System.Object 学习笔记

1. System 命名空间包含基本类和基类，这些类定义常用的值和引用数据类型、事件和事件处理程序、接口、属性和异常处理。其他类提供的服务支持数据类型转换、方法参数操作、数学运算、远程和本地程序调用、应用程序环境管理和对托管与非托管应用程序的监控。
   
2.  GetHashCode() 方法：如果重写GetHashCode方法，需要考虑是否重写Equals方法， Equals方法主要是确保两个相等的对象必须拥有相同的HashCode。否则GetHashCode方法可能不能正常工作。如果使用了默认的GetHashCode()方法，.NET Framework将调用CLR中已经实现的方法来生成HashCode。 以下是Object类中实现GetHashCode的代码：

                // GetHashCode is intended to serve as a hash function for this object.
                // Based on the contents of the object, the hash function will return a suitable
                // value with a relatively random distribution over the various inputs.
                //
                // The default implementation returns the sync block index for this instance.
                // Calling it on the same object multiple times will return the same value, so
                // it will technically meet the needs of a hash function, but it's less than ideal.
                // Objects (& especially value classes) should override this method.
                //
               /// <include file='doc/Object.uex' path='docs/do[@for="Object.GetHashCode"]/*' />
                [MethodImplAttribute(MethodImplOptions.InternalCall)]
                public extern virtual int GetHashCode();

        2.    toString()方法，如果是Object对象调用了toString()方法。而类中又没有对toString方法进行重载，  那 么将返回这个类的类型。

                      // Returns a String which represents the object instance.  The default
                 // for an object is to return the fully qualified name of the class.
                 //
                /// <include file='doc/Object.uex' path='docs/doc[@for="Object.ToString"]/*' />
                 public virtual String ToString()
                 {
                       return GetType().FullName;
                 }