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• Hidden Features of C#?

  - by Serhat Özgel

  This came to my mind after I learned the following from this question: where T : struct We, C# developers, all know the basics of C#. I mean declarations, conditionals, loops, operators, etc. Some of us even mastered the stuff like Generics, anonymous types, lambdas, linq, ... But what are the most hidden features or tricks of C# that even C# fans, addicts, experts barely know? Here are the revealed features so far: Keywords yield by Michael Stum var by Michael Stum using() statement by kokos readonly by kokos as by Mike Stone as / is by Ed Swangren as / is (improved) by Rocketpants default by deathofrats global:: by pzycoman using() blocks by AlexCuse volatile by Jakub Šturc extern alias by Jakub Šturc Attributes DefaultValueAttribute by Michael Stum ObsoleteAttribute by DannySmurf DebuggerDisplayAttribute by Stu DebuggerBrowsable and DebuggerStepThrough by bdukes ThreadStaticAttribute by marxidad FlagsAttribute by Martin Clarke ConditionalAttribute by AndrewBurns Syntax ?? operator by kokos number flaggings by Nick Berardi where T:new by Lars Mæhlum implicit generics by Keith one-parameter lambdas by Keith auto properties by Keith namespace aliases by Keith verbatim string literals with @ by Patrick enum values by lfoust @variablenames by marxidad event operators by marxidad format string brackets by Portman property accessor accessibility modifiers by xanadont ternary operator (?:) by JasonS checked and unchecked operators by Binoj Antony implicit and explicit operators by Flory Language Features Nullable types by Brad Barker Currying by Brian Leahy anonymous types by Keith __makeref __reftype __refvalue by Judah Himango object initializers by lomaxx format strings by David in Dakota Extension Methods by marxidad partial methods by Jon Erickson preprocessor directives by John Asbeck DEBUG pre-processor directive by Robert Durgin operator overloading by SefBkn type inferrence by chakrit boolean operators taken to next level by Rob Gough pass value-type variable as interface without boxing by Roman Boiko programmatically determine declared variable type by Roman Boiko Static Constructors by Chris Easier-on-the-eyes / condensed ORM-mapping using LINQ by roosteronacid Visual Studio Features select block of text in editor by Himadri snippets by DannySmurf Framework TransactionScope by KiwiBastard DependantTransaction by KiwiBastard Nullable<T> by IainMH Mutex by Diago System.IO.Path by ageektrapped WeakReference by Juan Manuel Methods and Properties String.IsNullOrEmpty() method by KiwiBastard List.ForEach() method by KiwiBastard BeginInvoke(), EndInvoke() methods by Will Dean Nullable<T>.HasValue and Nullable<T>.Value properties by Rismo GetValueOrDefault method by John Sheehan Tips & Tricks nice method for event handlers by Andreas H.R. Nilsson uppercase comparisons by John access anonymous types without reflection by dp a quick way to lazily instantiate collection properties by Will JavaScript-like anonymous inline-functions by roosteronacid Other netmodules by kokos LINQBridge by Duncan Smart Parallel Extensions by Joel Coehoorn

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• What's the recommended implemenation for hashing OLE Variants?

  - by Barry Kelly

  OLE Variants, as used by older versions of Visual Basic and pervasively in COM Automation, can store lots of different types: basic types like integers and floats, more complicated types like strings and arrays, and all the way up to IDispatch implementations and pointers in the form of ByRef variants. Variants are also weakly typed: they convert the value to another type without warning depending on which operator you apply and what the current types are of the values passed to the operator. For example, comparing two variants, one containing the integer 1 and another containing the string "1", for equality will return True. So assuming that I'm working with variants at the underlying data level (e.g. VARIANT in C++ or TVarData in Delphi - i.e. the big union of different possible values), how should I hash variants consistently so that they obey the right rules? Rules: Variants that hash unequally should compare as unequal, both in sorting and direct equality Variants that compare as equal for both sorting and direct equality should hash as equal It's OK if I have to use different sorting and direct comparison rules in order to make the hashing fit. The way I'm currently working is I'm normalizing the variants to strings (if they fit), and treating them as strings, otherwise I'm working with the variant data as if it was an opaque blob, and hashing and comparing its raw bytes. That has some limitations, of course: numbers 1..10 sort as [1, 10, 2, ... 9] etc. This is mildly annoying, but it is consistent and it is very little work. However, I do wonder if there is an accepted practice for this problem.

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• Invalid Cast Exception ASP.NET C#

  - by Shadow Scorpion

  I have a problem in this code: public static T[] GetExtras <T>(Type[] Types) { List<T> Res = new List<T>(); foreach (object Current in GetExtras(typeof(T), Types)) { Res.Add((T)Current);//this is the error } return Res.ToArray(); } public static object[] GetExtras(Type ExtraType, Type[] Types) { lock (ExtraType) { if (!ExtraType.IsInterface) return new object[] { }; List<object> Res = new List<object>(); bool found = false; found = (ExtraType == typeof(IExtra)); foreach (Type CurInterFace in ExtraType.GetInterfaces()) { if (found = (CurInterFace == typeof(IExtra))) break; } if (!found) return new object[] { }; foreach (Type CurType in Types) { found = false; if (!CurType.IsClass) continue; foreach (Type CurInterface in CurType.GetInterfaces()) { try { if (found = (CurInterface.FullName == ExtraType.FullName)) break; } catch { } } try { if (found) Res.Add(Activator.CreateInstance(CurType)); } catch { } } return Res.ToArray(); } } When I'm using this code in windows application it works! But I cant use it on ASP page. Why?

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• C# Lack of Static Inheritance - What Should I Do?

  - by yellowblood

  Alright, so as you probably know, static inheritance is impossible in C#. I understand that, however I'm stuck with the development of my program. I will try to make it as simple as possible. Lets say our code needs to manage objects that are presenting aircrafts in some airport. The requirements are as follows: There are members and methods that are shared for all aircrafts There are many types of aircrafts, each type may have its own extra methods and members. There can be many instances for each aircraft type. Every aircraft type must have a friendly name for this type, and more details about this type. For example a class named F16 will have a static member FriendlyName with the value of "Lockheed Martin F-16 Fighting Falcon". Other programmers should be able to add more aircrafts, although they must be enforced to create the same static details about the types of the aircrafts. In some GUI, there should be a way to let the user see the list of available types (with the details such as FriendlyName) and add or remove instances of the aircrafts, saved, lets say, to some XML file. So, basically, if I could enforce inherited classes to implement static members and methods, I would enforce the aircraft types to have static members such as FriendlyName. Sadly I cannot do that. So, what would be the best design for this scenario?

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• Sort List C# in arbitrary order

  - by Jasper

  I have a C# List I.E. List<Food> x = new List<Food> () ; This list is populated with this class Public class Food { public string id { get; set; } public string idUser { get; set; } public string idType { get; set; } //idType could be Fruit , Meat , Vegetable , Candy public string location { get; set; } } Now i have this unsorted List<Food> list ; which has I.E. 15 elements. There are 8 Vegetable Types , 3 Fruit Types , 1 Meat Types , 1 Candy Types I would sort this so that to have a list ordered in this way : 1° : Food.idType Fruit 2° : Food.idType Vegetables 3° : Food.idType Meat 4° : Food.idType Candy 5° : Food.idType Fruit 6° : Food.idType Vegetables 7° : Food.idType Fruit //Becouse there isnt more Meat so i insert the //next one which is Candy but also this type is empty //so i start from begin : Fruit 8° : Food.idType Vegetables 9° : Food.idType Vegetables // For the same reason of 7° 10 ° Food.idType Vegetables ...... .... .... 15 : Food.idType Vegetables I cant find a rule to do this. Is there a linq or List.Sort instruction which help me to order the list in this way? Update i changed the return value of idType and now return int type instead string so 1=Vegetable , 2=Fruit , 3=Candy 4=Meat

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• Sharepoint: Integrity of lookup fields after a list import

  - by driAn

  Hi there I got a question about the behavior of lookup fields when importing data. I wonder how the lookup fields behave when the list they point to is being replaced/imported. To explain the issue, I will provide a quick example below: As example, assume we have these two sharepoint lists: Product Types ------------- + Type Name + Code Nr + etc Products -------- + Product Name + Product Type (Lookup field to list "Product Types") + etc In my scenario, the Products List contains production data on the production Sharepoint platform. It is filled with data by the business users. However the Product Types list contains rather static data and is maintained by the developer. Now after a development cycle, the developer wants to deploy his new webparts and his new data (product types list). The developer performs the following procedure: On the dev machine: Export "product type" list using stsadm On the production machine: Delete all items in the "product type" list On the production machine: Import the "product type" list using stsadm This means we basically replace the "product type" list on the production server while keeping the "product" list as it is. Now the question: Is this safe? Will the lookup references break under certain circumstances? Any downside of this import/export procedure? What happens if someone accesses a "product" during the import? Will the (now invalid) reference clear its own content (become a null value). What happens if the schema of the "product type" list changes (new column)? Will this cause any troubles? Thanks for all feedback and suggestions!

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• How to transfer objects through the header in WCF

  - by Michael

  I'm trying to transfer some user information in the header of the message through message inspectors. I have created a behavior which adds the inspector to the service (both client and server). But when I try to communicate with the service I get the following error: XmlException: Name cannot begin with the '<' character, hexadecimal value 0x3C. I have also get exception telling me that DataContracts where unexpected. Type 'System.DelegateSerializationHolder+DelegateEntry' with data contract name 'DelegateSerializationHolder.DelegateEntry:http://schemas.datacontract.org/2004/07/System' is not expected. Consider using a DataContractResolver or add any types not known statically to the list of known types - for example, by using the KnownTypeAttribute attribute or by adding them to the list of known types passed to DataContractSerializer. The thing is that my object contains other objects which are marked as DataContract and I'm not interested adding the KnownType attribute for those types. Another problem might be that my object to serialize is very restricted in form of internal class and internal properties etc. Can anyone guide me in the right direction. What I'm I doing wrong? Some code: public virtual object BeforeSendRequest(ref Message request, IClientChannel channel) { var header = MessageHeader.CreateHeader("<name>", "<namespace>", object); request.Headers.Add(header); return Guid.NewGuid(); }

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• Adding a dynamic image to UITable View Cell

  - by Graeme

  Hi, I have a table in which I want a dynamic image to load in at the left-hand side. The table needs to use an IF statement to select the appropriate image from the "Resources" folder, and needs to be based upon [dog types]. The [dog types] is extracted from an RSS feed, and so the image in the table cell needs to match the each cell's [dog types] tag. Update: See code below for what I'm looking to do (only below it's for earthquakes, for me its pictures of dogs). I suspect I need to use - (UIImage *)imageForTypes:(NSString *)types { to do such a thing. Thanks. Updated code: This is for Apple's Earthquake sample but does exactly what I need to do. It matches images to the severity (2.0, 3.0, 4.0, 5.0 etc.) of every earthquake to the magnitude. - (UIImage *)imageForMagnitude:(CGFloat)magnitude { if (magnitude >= 5.0) { return [UIImage imageNamed:@"5.0.png"]; } if (magnitude >= 4.0) { return [UIImage imageNamed:@"4.0.png"]; } if (magnitude >= 3.0) { return [UIImage imageNamed:@"3.0.png"]; } if (magnitude >= 2.0) { return [UIImage imageNamed:@"2.0.png"]; } return nil; } and under - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath magnitudeImage.image = [self imageForMagnitude:earthquake.magnitude];

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• Is there a programming toolkit for converting "any file type" to a TIFF image?

  - by Ryan

  Hello, I've written several variations of a program. The purpose of the program is to convert "any file type" to a TIFF image represenation of that file, as if it were being printed using a printer. I'm currently using a third party printer driver that I send files to, and it outputs a TIFF image. This is nice, but it requires me to use Office Interop files, and interact with each individual processing application in order to print the files. I had previously tried a toolkit, called Apose .NET, which did not rely on Office Interop, and did not require any printer driver. It did the conversion all on its own and would create a TIFF image. The problem with Aspose .NET was that it did not support a wide variety of input file types. Most notably, it can't do Visio files. My project calls for the ability to create a TIFF image for virtually "any file type". (excluding exes, music files, and stuff) I know that finding something that handles literally any file type is probably not a very feasible task, so I figure if it can at least handle all the Office file types, Adobe types, and other major standard file types, then I can write a custom extension parsing module that uses those processing applications to do the printing of any file type that can be viewed using those applications. So, does anyone know of a toolkit that can do this? Preferably one that does not rely on Office or a printer driver. It does not have to be free, or open source. Or, if you know of an amazing printer driver that does this, I'm open to that too. Thanks in advance, Ryan

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• WPF Sizing of Panels

  - by Mystagogue

  I'm looking for an article or overview of WPF Panel types, that explains the sizing characters of each. For example, here are the panel types: http://msdn.microsoft.com/en-us/library/ms754152.aspx#Panels_derived_elements I've learned (by experiment) that UniformGrid can be given a fixed height, or it can be "auto" where it expands to fit available space. That is great, but what I wanted was for Uniform Grid to shrink to fit its internal content (particularly content that is provided dynamically, at run-time). I don't think it has that ability. So I'd like to know either what other Panel I could use for that purpose, or what Panel I should nest the UniformGrid inside of. But I don't just want an answer to that specific question. I want the sizing dynamics and capabilities of all the Panel types, in summary form, so I can make all these choices as needed. Online I find articles that cover only half the Panel types, and don't give as much information about sizing as I'm describing. Anyone know the link (or book) that has the info I'm seeking? p.s. Since I want the UniformGrid to shrink to the dynamic content I'm providing, I could just keep track of the total height of controls placed within, and then set the height of the UniformGrid. But it would be nice if WPF took care of this for me.

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• Invalid Cast Exception in ASP.NET but not in WinForms

  - by Shadow Scorpion

  I have a problem in this code: public static T[] GetExtras <T>(Type[] Types) { List<T> Res = new List<T>(); foreach (object Current in GetExtras(typeof(T), Types)) { Res.Add((T)Current);//this is the error } return Res.ToArray(); } public static object[] GetExtras(Type ExtraType, Type[] Types) { lock (ExtraType) { if (!ExtraType.IsInterface) return new object[] { }; List<object> Res = new List<object>(); bool found = false; found = (ExtraType == typeof(IExtra)); foreach (Type CurInterFace in ExtraType.GetInterfaces()) { if (found = (CurInterFace == typeof(IExtra))) break; } if (!found) return new object[] { }; foreach (Type CurType in Types) { found = false; if (!CurType.IsClass) continue; foreach (Type CurInterface in CurType.GetInterfaces()) { try { if (found = (CurInterface.FullName == ExtraType.FullName)) break; } catch { } } try { if (found) Res.Add(Activator.CreateInstance(CurType)); } catch { } } return Res.ToArray(); } } When I'm using this code in windows application it works! But I cant use it on ASP page. Why?

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• Is it valid to use unsafe struct * as an opaque type instead of IntPtr in .NET Platform Invoke?

  - by David Jeske

  .NET Platform Invoke advocates declaring pointer types as IntPtr. For example, the following [DllImport("user32.dll")] static extern IntPtr SendMessage(IntPtr hWnd, UInt32 Msg, Int32 wParam, Int32 lParam); However, I find when interfacing with interesting native interfaces, that have many pointer types, flattening everything into IntPtr makes the code very hard to read and removes the typical typechecking that a compiler can do. I've been using a pattern where I declare an unsafe struct to be an opaque pointer type. I can store this pointer type in a managed object, and the compiler can typecheck it form me. For example: class Foo { unsafe struct FOO {}; // opaque type unsafe FOO *my_foo; class if { [DllImport("mydll")] extern static unsafe FOO* get_foo(); [DllImport("mydll")] extern static unsafe void do_something_foo(FOO *foo); } public unsafe Foo() { this.my_foo = if.get_foo(); } public unsafe do_something_foo() { if.do_something_foo(this.my_foo); } While this example may not seem different than using IntPtr, when there are several pointer types moving between managed and native code, using these opaque pointer types for typechecking is a godsend. I have not run into any trouble using this technique in practice. However, I also have not seen an examples of anyone using this technique, and I wonder why. Is there any reason that the above code is invalid in the eyes of the .NET runtime? My main question is about how the .NET GC system treats "unsafe FOO *my_foo". Is this pointer something the GC system is going to try to trace, or is it simply going to ignore it? My hope is that because the underlying type is a struct, and it's declared unsafe, that the GC would ignore it. However, I don't know for sure. Thoughts?

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• Polymorphic Numerics on .Net and In C#

  - by Bent Rasmussen

  It's a real shame that in .Net there is no polymorphism for numbers, i.e. no INumeric interface that unifies the different kinds of numerical types such as bool, byte, uint, int, etc. In the extreme one would like a complete package of abstract algebra types. Joe Duffy has an article about the issue: http://www.bluebytesoftware.com/blog/CommentView,guid,14b37ade-3110-4596-9d6e-bacdcd75baa8.aspx How would you express this in C#, in order to retrofit it, without having influence over .Net or C#? I have one idea that involves first defining one or more abstract types (interfaces such as INumeric - or more abstract than that) and then defining structs that implement these and wrap types such as int while providing operations that return the new type (e.g. Integer32 : INumeric; where addition would be defined as public Integer32 Add(Integer32 other) { return Return(Value + other.Value); } I am somewhat afraid of the execution speed of this code but at least it is abstract. No operator overloading goodness... Any other ideas? .Net doesn't look like a viable long-term platform if it cannot have this kind of abstraction I think - and be efficient about it. Abstraction is reuse.

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• boost::lambda bind expressions can't get bind to string's empty() to work

  - by navigator

  Hi, I am trying to get the below code snippet to compile. But it fails with: error C2665: 'boost::lambda::function_adaptor::apply' : none of the 8 overloads could convert all the argument types. Sepcifying the return type when calling bind does not help. Any idea what I am doing wrong? Thanks. #include <boost/lambda/lambda.hpp> #include <boost/lambda/bind.hpp> #include <string> #include <map> int main() { namespace bl = boost::lambda; typedef std::map<int, std::string> types; types keys_and_values; keys_and_values[ 0 ] = "zero"; keys_and_values[ 1 ] = "one"; keys_and_values[ 2 ] = "Two"; std::for_each( keys_and_values.begin(), keys_and_values.end(), std::cout << bl::constant("Value empty?: ") << std::boolalpha << bl::bind(&std::string::empty, bl::bind(&types::value_type::second, _1)) << "\n"); return 0; }

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• database design suggestion needed

  - by JMSA

  I need to design a table for daily sales of pharmaceutical products. There are hundreds of types of products available {Name, code}. Thousands of sales-persons are employed to sell those products{name, code}. They collect products from different depots{name, code}. They work in different Areas - Zones - Markets - Outlets, etc. {All have names and codes} Each product has various types of prices {Production Price, Trade Price, Business Price, Discount Price, etc.}. And, sales-persons are free to choose from those combination to estimate the sales price. The problem is, daily sales requires huge amount of data-entry. Within couple of years there may be gigabytes of data (if not terabytes). If I need to show daily, weekly, monthly, quarterly and yearly sales reports there will be various types of sql queries I shall need. This is my initial design: Product {ID, Code, Name, IsActive} ProductXYZPriceHistory {ID, ProductID, Date, EffectDate, Price, IsCurrent} SalesPerson {ID, Code, Name, JoinDate, and so on..., IsActive} SalesPersonSalesAraeaHistory {ID, SalesPersonID, SalesAreaID, IsCurrent} Depot {ID, Code, Name, IsActive} Outlet {ID, Code, Name, AreaID, IsActive} AreaHierarchy {ID, Code, Name, PrentID, AreaLevel, IsActive} DailySales {ID, ProductID, SalesPersonID, OutletID, Date, PriceID, SalesPrice, Discount, etc...} Now, apart from indexing, how can I normalize my DailySales table to have a fine grained design that I shall not need to change for years to come? Please show me a sample design of only the DailySales data-entry table (from which all types of reports would be queried) on the basis of above information. I don't need a detailed design advice. I just need an advice regarding only the DailySales table. Is there any way to break this particular table to achieve granularity?

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• Why linking doesn't work in my Xtext-based DSL?

  - by reprogrammer

  The following is the Xtext grammar for my DSL. Model: variableTypes=VariableTypes predicateTypes=PredicateTypes variableDeclarations= VariableDeclarations rules=Rules; VariableType: name=ID; VariableTypes: 'var types' (variableTypes+=VariableType)+; PredicateTypes: 'predicate types' (predicateTypes+=PredicateType)+; PredicateType: name=ID '(' (variableTypes+=[VariableType|ID])+ ')'; VariableDeclarations: 'vars' (variableDeclarations+=VariableDeclaration)+; VariableDeclaration: name=ID ':' type=[VariableType|ID]; Rules: 'rules' (rules+=Rule)+; Rule: head=Head ':-' body=Body; Head: predicate=Predicate; Body: (predicates+=Predicate)+; Predicate: predicateType=[PredicateType|ID] '(' (terms+=Term)+ ')'; Term: variable=Variable; Variable: variableDeclaration=[VariableDeclaration|ID]; terminal WS: (' ' | '\t' | '\r' | '\n' | ',')+; And, the following is a program in the above DSL. var types Node predicate types Edge(Node, Node) Path(Node, Node) vars x : Node y : Node z : Node rules Path(x, y) :- Edge(x, y) Path(x, y) :- Path(x, z) Path(z, y) When I used the generated Switch class to traverse the EMF object model corresponding to the above program, I realized that the nodes are not linked together properly. For example, the getPredicateType() method on a Predicate node returns null. Having read the Xtext user's guide, my impression is that the Xtext default linking semantics should work for my DSL. But, for some reason, the AST nodes of my DSL don't get linked together properly. Can anyone help me in diagnosing this problem?

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• How to find the first declaring method for a reference method

  - by Oliver Gierke

  Suppose you have a generic interface and an implementation: public interface MyInterface<T> { void foo(T param); } public class MyImplementation<T> implements MyInterface<T> { void foo(T param) { } } These two types are frework types. In the next step I want allow users to extend that interface as well as redeclare foo(T param) to maybe equip it with further annotations. public interface MyExtendedInterface extends MyInterface<Bar> { @Override void foo(Bar param); // Further declared methods } I create an AOP proxy for the extended interface and intercept especially the calls to furtherly declared methods. As foo(…) is no redeclared in MyExtendedInterface I cannot execute it by simply invoking MethodInvocation.proceed() as the instance of MyImplementation only implements MyInterface.foo(…) and not MyExtendedInterface.foo(…). So is there a way to get access to the method that declared a method initially? Regarding this example is there a way to find out that foo(Bar param) was declared in MyInterface originally and get access to the accoriding Method instance? I already tried to scan base class methods to match by name and parameter types but that doesn't work out as generics pop in and MyImplementation.getMethod("foo", Bar.class) obviously throws a NoSuchMethodException. I already know that MyExtendedInterface types MyInterface to Bar. So If I could create some kind of "typed view" on MyImplementation my math algorithm could work out actually.

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• Unity Configuration and Same Assembly

  - by tyndall

  I'm currently getting an error trying to resolve my IDataAccess class. The value of the property 'type' cannot be parsed. The error is: Could not load file or assembly 'TestProject' or one of its dependencies. The system cannot find the file specified. (C:\Source\TestIoC\src\TestIoC\TestProject\bin\Debug\TestProject.vshost.exe.config line 14) This is inside a WPF Application project. What is the correct syntax to refer to the Assembly you are currently in? is there a way to do this? I know in a larger solution I would be pulling Types from seperate assemblies so this might not be an issue. But what is the right way to do this for a small self-contained test project. Note: I'm only interested in doing the XML config at this time, not the C# (in code) config. UPDATE: see all comments My XML config: <configuration> <configSections> <section name="unity" type="Microsoft.Practices.Unity.Configuration.UnityConfigurationSection, Microsoft.Practices.Unity.Configuration" /> </configSections> <unity> <typeAliases> <!-- Lifetime manager types --> <typeAlias alias="singleton" type="Microsoft.Practices.Unity.ContainerControlledLifetimeManager, Microsoft.Practices.Unity" /> <typeAlias alias="external" type="Microsoft.Practices.Unity.ExternallyControlledLifetimeManager, Microsoft.Practices.Unity" /> <typeAlias alias="IDataAccess" type="TestProject.IDataAccess, TestProject" /> <typeAlias alias="DataAccess" type="TestProject.DataAccess, TestProject" /> </typeAliases> <containers> <container name="Services"> <types> <type type="IDataAccess" mapTo="DataAccess" /> </types> </container> </containers> </unity> </configuration>

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• Mysql select - improve performance

  - by realshadow

  Hey, I am working on an e-shop which sells products only via loans. I display 10 products per page in any category, each product has 3 different price tags - 3 different loan types. Everything went pretty well during testing time, query execution time was perfect, but today when transfered the changes to the production server, the site "collapsed" in about 2 minutes. The query that is used to select loan types sometimes hangs for ~10 seconds and it happens frequently and thus it cant keep up and its hella slow. The table that is used to store the data has approximately 2 milion records and each select looks like this: SELECT * FROM products_loans WHERE KOD IN("X17/Q30-10", "X17/12", "X17/5-24") AND 369.27 BETWEEN CENA_OD AND CENA_DO; 3 loan types and the price that needs to be in range between CENA_OD and CENA_DO, thus 3 rows are returned. But since I need to display 10 products per page, I need to run it trough a modified select using OR, since I didnt find any other solution to this. I have asked about it here, but got no answer. As mentioned in the referencing post, this has to be done separately since there is no column that could be used in a join (except of course price and code, but that ended very, very badly). Here is the show create table, kod and CENA_OD/CENA_DO very indexed via INDEX. CREATE TABLE `products_loans` ( `KOEF_ID` bigint(20) NOT NULL, `KOD` varchar(30) NOT NULL, `AKONTACIA` int(11) NOT NULL, `POCET_SPLATOK` int(11) NOT NULL, `koeficient` decimal(10,2) NOT NULL default '0.00', `CENA_OD` decimal(10,2) default NULL, `CENA_DO` decimal(10,2) default NULL, `PREDAJNA_CENA` decimal(10,2) default NULL, `AKONTACIA_SUMA` decimal(10,2) default NULL, `TYP_VYHODY` varchar(4) default NULL, `stage` smallint(6) NOT NULL default '1', PRIMARY KEY (`KOEF_ID`), KEY `CENA_OD` (`CENA_OD`), KEY `CENA_DO` (`CENA_DO`), KEY `KOD` (`KOD`), KEY `stage` (`stage`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8 And also selecting all loan types and later filtering them trough php doesnt work good, since each type has over 50k records and the select takes too much time as well... Any ides about improving the speed are appreciated.

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• Why does Microsoft advise against readonly fields with mutable values?

  - by Weeble

  In the Design Guidelines for Developing Class Libraries, Microsoft say: Do not assign instances of mutable types to read-only fields. The objects created using a mutable type can be modified after they are created. For example, arrays and most collections are mutable types while Int32, Uri, and String are immutable types. For fields that hold a mutable reference type, the read-only modifier prevents the field value from being overwritten but does not protect the mutable type from modification. This simply restates the behaviour of readonly without explaining why it's bad to use readonly. The implication appears to be that many people do not understand what "readonly" does and will wrongly expect readonly fields to be deeply immutable. In effect it advises using "readonly" as code documentation indicating deep immutability - despite the fact that the compiler has no way to enforce this - and disallows its use for its normal function: to ensure that the value of the field doesn't change after the object has been constructed. I feel uneasy with this recommendation to use "readonly" to indicate something other than its normal meaning understood by the compiler. I feel that it encourages people to misunderstand the meaning of "readonly", and furthermore to expect it to mean something that the author of the code might not intend. I feel that it precludes using it in places it could be useful - e.g. to show that some relationship between two mutable objects remains unchanged for the lifetime of one of those objects. The notion of assuming that readers do not understand the meaning of "readonly" also appears to be in contradiction to other advice from Microsoft, such as FxCop's "Do not initialize unnecessarily" rule, which assumes readers of your code to be experts in the language and should know that (for example) bool fields are automatically initialised to false, and stops you from providing the redundancy that shows "yes, this has been consciously set to false; I didn't just forget to initialize it". So, first and foremost, why do Microsoft advise against use of readonly for references to mutable types? I'd also be interested to know: Do you follow this Design Guideline in all your code? What do you expect when you see "readonly" in a piece of code you didn't write?

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• Are Dynamic Prepared Statements Bad? (with php + mysqli)

  - by John

  I like the flexibility of Dynamic SQL and I like the security + improved performance of Prepared Statements. So what I really want is Dynamic Prepared Statements, which is troublesome to make because bind_param and bind_result accept "fixed" number of arguments. So I made use of an eval() statement to get around this problem. But I get the feeling this is a bad idea. Here's example code of what I mean // array of WHERE conditions $param = array('customer_id'=>1, 'qty'=>'2'); $stmt = $mysqli->stmt_init(); $types = ''; $bindParam = array(); $where = ''; $count = 0; // build the dynamic sql and param bind conditions foreach($param as $key=>$val) { $types .= 'i'; $bindParam[] = '$p'.$count.'=$param["'.$key.'"]'; $where .= "$key = ? AND "; $count++; } // prepare the query -- SELECT * FROM t1 WHERE customer_id = ? AND qty = ? $sql = "SELECT * FROM t1 WHERE ".substr($where, 0, strlen($where)-4); $stmt->prepare($sql); // assemble the bind_param command $command = '$stmt->bind_param($types, '.implode(', ', $bindParam).');'; // evaluate the command -- $stmt->bind_param($types,$p0=$param["customer_id"],$p1=$param["qty"]); eval($command); Is that last eval() statement a bad idea? I tried to avoid code injection by encapsulating values behind the variable name $param. Does anyone have an opinion or other suggestions? Are there issues I need to be aware of?

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• What's the recommended implementation for hashing OLE Variants?

  - by Barry Kelly

  OLE Variants, as used by older versions of Visual Basic and pervasively in COM Automation, can store lots of different types: basic types like integers and floats, more complicated types like strings and arrays, and all the way up to IDispatch implementations and pointers in the form of ByRef variants. Variants are also weakly typed: they convert the value to another type without warning depending on which operator you apply and what the current types are of the values passed to the operator. For example, comparing two variants, one containing the integer 1 and another containing the string "1", for equality will return True. So assuming that I'm working with variants at the underlying data level (e.g. VARIANT in C++ or TVarData in Delphi - i.e. the big union of different possible values), how should I hash variants consistently so that they obey the right rules? Rules: Variants that hash unequally should compare as unequal, both in sorting and direct equality Variants that compare as equal for both sorting and direct equality should hash as equal It's OK if I have to use different sorting and direct comparison rules in order to make the hashing fit. The way I'm currently working is I'm normalizing the variants to strings (if they fit), and treating them as strings, otherwise I'm working with the variant data as if it was an opaque blob, and hashing and comparing its raw bytes. That has some limitations, of course: numbers 1..10 sort as [1, 10, 2, ... 9] etc. This is mildly annoying, but it is consistent and it is very little work. However, I do wonder if there is an accepted practice for this problem.

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• What corresponds to the Unity 'registration name' in the unity configuration section?

  - by unanswered

  When registering and resolving types in a Unity Container using code you can use 'Registration Names' to disambiguate your references that derive from an interface or base class hierarchy. The 'registration name' text would be provided as a parameter to the register and resolve methods: myContainer.RegisterType<IMyService, CustomerService>("Customers"); and MyServiceBase result = myContainer.Resolve<MyServiceBase>("Customers"); However when I register types in the configuration files I do not see where the 'registration name' can be assigned I register an Interface: <typeAlias alias="IEnlistmentNotification" type="System.Transactions.IEnlistmentNotification, System.Transactions, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" /> Then two types that I happen to know implement that interface: <typeAlias alias="PlaylistManager" type="Sample.Dailies.Grid.Workers.PlaylistManager, Sample.Dailies.Grid.Workers, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null" /> <typeAlias alias="FlexAleManager" type="Sample.Dailies.Grid.Workers.FlexAleManager, Sample.Dailies.Grid.Workers, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null" /> Then I provide mappings between the interface and the two types: <type type="IEnlistmentNotification" mapTo="FlexAleManager"><lifetime type="singleton"/></type> <type type="IEnlistmentNotification" mapTo="PlaylistManager"><lifetime type="singleton"/></type> That seems to correspond to this code: myContainer.RegisterType<IEnlistmentNotification, FlexAleManager>(); myContainer.RegisterType<IEnlistmentNotification, PlaylistManager>(); but clearly what I need is a disambiguating config entry that corresponds to this code: myContainer.RegisterType<IEnlistmentNotification, FlexAleManager>("Flex"); myContainer.RegisterType<IEnlistmentNotification, PlaylistManager>("Play"); Then when I get into my code I could do this: IEnlistmentNotification flex = myContainer.Resolve<IEnlistmentNotification>("Flex"); IEnlistmentNotification play = myContainer.Resolve<IEnlistmentNotification>("Play"); See what I mean? Thanks, Kimball

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• reshaping a data frame into long format in R

  - by user1773115

  I'm struggling with a reshape in R. I have 2 types of error (err and rel_err) that have been calculated for 3 different models. This gives me a total of 6 error variables (i.e. err_1, err_2, err_3, rel_err_1, rel_err_2, and rel_err_3). For each of these types of error I have 3 different types of predivtive validity tests (ie random holdouts, backcast, forecast). I would like to make my data set long so I keep the 4 types of test long while also making the two error measurements long. So in the end I will have one variable called err and one called rel_err as well as an id variable for what model the error corresponds to (1,2,or 3) Here is my data right now: iter err_1 rel_err_1 err_2 rel_err_2 err_3 rel_err_3 test_type 1 -0.09385732 -0.2235443 -0.1216982 -0.2898543 -0.1058366 -0.2520759 random 1 0.16141630 0.8575728 0.1418732 0.7537442 0.1584816 0.8419816 back 1 0.16376930 0.8700738 0.1431505 0.7605302 0.1596502 0.8481901 front 1 0.14345986 0.6765194 0.1213689 0.5723444 0.1374676 0.6482615 random 1 0.15890059 0.7435382 0.1589823 0.7439204 0.1608709 0.7527580 back 1 0.14412360 0.6743928 0.1442039 0.6747684 0.1463520 0.6848202 front and here is what I would like it to look like: iter model err rel_err test_type 1 1 -0.09385732 (#'s) random 1 2 -0.1216982 (#'s) random 1 3 -0.1216982 (#'s) random and on... I've tried playing around with the syntax but can't quite figure out what to put for the time.varying argument Thanks very much for any help you can offer.

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• Consume WCF Service InProcess using Agatha and WCF

  - by REA_ANDREW

  I have been looking into this lately for a specific reason.  Some integration tests I want to write I want to control the types of instances which are used inside the service layer but I want that control from the test class instance.  One of the problems with just referencing the service is that a lot of the time this will by default be done inside a different process.  I am using StructureMap as my DI of choice and one of the tools which I am using inline with RhinoMocks is StructureMap.AutoMocking.  With StructureMap the main entry point is the ObjectFactory.  This will be process specific so if I decide that the I want a certain instance of a type to be used inside the ServiceLayer I cannot configure the ObjectFactory from my test class as that will only apply to the process which it belongs to. This is were I started thinking about two things: Running a WCF in process Being able to share mocked instances across processes A colleague in work pointed me to a project which is for the latter but I thought that it would be a better solution if I could run the WCF Service in process.  One of the projects which I use when I think about WCF Services is AGATHA, and the one which I have to used to try and get my head around doing this. Another asset I have is a book called Programming WCF Services by Juval Lowy and if you have not heard of it or read it I would definately recommend it.  One of the many topics that is inside this book is the type of configuration you need to communicate with a service in the same process, and it turns out to be quite simple from a config point of view. <system.serviceModel> <services> <service name="Agatha.ServiceLayer.WCF.WcfRequestProcessor"> <endpoint address ="net.pipe://localhost/MyPipe" binding="netNamedPipeBinding" contract="Agatha.Common.WCF.IWcfRequestProcessor"/> </service> </services> <client> <endpoint name="MyEndpoint" address="net.pipe://localhost/MyPipe" binding="netNamedPipeBinding" contract="Agatha.Common.WCF.IWcfRequestProcessor"/> </client> </system.serviceModel>   You can see here that I am referencing the Agatha object and contract here, but also that my binding and the address is something called Named Pipes.  THis is sort of the “Magic” which makes it happen in the same process. Next I need to open the service prior to calling the methods on a proxy which I also need.  My initial attempt at the proxy did not use any Agatha specific coding and one of the pains I found was that you obviously need to give your proxy the known types which the serializer can be aware of.  So we need to add to the known types of the proxy programmatically.  I came across the following blog post which showed me how easy it was http://bloggingabout.net/blogs/vagif/archive/2009/05/18/how-to-programmatically-define-known-types-in-wcf.aspx. First Pass So with this in mind, and inside a console app this was my first pass at consuming a service in process.  First here is the proxy which I made making use of the Agatha IWcfRequestProcessor contract. public class InProcProxy : ClientBase<Agatha.Common.WCF.IWcfRequestProcessor>, Agatha.Common.WCF.IWcfRequestProcessor { public InProcProxy() { } public InProcProxy(string configurationName) : base(configurationName) { } public Agatha.Common.Response[] Process(params Agatha.Common.Request[] requests) { return Channel.Process(requests); } public void ProcessOneWayRequests(params Agatha.Common.OneWayRequest[] requests) { Channel.ProcessOneWayRequests(requests); } } So with the proxy in place I could then use this after opening the service so here is the code which I use inside the console app make the request. static void Main(string[] args) { ComponentRegistration.Register(); ServiceHost serviceHost = new ServiceHost(typeof(Agatha.ServiceLayer.WCF.WcfRequestProcessor)); serviceHost.Open(); Console.WriteLine("Service is running...."); using (var proxy = new InProcProxy()) { foreach (var operation in proxy.Endpoint.Contract.Operations) { foreach (var t in KnownTypeProvider.GetKnownTypes(null)) { operation.KnownTypes.Add(t); } } var request = new GetProductsRequest(); var responses = proxy.Process(new[] { request }); var response = (GetProductsResponse)responses[0]; Console.WriteLine("{0} Products have been retrieved", response.Products.Count); } serviceHost.Close(); Console.WriteLine("Finished"); Console.ReadLine(); } So what I used here is the KnownTypeProvider of Agatha to easily get all the types I need for the service/proxy and add them to the proxy.  My Request handler for this was just a test one which always returned 2 products. public class GetProductsHandler : RequestHandler<GetProductsRequest,GetProductsResponse> { public override Agatha.Common.Response Handle(GetProductsRequest request) { return new GetProductsResponse { Products = new List<ProductDto> { new ProductDto{}, new ProductDto{} } }; } } Second Pass Now after I did this I started reading up some more on some resources including more by Davy Brion and others on Agatha.  Now it turns out that the work I did above to create a derived class of the ClientBase implementing Agatha.Common.WCF.IWcfRequestProcessor was not necessary due to a nice class which is present inside the Agatha code base, RequestProcessorProxy which takes care of this for you! :-) So disregarding that class I made for the proxy and changing my code to use it I am now left with the following: static void Main(string[] args) { ComponentRegistration.Register(); ServiceHost serviceHost = new ServiceHost(typeof(Agatha.ServiceLayer.WCF.WcfRequestProcessor)); serviceHost.Open(); Console.WriteLine("Service is running...."); using (var proxy = new RequestProcessorProxy()) { var request = new GetProductsRequest(); var responses = proxy.Process(new[] { request }); var response = (GetProductsResponse)responses[0]; Console.WriteLine("{0} Products have been retrieved", response.Products.Count); } serviceHost.Close(); Console.WriteLine("Finished"); Console.ReadLine(); }   Cheers for now, Andy References Agatha WCF InProcess Without WCF StructureMap.AutoMocking Cross Process Mocking Agatha Programming WCF Services by Juval Lowy

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