[英]How to check equality of boxed object of value types when types are different but compatible to compare the values
When we box two value types(which are different types but compatible to compare the values eg: int and short) and try to call Equals method on that gives false even the values are same. 当我们将两个值类型(它们是不同类型但可以比较以比较值,例如:int和short)装箱并尝试调用Equals方法时,即使值相同,也会给出false。
Case 1: 情况1:
int a = 5;
short b = 5;
var ob_a = (object) a;
var ob_b = (object) b;
var result = a == b; // true
var result_for_objects = ob_a.Equals(ob_b); // false
On the other hand when the both value types are same the Equals returns the actual value comparison result. 另一方面,当两个值类型相同时,Equals返回实际值比较结果。
Case 2: 情况2:
int a = 5;
int b = 5;
var ob_a = (object) a;
var ob_b = (object) b;
var result = a == b; // true
var result_for_objects = ob_a.Equals(ob_b); // true
I compared the both disassembly code for of both case but it was same, I was not able to find any difference. 我比较了这两种情况的两种反汇编代码,但都一样,我找不到任何区别。
var result = a == b;
012404DE mov eax,dword ptr [ebp-40h]
012404E1 cmp eax,dword ptr [ebp-44h]
012404E4 sete al
012404E7 movzx eax,al
012404EA mov dword ptr [ebp-50h],eax
var result_for_objects = ob_a.Equals(ob_b);
012404ED mov ecx,dword ptr [ebp-48h]
012404F0 mov edx,dword ptr [ebp-4Ch]
012404F3 mov eax,dword ptr [ecx]
012404F5 mov eax,dword ptr [eax+28h]
012404F8 call dword ptr [eax+4]
012404FB mov dword ptr [ebp-5Ch],eax
012404FE movzx eax,byte ptr [ebp-5Ch]
01240502 mov dword ptr [ebp-54h],eax
The type of the variable is kept in object. 变量的类型保留在对象中。
For example: 例如:
Console.Write(ob_a.GetType().ToString()); // will give you System.Int32
Console.Write(ob_b.GetType().ToString()); // will give you System.Int16
It gives different hash codes also with method: GetHashCode()
它也使用方法提供不同的哈希码:
GetHashCode()
If you will convert short variable to int or the other way, it will be equal... So basically the problem is with different variable types. 如果将short变量转换为int或以其他方式转换,则将是相等的...因此,基本上,问题出在不同的变量类型上。
Here is the answer for both questions: http://www.ikriv.com/dev/dotnet/ObjectEquality.html 这是两个问题的答案: http : //www.ikriv.com/dev/dotnet/ObjectEquality.html
Since call to Equals() is virtual, exact version of the method that will be called by x.Equals(y) is determined by dynamic type of x, that usually is not known at compile time.
由于对Equals()的调用是虚拟的,因此将由x.Equals(y)调用的方法的确切版本由x的动态类型确定,通常在编译时未知。 Note also, that unlike a==b, expression x.Equals(y) is inherently asymmetrical.
还要注意,与a == b不同,表达式x.Equals(y)本质上是不对称的。 Only x dictates what version of Equals() will be called.
只有x指示将调用哪个版本的Equals()。 y has absolutely no say in the matter.
您对此事绝对没有发言权。
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