x64\Documents\Visual Studio 2010\Projects\Register Employee\Register Employee\EmployeeList.cs 20 20 Register Employee

I know what the problem is. You have to return the correct type of object, but I don't know how to solve it. I have a class Employee, a class EmployeeList which holds employees and the main program.

namespace Register_Employee
{
    class EmployeeList
    {
        ArrayList list = new ArrayList();

       public void addEmployee(Employee a)
       {
           this.list.Add(a);
       }

        public Employee GetEmployee(int Index)
        {
            var e = list[Index]; <<<<<The problems
            return e;  <<<<<The problems
        }

    }
}

namespace Register_Employee
{
    class Employee
    {

        public Employee(String iD, String firstName, String lastName)
        {
            this.ID = iD;
            this.FirstName = firstName;
            this.LastName = lastName;
        }

        public String ID { get; set; }
        public String FirstName { get; set; }
        public String LastName { get; set; }


    }
}

Thanks in advance

Upvotes: 3

Views: 5501

Answers (7)

phoog
phoog

Reputation: 43046

The other answers here suggest or imply that you should use

List<Employee>

rather than ArrayList in your EmployeeList class. From your sample, it seems that EmployeeList is just a strongly-typed wrapper around ArrayList. If that's the case, you can get rid of EmployeeList entirely and use

List<Employee>

instead.

Upvotes: 1

Guillaume Slashy
Guillaume Slashy

Reputation: 3624

Just cast the object as an Employee Change this

var e = list[Index]; <<<<<The problems

To this 

var e = (Employee)list[Index]; <<<<<The problems

like a couple of guys said, you should definitely NOT use a generic Collection/List/IEnumerable

Upvotes: 1

Amar Palsapure
Amar Palsapure

Reputation: 9680

You will need to type cast object to Employee object

public Employee GetEmployee(int Index)
{
    var e = list[Index]; 
    return (Employee)e;  
}

.Net framework 2.0 or later has a generic class List which you can use instead of ArrayList. Represents a strongly typed list of objects that can be accessed by index. Check on MSDN.

In that case 

class EmployeeList
{
    List<Employee> list = new List<Employee>();
    //Rest of your code
}

Hope this helps you.

Upvotes: 3

rerun
rerun

Reputation: 25505

You can solve the problem in a couple of ways.

First if a thing is stored as an object but is actually a derived type you can always cast it to the appropriate type.

public Employee GetEmployee(int Index)
    {
        var e = list[Index]; 
        return (Employee)e; 
    }

However you loose type safety in doing so. A better solution is to use generics 

class EmployeeList
{
   List<Employee> list = new List<Employee>();

   public void addEmployee(Employee a)
   {
       this.list.Add(a);
   }

    public Employee GetEmployee(int Index)
    {
        var e = list[Index]; 
        return e;  //No cast needed 
    }

}

In this case you know have a list which supports type safety (ie you know everything in it is a Employee ) and will actually out perform the array list.

Upvotes: 3

Not-RocketScience
Not-RocketScience

Reputation: 162

Cast the object to the Employee object. Use List if you have the option.

Upvotes: 2

Henk Holterman
Henk Holterman

Reputation: 273244

Just use

public Employee GetEmployee(int Index)
{
  var e = list[Index];  // should work, e will be of type Object
  return (Employee) e; // <<<<<The problems
}

And consider using List<Employee> to have a more 'type-safe' collection. 

class EmployeeList
{
    //ArrayList list = new ArrayList();
    List<Employee> list = new List<Employee>();
    ...
}

Upvotes: 2

Strillo
Strillo

Reputation: 2972

As the error message says, you need to explicitly cast:

Employee e = (Employee)list[Index];

Also, you could use a List<Employee> instead of ArrayList.

Upvotes: 4

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