Thalia: Über 10 Mio Bücher ❤ Immer versandkostenfrei ✓ Lieferung nach Hause oder in die Filiale ✓ Jetzt»A Programmer’s Guide to C# «online bestellen!. Eric Gunnerson One of the “late breaking” features in C# is what is known as “Nullable Types”. The details can be found in the C# language spec. Ung?ltige Konvertierung von der Zeichenfolge " in Typ Date. Buy Programmer’s Introduction to C# from Dymocks online BookStore. Find latest reader to C# Nick Wienholt, Eric Gunnerson, Anders Hejlsberg.
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One of the “late breaking” features in C 2. The details can be found in the C 2. Nullable types address the scenario where you want to be able to have a primitive type with a null or unknown value.
This is common in database scenarios, but is also useful in other situations. To make this easier, in VSwe’re introducing a new type named “Nullable”, that looks something like this it’s actually more complex than this, but I want to keep the example simple:.
You can use this struct directly, but we’ve also added some shortcut syntax to make the resulting code much cleaner. The first is the introduction of a new syntax for declaring a nullable type. Finally, we have support to make writing expressions easier. If I wanted to add two nullable ints together and preserve null values, if I didn’t have language support, I would need to write:.
At least I think that’s what I’d have to write – it’s complex enough that I’m not sure this code works. This is ugly enough that it makes using Nullable without compiler support a whole lot of work. With the compiler support, you write:. You must be logged in to post a comment.
Is a nullable type a child type? For example the framework already has a nullable integer SqlInt32, and I hope its arithmetical operators do null propogation for you. BTW, I am glad you guys came around to the default T eirc of thinking. This was one of my major complaints and one that I fought for like crazy in the newsgroups!
This is convenient because SQL behaves the same way. That is, any mathematical expression with a etic value in it, returns null. What would be a whole gunnetson MORE useful [request!! The main thing is, it should be almost trivial to gunnerdon from the compiler standpoint, and would provide a quantum leap in program robustness [well, for us, program readability as our code standards ensure that every single public function, constructor, or property setter check each variable is not null — our code would halve in size!
I really love the propagation of null values. For those who know the functional language Haskell http: I hope you and the other language designers know what you are doing for the long run. The current C language is thing of beauty with very few warts. Please do a lot of usability testing with the syntax of this feature.
I can see a need but I really think it should be done as a keyword and not an operato. Is immediately obvious what we are doing. How can a bool have three values! I agree that nullable int looks so much better. But I wonder most about why I need this? In fact, I think I will avoid them as the syntax confuses me. Not very C -ish. Are there already any guidelines how to use this with the two primitive gunnreson that already inherently provide a similar feature, albeit in a completely different way?
There will be obvious cases where one or another will be better, but did someone contemplate the effects of choosing one option over another already? Take a look at the whole vn at http: Another feature that makes it easier to mess things up along with anonymous methods. Was there a big demand for this? VB has Nullable types and all other generics as well. See the VB Blog at: OK, gunnerso skimming the MS Research paper, I see there is a lot more going on with v# special operators int?
Nullable types in C# – Eric Gunnerson’s Compendium
Add every feature as a language feature and apply lots of rules to avoid all this complexity to be abused. Beware, there is a real life counterpart to this: The laws that regulates the ericc security benefits in almost any country. These laws are so complex that nobody understands them. Every attempt to simplify them has failed, at least in my country. Talk about unmaintainable legacy code! While I can only approve the introduction of generics and iterators in Ctwo things that are necessary and useful, I must say that I have serious doubts about anonymous methods and nullable types.
The one thing I liked about C as it emerged, was its relative simplicity. Many keywords too gunerson, some sayand yet a few relatively simple concepts. However, with the multi-language support the. NET platform has, I would have expected new languages or new class libraries instead of new features to existing languages. I can only hope the design team gunnreson considered all implications and that the new features will follow the principle “pay as you go” — developers not using the new features should not be subjected to performance or other kinds of penalties.
Will it work in the release version? I must say that C is gumnerson nice language but it misses one of the cc# things that makes for widespread adoption of it by developers… cross platform compatibility. The reason why Java became so popular was that you write code once and then use it anywhere. The whole idea behind OOP is that gunnersoh plan on reusing code. And what good is it if I can only reuse that code on one platform? You have hit your target demographic. But to get web developers to use it when Apache is the most popular web server and to get system administrators or application developers for portable devices to use it is not very likely.
The project is getting no support from Microsoft who can at anytime change gunnfrson spec and make all that code funnerson. The only reason I make this whole point is that I spent the last few months making a long decision of what to use… Java or C for my next project. I researched eirc both and they both have a similar level of functionality Java is still a bit faster but Microsoft makes up for this by integrating the virtual machine into their OS.
And what it finally came down to was that I plan to be doing web development and portable applications. And when you consider that, Java is the natural choice. My code can go anywhere. Nathan, I was with you up to the part about using C to develop desktop apps.
I personally prefer C and WinForms. Eric Gunnerson blogged last erjc about Nullable types in C 2. This new C feature will allow one to specify a Type like int? Nullable types in C????? IMO, by default all objects should have cardinality 0 or 1! So string should be the same as string!
But I always care about the structure of my data i. Then again, just an opinion.
Nullable types in C#
Are there any statistics, or polls out there which present the options? So can we assume that the next generation of typed DataSets gunerson utilize this feature and do away with the horrible IsFieldNameNull convention?
This compiles but I get a runtime error.
I looked and strongly typed datasets are not using gunneraon feature. We are still stuck with “IsFieldNameNull ” methods.
I kinda think this is just syntactical sugar. The syntax can hide far more complexity and make it difficult down the line. To the down in the trenches programmer, this kind of syntax will become very confusing. It is simply not needed. One of the features I value most about C is simplicity.
While it is currently a little more complex than I think it should be, adding this type of complexity on vkn as simple as a null seems a step backward. It will cost more in debugging and code research due to incompatible types along with cluttering up your code with symbols that have meaning on their own beyond this use. Do not understand why other value types cannot address null as simply as “string” does today.
While, I do have a problem erif a null string and string. Code will become more c and debugging time will increase. For me it is simplicity, which equates to less development time, easier to maintain and less debugging.
You increase any of those, C suffers along with.
A curly bracket is the same size as a question mark. If you cant see a question mark, you shouldnt be programming in C. Anyway, thanks for that inconoclastic bombshell of a comment.
So null is a natural, valid state for a reference type. The one thing I am not sure I like is the function syntax changes like:. At least in Java there were corresponding wrapper types, so you could do something like:. I like the idea of this in C:.