IsFixedSize, IsReadOnly

The Array type provides several properties. Some of these help us detect features. These include IsFixedSize, IsReadOnly and IsSynchronized.

Property notes

These properties are defined on the IList and ICollection interfaces. IList requires IsFixedSize and IsReadOnly, and ICollection requires IsSynchronized.

In this code example, we see 3 parts. First we see the C# program that uses the 3 properties. Next we see the output of the program, and the property implementations.

using System;

class Program
{
    static void Main()
    {
        int[] array = new int[4];
        Console.WriteLine(array.IsFixedSize);
        Console.WriteLine(array.IsReadOnly);
        Console.WriteLine(array.IsSynchronized);
    }
}
True
False
False
public bool IsFixedSize
{
    get
    {
        return true;
    }
}

public bool IsReadOnly
{
    get
    {
        return false;
    }
}

public bool IsSynchronized
{
    get
    {
        return false;
    }
}

IList, ICollection

If you have a variable reference of type IList or ICollection, these properties may be useful. These properties help with the interfaces an array implements.

A summary

We looked at the IsFixedSize, IsReadOnly, and IsSynchronized properties. If you know you are dealing with an array, these properties are never useful—they are constant.