#Does not equal sign in notepad code#

But there are a few important details to add, regarding consitency. With that, it might be tempting to wrap up this post and declare it done. That is exactly what the IEquatable interface does. In some cases it also makes sense to mark a type as implementing the a more specific version of. Equals(Object) method from Object, so it can be used on any type in the. The IEquatable InterfaceĪll types inherits the.

Providing a specialized overload with the right type can give some performance improvements, so for library code like String it’s a good idea to provide that overload. The only difference between them is that the former has to cast the parameter, which is a small performance penalty. Which means that in one case String.Equals(Object) will be called and in the second case String.Equals(String). But, the overload resolution is done on the static (i.e. The method is virtual so in both cases, an overload of. Equals (s2 ) ) // TrueĬonsole.WriteLine(s2.Equals(o1)) // TrueĬonsole.WriteLine(o1.Equals(s2)) // True Adjusting the code above to use Equals shows the difference.Ĭonsole. It is virtual and allows each class to define it’s own behaviour. When the dynamic type of the objects need to be taken into consideration, the. For the other few percent of comparisons, something more powerful is needed.Equals(Object) So = will be a reasonable default for the 90%+ of cases in a program where no inheritance is involved and the compile time type of the references is the same as the run time type. Since it is resolved at compile time it simply can’t deal with inheritance. The verdict for = is that it behaves consistent until inheritance is involved. WriteLine (s2 = o1 ) // FalseĬompiling the code will give a warning: Possible unintended reference comparison to get a value comparison, cast the left hand side to type ‘string’. Using the strings from the previous example, we’ll treat one of them as an objectĬonsole. It’s enough to cast one of the operands to object to get the default reference comparison.

If the references are cast to another type, such as object the custom operator won’t be used. The decision to use it or not will be done entirely at compile time. In fact, all of them override the = operator by implementing the public static bool operator =. Var u1 = new Uri(' var u2 = new Uri(' Console.WriteLine(u1 = u2) // TrueĬonsole.WriteLine(object.ReferenceEquals(u1, u2)) // FalseĬonsole.WriteLine(object.ReferenceEquals(v1, v2)) // False Overloaded Operator =įor string, Uri and Version the default implementation of = is obviously not used, but instead a more specific overload is provided by the framework. a way to get two different string instances with the same value.Ĭonsole.WriteLine(object.ReferenceEquals(s1, s2)) // False Strings are highly optimized to share storage space. ReferenceEquals (u1, u2 ) ) // False var v1 = new Version ( 1, 2, 3 ) var v2 = new Version ( 1, 2, 3 ) Ĭonsole. ReferenceEquals (s1, s2 ) ) // False var u1 = new Uri ( ' ) var u2 = new Uri ( ' ) Ĭonsole. var s1 = 'Blue' var sb = new StringBuilder ( 'Bl' ) Using a StringBuilder is // a way to get two different string instances with the same value. If we put the current date in two variables we expect them to be equal.

Looking at more complex value types such as DateTime it also makes sense.

Looking first at simple value types, this makes sense and makes comparisons of e.g. For the string type, = compares the values of the strings. For reference types other than string, = returns true if its two operands refer to the same object. The most common way to compare objects in C# is to use the = operator.įor predefined value types, the equality operator (=) returns true if the values of its operands are equal, false otherwise. In this post, we’ll take a closer look at the basics: = and. There’s also a Object.ReferenceEquals(Object, Object) method that can be used. In C# objects can be compared with the = operator, with the Equals(Object) member, with the Object.Equals(Object, Object) method or using custom comparators that implement one of or more of the IEquatable, IComparable, IStructuralEquatable or IStructuralComparable interfaces. Equality might look like a simple concept at a first glance, but looking deeper it isn’t.

#Does not equal sign in notepad code#