C#向数据库中插入或更新null空值与延迟加载lazy

int? item = null;
item == null ? 
"null"
 : item.ToString();
item == null ? "" : item.ToString();

int? item = null;
cmd.Parameters.Add(dbPams.MakeInParam(":Item", SqlNull(item)));
cmd.Parameters[0].IsNullable = true;//更新时需加入此句。

static public object SqlNull(object obj)
{
    return (item == null ? DBNull.Value : item)
}

static void Main(string[] args)
{
 Lazy lazyBig = new Lazy(); 
 Console.WriteLine("对象是否创建" + lazyBig.IsValueCreated);
 lazyBig.Value.Test(); 
 Console.WriteLine("对象是否创建" + lazyBig.IsValueCreated); 
} 

class Big {
 public Big() { } 
 public void Test() {
   Console.WriteLine("Test...."); 
}
 } //结果如下： //对象是否创建False //Test.... //对象是否创建True

static void Main(string[] args)
{
    Lazy lazyBig = new Lazy( () => new Big(100) );
    lazyBig.Value.Test();
} 

class Big { 
  public Big(int id) { this.ID = id; }
  public int ID { get; set; }
  public void Test()
    {
        Console.WriteLine("ID = " + ID.ToString());
    }
}