Program.cs

[DebuggerDisplay("Age {Age > 0 ? Age : 5}")]
public class DebuggerDisplayTest
{
    private string squirrelFirstNameName;
    private string squirrelLastNameName;

    public string SquirrelFirstNameName 
    {
        get
        {
            return squirrelFirstNameName;
        }
        set
        {
            squirrelFirstNameName = value;
        }
    }

    [DebuggerBrowsable(DebuggerBrowsableState.Collapsed)]
    public string SquirrelLastNameName
    {
        get
        {
            return squirrelLastNameName;
        }
        set
        {
            squirrelLastNameName = value;
        }
    }

    public int Age { get; set; }

    private string DebuggerDisplay
    {
        get { return string.Format("{0} de {1}", SquirrelFirstNameName, SquirrelLastNameName); }
    }
}