Interface Properties
Properties can be declared on interfaces. The declaration takes the following form:
[attributes] [new] type identifier {interface-accessors}
where:
- attributes (Optional)
- Same as properties on classes.
- type
- Same as properties on classes.
- identifier
- The property name.
- interface-accessors
- The property accessors. See the Remarks section below.
Remarks
The accessor of an interface property does not have a body.
Thus, the purpose of the accessors is to indicate whether the property is read-write, read-only, or write-only.
The following is an example of an interface indexer accessor:
public interface IMyInterface
{
// Property declaration:
string Name
{
get;
set;
}
}
Example
In this example, the interface IEmployee has a read-write property, Name, and a read-only property, Counter. The class Employee implements the IEmployee interface and uses these two properties. The program reads the name of a new employee and the current number of employees and displays the employee name and the computed employee number.
// cs_interface_properties.cs
// Interface Properties
using System;
interface IEmployee
{
string Name
{
get;
set;
}
int Counter
{
get;
}
}
public class Employee: IEmployee
{
public static int numberOfEmployees;
private int counter;
private string name;
// Read-write instance property:
public string Name
{
get
{
return name;
}
set
{
name = value;
}
}
// Read-only instance property:
public int Counter
{
get
{
return counter;
}
}
// Constructor:
public Employee()
{
counter = ++counter + numberOfEmployees;
}
}
public class MainClass
{
public static void Main()
{
Console.Write("Enter number of employees: ");
string s = Console.ReadLine();
Employee.numberOfEmployees = int.Parse(s);
Employee e1 = new Employee();
Console.Write("Enter the name of the new employee: ");
e1.Name = Console.ReadLine();
Console.WriteLine("The employee information:");
Console.WriteLine("Employee number: {0}", e1.Counter);
Console.WriteLine("Employee name: {0}", e1.Name);
}
}
Input
210 Hazem Abolrous
Sample Output
Enter number of employees: 201 Enter the name of the new employee: Hazem Abolrous The employee information: Employee number: 202 Employee name: Hazem Abolrous
In the preceding example, you could use the fully qualified name of the property, which references the interface in which the member is declared. For example:
public string IEmployee.Name
{
}
However, the fully qualified name is only needed to avoid ambiguity when the class is implementing more than one interface with the same property signature. For example, if the class Employee is implementing two interfaces ICitizen and IEmployee and both interfaces have the Name property, the explicit interface member implementation will be necessary. That is, the following property declaration:
public string IEmployee.Name
{
}
implements the Name property on the IEmployee interface, while the following declaration:
public string ICitizen.Name
{
}
implements the Name property on the ICitizen interface.
For more information, see 13.4.1 Explicit interface member implementations.
See Also
Properties | Accessors | Comparison Between Properties and Indexers
