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Find centralized, trusted content and collaborate around the technologies you use most. Connect and share knowledge within a single location that is structured and easy to search. Equals returns true. Equals is just a virtual method and behaves as such, so the overridden version will be used which, for string type compares the contents.
If two objects you are comparing are referring to the same exact instance of an object, then both will return true, but if one has the same content and came from a different source is a separate instance with the same data , only Equals will return true.
The following code illustrates the subtle differences in behaviors:. Equals are both dependent upon the behavior defined in the actual type and the actual type at the call site. In my experience, I find it’s common for people to implement.
This means that. 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. Reference equals in the code to remove the ambiguity. Eric Lippert recently did a blog post on the subject of why there are 2 methods of equality in the CLR. It’s worth the read. I would add that if you cast your object to a string then it will work correctly.
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’. Just as an addition to the already good answers: This behaviour is NOT limited to Strings or comparing different numbertypes. Even if both elements are of type object of the same underlying type.
Because the static version of the. Equal method was not mentioned so far, I would like to add this here to summarize and to compare the 3 variations. In C there’s no practical difference for comparing strings using Method 1 or Method 2 as long as both are of type string.
However, if one is null, one is of another type like an integer , or one represents an object that has a different reference, then, as the initial question shows, you may experience that comparing the content for equality may not return what you expect.
Equals when comparing things, you can use the static String. Equals method instead. This way, if the two sides are not the same type you will still compare the content and if one is null, you will avoid the exception. If both a and b are null , the method returns true. I am a bit confused here. However, since this does not appear to be the case, then runtime type of Content is not string and calling Equals on it is doing a referential equality and this explains why Equals “Energy Attack” fails.
There is another dimension to an earlier answer by BlueMonkMN. The additional dimension is that the answer to the Drahcir’s title question as it is stated also depends on how we arrived at the string value.
To illustrate:. EqualsTo method gives you provision to compare against culture and case sensitive. I am sharing the results below Please correct or advise if I am wrong somewhere. If the compiler finds such an overload it will use it.
If neither condition applies, compilation will fail. Note that some other languages use separate tokens for the two equality-check operators. In VB. As it is, since no such operator is defined, C will promote the int to float , rounding it to f before the equality-check operator sees it; that operator then sees two equal floating-point numbers and reports them as equal, unaware of the rounding that took place.
For instance, in the following example, at runtime, it will be decided that the Equals will apply on int values, the result is true. Note that Equals uses structural comparison for struct , which means it calls Equals on each field of a struct. But what if I make them different?
For example:. When we create any object there are two parts to the object one is the content and the other is reference to that content. See here for more explanation. Stack Overflow for Teams — Start collaborating and sharing organizational knowledge.
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Improve this question. Drahcir Drahcir See also: stackoverflow. The Content property is object. With Equals, the call goes to the virtual method object. Equals object ; string overrides this method and performs an ordinal comparison on the string content. See msdn. So read the compile-time warnings! If I remember correctly, the warning text suggests just that. Even better: turn on the warnings-as-errors option to force everyone to pay attention to them. Show 1 more comment.
Sorted by: Reset to default. Highest score default Trending recent votes count more Date modified newest first Date created oldest first. Improve this answer. Unless the operator is specifically implemented in the class — Dominic Cronin. DominicCronin This isn’t true. It looks like operator overloads are determined at compile time and at compile time all it knows is that the left hand side is an object. They are quite different which is why. To be clear, object type notice the monospace font is technically meant to be “an expression of type System.
Object “. It does not have anything to do with the runtime type of the instance that is referred to by the expression. I think the statement “user-defined operators are treated like virtual methods” is extremely misleading. They are treated like overloaded methods and only depend on the compile-time type of the operands. In fact, after the set of candidate user-defined operators is computed, the rest of the binding procedure will be exactly the method overload resolution algorithm — mmx.
DominicCronin The misleading part is that virtual method resolution depend on the actual runtime type of an instance, whereas that is completely ignored in operator overload resolution, and that is indeed the whole point of my answer.
Show 5 more comments. AustinWBryan 3, 3 3 gold badges 19 19 silver badges 39 39 bronze badges. Spot on. Equals compares object content deep comparison. As mehrdad said,. Equals is overridden to provide that deep content comparison. So String is a bad example to use here, as it doesn’t help us understand the general case where no custom operator has been defined. 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. 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, 3 3 gold badges 24 24 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.
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