!(ReferenceEquals()) vs != in Entity Framework 4
Unless a class specifically overrides the behavior defined 开发者_运维知识库for Object, ReferenceEquals and == do the same thing... compare references.
In property setters, I have commonly used the pattern
private MyType myProperty;
public MyType MyProperty
{
set
{
if (myProperty != value)
{
myProperty = value;
// Do stuff like NotifyPropertyChanged
}
}
}
However, in code generated by Entity Framework, the if
statement is replaced by
if (!ReferenceEquals(myProperty, value))
Using ReferenceEquals is more explicit (as I guess not all C# programmers know that == does the same thing if not overridden).
Is there any difference that's escaping me between the two if-variants? Are they perhaps accounting for the possibility that POCO designers may have overridden ==
?
In short, if I have not overridden ==
, am I save using != instead of ReferenceEquals()
?
Here are the different semantics:
ReferenceEquals()
must be used if you mean that the objects are exactly the same (identity check).object.Equals()
shall be used if you mean the objects have the same value (equality check)==()
shall only be used for immutable types. Then use it to test for equality.
Of course the inversed counterparts are meant accordingly.
Here is a summary
== should test to see if the reference points to the same location whereas ReferenceEquals tests to see if they contain the same data
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