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.NET Forum / .NET Framework / New Users / October 2007When to use class and when structure
Hi, When to use class and when structure in our application? Thanks, Bhuwan > Hi, > > When to use class and when structure in our application? I think it would be hard, if not impossible, to come up with a good, 100% reliable way to describe when to use one or the other. However, generally speaking: A struct is a good choice for relatively small data types, especially if they will always be contained in something else or kept as a local variable and where the data type is more about storing data than doing something. As value types, they can have lower overhead than a class in certain situations and are often better-suited to immutable types (in fact, one could argue that it's a bad idea to make a mutable struct). A class is a good choice for more complex data types, especially for those that represent some sort of abstract type that has a behavior as opposed to simply storing values. They are required if you want to take advantage of OOP techniques based on inheritance. Since classes are a reference type, you'll want to use a class when you will benefit from being able to have multiple references to the same instance of data or otherwise want to use a reference to access the data (passing as a parameter, for example). For what it's worth, I almost never create a struct. :) I almost always want the flexibility and inheritance features of a class. It does depend on the exact situation though. Pete > When to use class and when structure in our application? If in doubt, use a class. Structures can be used for some small types, mostly for performance reasons. If you implement an enumerator, for example, it might make sense to make it a structure. If you want to use structures, you should read up on how they work exactly.  SignatureGöran Andersson _____ http://www.guffa.com Thanks all Bhuwan > Hi, > [quoted text clipped - 3 lines] > > Bhuwan Another consideration is that a class is a reference type while a structure is a value type. So, if you want to create copies of instances instead of references when assigning, structures provide a simple way to ensure that this is done. That is, if you want assignments to default to copies or values rather than references, use a structure. This is one way to prevent accidental modification of the data in the original entity. For example: someClass a = new someClass(); someStruct b = new someStruct(); someClass c; someStruct d; a.foo = 5; c = a; c.foo = 10; // a.foo also equals 10 now, as c is a reference to a b.bar = 5; d = b; d.bar = 10; // b.bar is still equal to 5 SignatureHTH, Kevin Spencer Chicken Salad Surgeon Microsoft MVP > Thanks all > Bhuwan [quoted text clipped - 6 lines] >> >> Bhuwan > Another consideration is that a class is a reference type while a structure > is a value type. So, if you want to create copies of instances instead of > references when assigning, structures provide a simple way to ensure that > this is done. That is, if you want assignments to default to copies or > values rather than references, use a structure. This is one way to prevent > accidental modification of the data in the original entity. Just be aware that: 1) This is a shallow copy. If the struct itself contains reference types, only the references are copied. And, 2) It's not hard to implement the same behavior in a class. If a shallow copy is sufficient, then it's trivial to add a Clone() method (implementing IClonable) that calls Object.MemberwiseClone() to do the same. Personally, I wouldn't call the copying behavior of a struct a significant difference between the two, given the above. But if it's a difference that's of interest, one should at least be aware of the subtleties related to that difference. Pete Good points Peter. Especially the first. I mentioned the value/reference aspect because there are definitely times when composite types of value types definitely benefit from being structs rather than classes. But I did neglect to mention the "gotcha" of structs containing reference types. SignatureHTH, Kevin Spencer Chicken Salad Surgeon Microsoft MVP >> Another consideration is that a class is a reference type while a >> structure is a value type. So, if you want to create copies of instances [quoted text clipped - 19 lines] > > Pete In addition to what the other responders said. The most common place I use struct is if I have a function that needs to return more than 1 value. For example, suppose you had a function that did integer division. You may want to return a struct that contained both the quotiant and remainder. SignatureAndrew Faust andrew[at]andrewfaust.com http://www.andrewfaust.com > Hi, > [quoted text clipped - 3 lines] > > Bhuwan > struct is if I have a function that needs to return more than 1 value. For Kindly explain how a function can return more than one value? Thanks, Bhuwan > In addition to what the other responders said. The most common place I use > struct is if I have a function that needs to return more than 1 value. For [quoted text clipped - 8 lines] >> >> Bhuwan >> struct is if I have a function that needs to return more than 1 >> value. For > Kindly explain how a function can return more than one value? By putting the values into a struct, and then returning the struct. As far as the compiler knows, the function is return a single value: the struct itself. But logically, the function returns as many "values" as the struct contains. Pete SignatureI'm trying a new usenet client for Mac, Nemo OS X. You can download it at http://www.malcom-mac.com/nemo Free MagazinesGet these publications absolutely FREE for up to 12 months. There are no hidden fees and no obligation. Simply choose a title, complete the application form and submit it. Read more ...
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