While bool? Take the following example, which will not compile. Like I mentioned above, the Equals method derives from the base object type. Changing the behavior of the method can be accomplished by any implemented class type in C. If the implementor does not override the behavior in a new class, determining equality is done by reference. In other words, are the objects being compared occupying the same space in memory? Using the Equals method with numbers gets us a confusing result.
Why did that occur? Remember how I mentioned that each type decides how it implements the Equals method. In the case of most primitive types, they choose not to override the method.
The language bases its results on the memory location of our values and not their numeric values. Well, comparing numeric values with Equals did not get us the results we expected.
What results do you expect comparing strings with the Equals method? In this case, they are equivalent. A nice bonus of using the Equals operator on strings, is it comes overloaded to take a StringComparison enum to make case insensitive comparisons. Note: be careful that x is not null, or else your application will throw a null reference exception. Comparing values is fundamental to all programming languages, and C is no different. And touches well on string interning.
When multiple string literals are identical, the compiler is smart enough to use the same address for both references because strings in. NET are immutable. Show 7 more comments. When I'm working with a new type whose definition is in flux or writing generic algorithms, I find the best practice is the following If I want to compare references in C , I use Object. Amen Jlili 1, 2 2 gold badges 22 22 silver badges 51 51 bronze badges.
JaredPar JaredPar k gold badges silver badges bronze badges. On the other hand, I can see where this stems from and why it might be desirable to make the semantics explicit. It's short and unambiguous.
Konrad, I really should have said "when I'm unfamiliar with a type, i find the best practice is the following". Yes VB has much better semantics here because it truly separates value and reference equality. C mixes the two together and it occasionally causes ambiguity errors.
This is not entirely true. It can only be overloaded, which is an important difference. Here is an actual link for now to the mentioned article: docs. Add a comment. If operands are Reference Types with exception of string and both refer to the same instance same object , it returns true else false. If operands are string type and their values are equal, it returns true else false.
Equals If operands are Reference Types , it performs Reference Equality that is if both refer to the same instance same object , it returns true else false. Robert Synoradzki 1, 11 11 silver badges 17 17 bronze badges. This is not correct. Describing a special-case exception only for string misrepresents the operator's semantics.
It would be more accurate, though perhaps not terribly useful, to say "if operands are reference types it returns true if the operands refer to the same object, unless there is an applicable overload, in which case the implementation of that overload determines the result".
The same is true for Equals with the added complication that it is a virtual method, so its behavior can be overridden as well as overloaded. Equals compares object content. String datatypes always act like content comparison. I hope I'm correct and that it answered your question. Yousha Aleayoub 3, 4 4 gold badges 44 44 silver badges 59 59 bronze badges.
Firstly, there is a difference. Equals 2. Colonel Panic Colonel Panic k 76 76 gold badges silver badges bronze badges. For example, should Comparisons among integral types are fine, but floating-point comparisons should only be performed IMHO with values that are explicitly cast to matching types.
The comparison of a float to something other than a float , or a double to something other than a double , strikes me as a major code smell that should not compile without diagnostics. Pascal's div and even VB. As for the relation you suggest, even if x and y are both float or both double , x.
That's normal, because Equals 's first parameter is a string! This is why the compiler will give you a warning saying: Possible unintended reference comparison; to get a value comparison, cast the left hand side to type 'string'.
MikeKulls MikeKulls 2, 1 1 gold badge 22 22 silver badges 30 30 bronze badges. DominicCronin: Always observe the compile-time warnings.
It checks for reference equality. Whether that will give true or false can be hard to predict because of string interning.
BlueMonkMN's code shows that, though not with casting. Ole Albers Ole Albers 7, 8 8 gold badges 59 59 silver badges bronze badges. Equals method - better where MyString is a variable that comes from somewhere else in the code. Equals "Somestring", MyString ; It is a little more to write, but in my opinion, safer to use.
Here is some info copied from Microsoft: public static bool Equals string a, string b ; Parameters a String The first string to compare, or null. Returns Boolean true if the value of a is the same as the value of b ; otherwise, false.
Community Bot 1 1 1 silver badge. Mario Levesque Mario Levesque 10 10 silver badges 9 9 bronze badges. Mehmet Aras Mehmet Aras 5, 1 1 gold badge 23 23 silver badges 31 31 bronze badges. You have it back to front. Equals s2 ; Console. Equals s3 ; Console. Equals s4 ; Console.
Equals s5 ; Console. LearnCocos2D 64k 20 20 gold badges silver badges bronze badges. Novichok Novichok 44 3 3 bronze badges. Adding one more point to the answer. Bala Bala 7 7 bronze badges. Equals Object in a manner that provides value equality. The Point. Equals method checks to make sure that the obj argument is not null and that it references an instance of the same type as this object. If either check fails, the method returns false.
Equals method calls the GetType method to determine whether the run-time types of the two objects are identical. If the method used a check of the form obj is Point in C or TryCast obj, Point in Visual Basic, the check would return true in cases where obj is an instance of a derived class of Point , even though obj and the current instance are not of the same run-time type. Having verified that both objects are of the same type, the method casts obj to type Point and returns the result of comparing the instance fields of the two objects.
In Point3D. Equals , the inherited Point. Equals method, which overrides Object. Equals Object , is invoked before anything else is done. If it is a Point3D object, it is cast to a Point object and passed to the base class implementation of Equals. Only when the inherited Point. Equals method returns true does the method compare the z instance fields introduced in the derived class. The following example defines a Rectangle class that internally implements a rectangle as two Point objects.
The Rectangle class also overrides Object. Equals Object to provide for value equality. Some languages such as C and Visual Basic support operator overloading. When a type overloads the equality operator, it must also override the Equals Object method to provide the same functionality. This is typically accomplished by writing the Equals Object method in terms of the overloaded equality operator, as in the following example. Because Complex is a value type, it cannot be derived from.
Therefore, the override to Equals Object method need not call GetType to determine the precise run-time type of each object, but can instead use the is operator in C or the TypeOf operator in Visual Basic to check the type of the obj parameter.
The type of comparison between the current instance and the obj parameter depends on whether the current instance is a reference type or a value type.
If the current instance is a reference type, the Equals Object method tests for reference equality, and a call to the Equals Object method is equivalent to a call to the ReferenceEquals method. Reference equality means that the object variables that are compared refer to the same object. The following example illustrates the result of such a comparison. It defines a Person class, which is a reference type, and calls the Person class constructor to instantiate two new Person objects, person1a and person2 , which have the same value.
It also assigns person1a to another object variable, person1b. As the output from the example shows, person1a and person1b are equal because they reference the same object. However, person1a and person2 are not equal, although they have the same value. If the current instance is a value type, the Equals Object method tests for value equality. Value equality means the following:.
The two objects are of the same type. As the following example shows, a Byte object that has a value of 12 does not equal an Int32 object that has a value of 12, because the two objects have different run-time types. The values of the public and private fields of the two objects are equal. The following example tests for value equality.
It defines a Person structure, which is a value type, and calls the Person class constructor to instantiate two new Person objects, person1 and person2 , which have the same value. As the output from the example shows, although the two object variables refer to different objects, person1 and person2 are equal because they have the same value for the private personName field.
Because the Object class is the base class for all types in the. NET Framework, the Object. Equals Object method provides the default equality comparison for all other types.
However, types often override the Equals method to implement value equality. For more information, see the Notes for Callers and Notes for Inheritors sections. When you call the Equals Object method overload on a class in the Windows Runtime, it provides the default behavior for classes that don't override Equals Object. This is part of the support that the.
Classes in the Windows Runtime don't inherit Object , and currently don't implement an Equals Object method. NET Framework provides the default behavior for these methods. Derived classes frequently override the Object. Equals Object method to implement value equality. When you call the Equals method to test for equality, you should know whether the current instance overrides Object.
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