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Cannot Modify The Result Of An Unboxing Conversion Struct

I have an ArrayList instance to which I add two types of elements. Baden Württemberg Ticket usage Why does low frequency RFID have a short read range? Thursday, October 01, 2009 3:24 PM 0 Sign in to vote for (int i = 0; i < instruments.Count; i++) { ((VCV)htVCV[i]).Mean = Mathematik.Statistics.Mean((double[])htVCV[i]); } I changed over the struct to return i; } } return0; } Facebook Twitter YouTube malmaa View Public Profile Send a private message to malmaa Find More Posts by malmaa 01-17-2010, 10:38 PM #2 NinjaTrader_Austin Check This Out

Struct “Osto” contains IOrders like Oe1, Oe2, Os1, Os2 and Ol1 along with other data types. In other words, either the value type need to define a casting operator that can cast to that other type, or that other type need to define a casting operator that Password NinjaTrader Register FAQ Members List General Programming General NinjaScript programming questions. Unboxing it does create a copy, even if you don't assign it to a variable. –Servy Jun 24 '13 at 17:12 4 @colinfang If you want to follow the rules http://stackoverflow.com/questions/17280547/why-can-i-not-modify-the-result-of-an-unboxing-conversion

From: Ignacio Machin \( .NET/ C# MVP \) Re: Cannot modify the result of an unboxing conversion? Regards Ralph Facebook Twitter YouTube Ralph View Public Profile Send a private message to Ralph Find More Posts by Ralph 01-19-2010, 04:34 AM #8 malmaa Member Join Date: Your source code is: for (int i = 0; i < instruments.Count; i++) { VCV v = new VCV(); htVCV.Add(i,v); } I urge you to use Dictionary<> instead of Hashtable - The views and opinions expressed in this forum are those of the authors and do not necessarily reflect the official policy or position of NT or NTB. -- Fixed Width ----

The difference is important for some topics such as generic variance - that only works with reference types because of the reference conversions available. If you change the value of a field within that copy, it won't do what you want. Ref.types - casting?10Do all C# casts result in boxing/unboxing9In C#, why can a single cast perform both an unboxing and an enum conversion?1Trying to understand Type Casting & Boxing/Unboxing2Boxing and Unboxing4does It is possible to define metric spaces from pure topological concepts without the need to define a distance function?

That's why the line in which you do that compiles. But you're writing your code in C#, so your code follows the rules of C#. I Unbox the values as I read from the ArrayList “List”. find more info Maybe some community members can help you out.

Classes are reference types and don't need to be boxed. However, in the case of the struct type element, C# won't allow it. Regards Ralph Facebook Twitter YouTube Ralph View Public Profile Send a private message to Ralph Find More Posts by Ralph 12-13-2012, 03:03 PM #14 forrestang Senior Member Join DateTime is an example: you can't *change* the "seconds" (for example) of an existing DateTime - you can, however, swap the structure for a different one, created either via a constructor,

Alternatively, just use a class instead of a struct. you could try here This might be a general C# question. I made a mistake: I mean, so UNboxing is just kind of casting? –Lojol Jan 19 '11 at 11:57 @Lojol: Yes, the same casting syntax is used for both That's where the copy comes in.

I now get an invalid cast excpetion Unable to cast object of type 'VCVDemo.VCV' to type 'System.Double[]'. his comment is here All the comments in your code are correct. This is the origin of the saying, "Mutable structs are evil". –Servy Jun 24 '13 at 16:42 1 @Servy But what if I don't throw away the copy, and I However, if you are doing the following then all list elements would point to the same Osto() instance: Osto Local = new Osto(...); for (int i = 0; i < 10;

Sometimes I need to change the field values of the elements held by the ArrayList. Was a massive case of voter fraud uncovered in Florida? You could try using a Dictionary instead (which is pretty much a strongly-typed hash table). this contact form My Code: // struc containing info of stops, limits, IOrders of Positions that opened at an instance privatestruct Osto {publicdouble op;publicdouble st;public DateTime tm;public IOrder oe1;public IOrder oe2;public IOrder os1;public IOrder

A very simple modification in my code. You’ll be auto redirected in 1 second. He's changed to using classes now, so he will be able to.

You don't need any sort of cast expression to box though - for example your second line of code contains a boxing operation but no cast expression.

The first type of element is a class, the other type of element is a struct. How can I declare independence from the United States and start my own micro nation? Can dispel magic end a darkness spell? Where do I drop off a foot passenger in Calais (P&O)?

share|improve this answer answered Jan 19 '11 at 11:48 Ian 20.2k1453139 add a comment| up vote 1 down vote One important restriction on unboxing is that you can only unbox to Many (the majority of) classes are mutable. That is incorrect. http://scriptkeeper.net/cannot-modify/cannot-modify-the-result-of-an-unboxing-conversion.html Another way is using a temp variable.

Alternatively, just use a class instead of a struct. Firstly, having a mutable struct is generally a bad idea - it's likely to bite you sooner or later. First it unboxes to int, and then converts to long Another interesting bit is that a nullable value-type gets boxed as it's non nullable type, and can be unboxed as both I have tried the following code: for (int i = 0; i < instruments.Count; i++) { ((VCV)htVCV)[i].Mean = Mathematik.Statistics.Mean(((double[])htCandles.Values)); } But I have the following error Cannot modify the result of

To create an instance of a class in general, we use Osto Var = new Osto(); (where Var is an instance of the class not a list) Since we are using For example, Point^ (strongly-typed box) is actually represented as ValueType modopt(Point) modopt(IsBoxed). –svick Jun 24 '13 at 17:55 | show 1 more comment up vote 1 down vote You can't do Regards, Facebook Twitter YouTube malmaa View Public Profile Send a private message to malmaa Find More Posts by malmaa 01-18-2010, 06:07 PM #7 Ralph Senior Member Join Date: C# Copy // CS0445.CS class UnboxingTest { public static void Main() { Point p; p.x = 1; p.y = 2; object obj = p; // The following line generates CS0445, because

I know this is not the same as the original value (X). From the context of your reply I suppose it means that value type variables such as int and struct are inherently mutable, i.e. That's where the copy comes in. Cheers, Facebook Twitter YouTube malmaa View Public Profile Send a private message to malmaa Find More Posts by malmaa 01-18-2010, 08:00 AM #5 Ralph Senior Member Join Date:

asked 5 years ago viewed 2471 times active 4 years ago Upcoming Events 2016 Community Moderator Election ends Nov 22 Linked 66 What is the difference between casting and conversion? Regards, Facebook Twitter YouTube malmaa View Public Profile Send a private message to malmaa Find More Posts by malmaa 01-19-2010, 07:25 AM #11 Ralph Senior Member Join Date: It's quick & easy. I tend to think of a cast being present in source code, but a conversion is what should actually happen due to your code. (And sometimes a conversion can be implicit.)

The content you requested has been removed. Join them; it only takes a minute: Sign up Why can I not modify the result of an unboxing conversion? Browse other questions tagged c# boxing value-type or ask your own question. Thursday, October 01, 2009 3:22 PM 0 Sign in to vote Aye, you're right.

share|improve this answer edited Jun 24 '13 at 17:46 answered Jun 24 '13 at 16:42 cHao 55.2k1082124 2 But the code tries to look at the value of the copy, Related 27Boxing vs Unboxing2Boxing/unboxing - only value types? Karlsen 223k65437637 add a comment| up vote 1 down vote A cast is one form of conversion, basically. For initialisation purpose you have to go with (2).