Active Oldest Votes. Improve this answer. Jon Skeet Jon Skeet 1. I have a feeling that something is lost due to a language barrier Mars: But there's no such concept in C for a general object. There's the concept of an empty array, or an empty list etc - but you'd need to check for that specifically. I know. Just think thats possibly where this question was coming from, even if it wasn't asked very clearly — Mars.
Mars: Have added a paragraph at the end of the answer to help with that. The Overflow Blog. Podcast Making Agile work for data science. Stack Gives Back A query provider is a library that translates C query expressions into a native data format, such as Entity Framework Core. Query providers implement the System. IQueryProvider interface to create data sources that implement the System. Skip to main content. This browser is no longer supported.
Download Microsoft Edge More info. It would not be wrong to say that Null values are equally important and cannot be overlooked in any programming language, and this is so in C as well.
Here the Null values can be treated in many ways, and they are just a few cases of them. In this post, we discussed in detail about these keywords of C. However, Null Coalescing has certain advantages and disadvantages as well as if it is incorporated inside the code then it can decrease the number of lines of the code.
Though it cannot improve the performance of speed of the program but can optimize the code. As a result, the code becomes easier to understand. View All. Manchun Kumar Updated date Aug 13, Let us start our discussion with an example where we will assign a NULL value to a value type variable,.
This problem can be solved in the following two ways,. These are the ways to convert a non-nullable value type to nullable value type in C. A nullable type has two members,. HasValue is a Boolean type value that can again have two types of values one in True and other is False.
In short, the kind of comparison behavior you get can vary significantly, depending on which method you choose to call. One comment here, however: Microsoft doesn't officially document the internal behavior of Object.
Equals a,b. If you need an iron clad gaurantee of comparing a reference to null without any other code running, you want Object. ReferenceEquals :. This method makes the intent extremently clear - you are specifically expecting the result to be the comparison of two references for reference equality. The benefit here over using something like Object. Equals a,null , is that it's less likely that someone will come along later and say:.
Let's inject some pragmatism here, however. So far we've talked about the potential for different modalities of comparison to yield different results. Furthermore, they are sealed - preventing any change to their behavior through inheritance.
The following is quite common and correct :. See the next part. Equals a, b ". Equals b ". For example, "this. Equals b " is safe. Or if "a" is a field that is initialized at construction time, and the constructor throws exception if null is passed in as the value to be used in that field. Q: Are these susceptible to being overridden in some class, with code that does not handle null correctly, resulting in an exception?
But should you? The bug would be in that hypothetical future bad class , and it would be a straightforward type of failure. Easy to debug and fix by whoever supplies the class.
I doubt it is a problem that happens often, or persists long when it does happen. More detailed A: Object. Equals a, b is most likely to work in the face of a poorly written class. If "a" is null, the Object class will handle it itself, so no risk there. The called method merely has to work correctly when "b" is null. Unless the called method is extremely poorly written, the first step it does is determine whether "b" is a type that it understands.
So Object. The framework guidelines suggest that you treat Equals as value equality checking to see whether two objects represent the same information, i. So, assuming the guidelines apply here, pick whichever is semantically sensible. In reference to " Which implementation gets called is determined at compile time based on the static type s.
In other words, there is no way for an external library to provide a different version of the routine to your compiled code. I ended up here when I was trying to compare the unique Id of objects that could themselves be null. Found it easier to just impute the missing data first, and then do the comparison. Stack Overflow for Teams — Collaborate and share knowledge with a private group.
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