C#ValueType实现

源码

ValueType是Class,重要的重写了Object.Equals方法,导致值类型行为与引用类型的不同比较行为

// ==++==
// 
//   Copyright (c) Microsoft Corporation.  All rights reserved.
// 
// ==--==
/*============================================================
**
** Class:   ValueType
**
**
** Purpose: Base class for all value classes.
**
**
===========================================================*/
namespace System {
    using System;
    using System.Reflection;
    using System.Runtime.CompilerServices;
    using System.Runtime.Versioning;
 
    [Serializable]
[System.Runtime.InteropServices.ComVisible(true)]
    public abstract class ValueType {
 
        [System.Security.SecuritySafeCritical]
        public override bool Equals (Object obj) {
            BCLDebug.Perf(false, "ValueType::Equals is not fast.  "+this.GetType().FullName+" should override Equals(Object)");
            if (null==obj) {
                return false;
            }
            RuntimeType thisType = (RuntimeType)this.GetType();
            RuntimeType thatType = (RuntimeType)obj.GetType();
 
            if (thatType!=thisType) {
                return false;
            }
 
            Object thisObj = (Object)this;
            Object thisResult, thatResult;
 
            // if there are no GC references in this object we can avoid reflection 
            // and do a fast memcmp
            if (CanCompareBits(this))
                return FastEqualsCheck(thisObj, obj);
 
            FieldInfo[] thisFields = thisType.GetFields(BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic);
 
            for (int i=0; i<thisFields.Length; i++) {
                thisResult = ((RtFieldInfo)thisFields[i]).UnsafeGetValue(thisObj);
                thatResult = ((RtFieldInfo)thisFields[i]).UnsafeGetValue(obj);
                
                if (thisResult == null) {
                    if (thatResult != null)
                        return false;
                }
                else
                if (!thisResult.Equals(thatResult)) {
                    return false;
                }
            }
 
            return true;
        }
    }
}