Public Class ClassWithIndexer
    Private x As Integer()
    Public Default Property Item(ByVal index As Integer) As Integer
        Get
            Return x(index)
        End Get
        Set
            x(index) = Value
        End Set
    End Property
End Class

The above VB code is the equivalent for the following C# code:
public class ClassWithIndexer
{
    private int[] x;
    public int this[int index]
    {
        get
        {
            return x[index];
        }
        set
        {
            x[index] = value;
        }
    }
}