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• SQL INSTR() using CSV. Need exact match rather than part

  - by Alastair Pitts

  This is a follow up issue relating to the answer for http://stackoverflow.com/questions/2445029/sql-placeholder-in-where-in-issue-inserted-strings-fail Quick background: We have a SQL query that uses a placeholder value to accept a string, which represents a unique tag/id. Usually, this is only a single tag, but we needed the ability to use a csv string for multiple tags, returning a combined result. In the answer we received from the vendor, they suggested the use of the INSTR function, ala: select * from pitotal where tag IN (SELECT tag from pipoint WHERE INSTR(?, tag) <> 0) and time between 'y' and 't' This works perfectly well 99% of the time, the issue is when the tag is also a subset of 2 parts of the CSV string. Eg the placeholder value is: 'northdom,southdom,eastdom,westdom' and possible tags include: north or northdom What happens, as north is a subset of northdom, is that the two tags are return instead of just northdom, which is actually what we want. I'm not strong on SQL so I couldn't work out how to set it as exact, or split the csv string, so help would be appreciated. Is there a way to split the csv string or make it look for an exact match?

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• Convert function to read from string instead of file in C

  - by Dusty

  I've been tasked with updating a function which currently reads in a configuration file from disk and populates a structure: static int LoadFromFile(FILE *Stream, ConfigStructure *cs) { int tempInt; ... if ( fscanf( Stream, "Version: %d\n",&tempInt) != 1 ) { printf("Unable to read version number\n"); return 0; } cs->Version = tempInt; ... } to one which allows us to bypass writing the configuration to disk and instead pass it directly in memory, roughly equivalent to this: static int LoadFromString(char *Stream, ConfigStructure *cs) A few things to note: The current LoadFromFile function is incredibly dense and complex, reading dozens of versions of the config file in a backward compatible manner, which makes duplication of the overall logic quite a pain. The functions that generate the config file and those that read it originate in totally different parts of the old system and therefore don't share any data structures so I can't pass those directly. I could potentially write a wrapper, but again, it would need to handle any structure passed in in a backwards compatible manner. I'm tempted to just pass the file as is in as a string (as in the prototype above) and convert all the fscanf's to sscanf's but then I have to handle incrementing the pointer along (and potentially dealing with buffer overrun errors) manually. This has to remain in C, so no C++ functionality like streams can help here Am I missing a better option? Is there some way to create a FILE * that actually just points to a location in memory instead of on disk? Any pointers, suggestions or other help is greatly appreciated.

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• Need Help with SQL Subquery

  - by Pete Augello

  Hey: I am trying to write a query that will return all orders that only have a Subscription included. It is easy enough to write a query that includes all Orders with Subscriptions, another that includes all orders without a Subscription and then compare them with an unmatched query. But I don't want to have to store Queries in my Access database, I prefer to have it all in my ASP code, and I can't get this to work with just one complex query. Here are samples of what works if I store them: Query1 SELECT tblOrders.OrderID, tblOrderItems.ProductID FROM tblOrders INNER JOIN tblOrderItems ON tblOrders.OrderID = tblOrderItems.OrderID WHERE ((Not ((tblOrderItems.ProductID)=12 And (tblOrderItems.ProductID)<=15))); Query2 SELECT tblOrders.OrderID, tblOrderItems.ProductID FROM tblOrders INNER JOIN tblOrderItems ON tblOrders.OrderID = tblOrderItems.OrderID WHERE ((((tblOrderItems.ProductID)=12 And (tblOrderItems.ProductID)<=15))); Query3 SELECT Query2.OrderID, Query2.ProductID FROM Query2 LEFT JOIN Query1 ON Query2.OrderID = Query1.OrderID WHERE (((Query1.OrderID) Is Null)); So, my question is 'how do I write Query3 so that it doesn't refer to Query1 or Query2?' or, am I missing some other way do do this? Thanks, Pete [email protected]

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• How to implement properly plugins in C#?

  - by MartyIX

  I'm trying to add plugins to my game and what I'm trying to implement is this: Plugins will be either mine or 3rd party's so I would like a solution where crashing of the plugin would not mean crashing of the main application. Methods of plugins are called very often (for example because of drawing of game objects). What I've found so far: 1) http://www.codeproject.com/KB/cs/pluginsincsharp.aspx - simple concept that seems like it should work nicely. Since plugins are used in my game for every round I would suffice to add the Restart() method and if a plugin is no longer needed Unload() method + GC should take care of that. 2) http://mef.codeplex.com/Wikipage - Managed Extensibility Framework - my program should work on .NET 3.5 and I don't want to add any other framework separately I want to write my plugin system myself. Therefore this solution is out of question. 3) Microsoft provides: http://msdn.microsoft.com/en-us/library/system.addin.aspx but according to a few articles I've read it is very complex. 4) Different AppDomains for plugins. According to Marc Gravell ( http://stackoverflow.com/questions/665668/usage-of-appdomain-in-c ) different AppDomains allow isolation. Unloading of plugins would be easy. What would the performance load be? I need to call methods of plugins very often (to draw objects for example). Using Application Domains - http://msdn.microsoft.com/en-us/library/yb506139.aspx A few tutorials on java2s.com Could you please comment on my findings? New approaches are also welcomed! Thanks!

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• CLR Stored Procedures

  - by Paul Hatcherian

  In an ASP.NET application, I have a small number of fairly complex, frequently used operations to execute against a database. In these operations, one or more of several tables needs updates or inserts based a logical evaluation of both input parameters and values of certain tables. I've maintained a separation of logic and data access, so the operation currently looks like this: Request received from client Business layer invokes data layer to retrieve data from database Business layer processes result and determines which operation to execute Business layer invokes appropriate data operation Response sent to client As you can see, the client is kept waiting while two separate requests are made to the database. In searching for a solution to this, I've found CLR Stored Procedures, but I'm not sure if I have the right idea about what they are useful for. I have written a replacement for the code above which especially places steps 2-4 in a CLR SP. My understanding is that the SP will be executed locally by SQL Server and result in only one call being made to the server. My initial benchmark tests show this is actually orders of magnitude slower than my original code, but I attribute that recompilation of the code I have not worked out yet and/or some flaw in my environment. My question is basically, is this the intended use of CLR SPs or am I missing something? I realize this is a bit of a compromise structurally, so if there's a better way to do it I'd love to hear it.

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• Connect two client sockets

  - by Hernán Eche

  Good morning, let's say Java has two kind of sockets... server sockets "ServerSocket" client sockets or just "Socket" ////so Simple ! Imagine the situation of two processes: X Client <-- Y Server The server process Y : has a "ServerSocket", that is listening to a TCP port The client process X : send a connection request through a -client type- "Socket" X ////so Simple ! then the accept() method (in server Y) returns a new client type "Socket", when it occurs, great the two Sockets get "interconected", so the -client socket- in client process, is connected with the -client socket- in the server process then (reading/writing in socket X is like reading/writing in socket Y, and viceversa. ) TWO CLIENT SOCKETS GET INTERCONECTED!! ////so Simple ! BUT... (there is always a But..) What if I create the two CLIENT sockets in same process, and I want to get them "interconected" ? ////mmm Complex =(... even posible? Let's say how to have TWO CLIENT SOCKETS GET INTERCONECTED WITHOUT using an intermediate ServerSocket ? I 've solved it.. by creating two threads for continuously reading A and writing B, and other for reading B and writng A... but I think could be a better way..(or should!) (Those world-energy-consuming threads are not necessary with the client-server aproach) Any help or advice would be appreciated!! Thanks

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• Take most significant 8 bytes of the MD5 hash of a string as a long (in Ruby)

  - by Nate Murray

  Hey Friends, I'm trying to implement a java "hash" function in ruby. Here's the java side: import java.nio.charset.Charset; import java.security.MessageDigest; /** * @return most significant 8 bytes of the MD5 hash of the string, as a long */ protected long hash(String value) { byte[] md5hash; md5hash = md5Digest.digest(value.getBytes(Charset.forName("UTF8"))); long hash = 0L; for (int i = 0; i < 8; i++) { hash = hash << 8 | md5hash[i] & 0x00000000000000FFL; } return hash; } So far, my best guess in ruby is: # WRONG - doesn't work properly. #!/usr/bin/env ruby -wKU require 'digest/md5' require 'pp' md5hash = Digest::MD5.hexdigest("0").unpack("U*") pp md5hash hash = 0 0.upto(7) do |i| hash = hash << 8 | md5hash[i] & 0x00000000000000FF end pp hash Problem is, this ruby code doesn't match the java output. For reference, the above java code given these strings returns the corresponding long: "00038c53790ecedfeb2f83102e9115a522475d73" => -2059313900129568948 "0" => -3473083983811222033 "001211e8befc8ac22dd265ecaa77f8c227d0007f" => 3234260774580957018 Thoughts: I'm having problems getting the UTF8 bytes from the ruby string In ruby I'm using hexdigest, I suspect I should be using just digest instead The java code is taking the md5 of the UTF8 bytes whereas my ruby code is taking the bytes of the md5 (as hex) Any suggestions on how to get the exact same output in ruby?

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• Doctesting functions that receive and display user input - Python (tearing my hair out)

  - by GlenCrawford

  Howdy! I am currently writing a small application with Python (3.1), and like a good little boy, I am doctesting as I go. However, I've come across a method that I can't seem to doctest. It contains an input(), an because of that, I'm not entirely sure what to place in the "expecting" portion of the doctest. Example code to illustrate my problem follows: """ >>> getFiveNums() Howdy. Please enter five numbers, hit <enter> after each one Please type in a number: Please type in a number: Please type in a number: Please type in a number: Please type in a number: """ import doctest numbers = list() # stores 5 user-entered numbers (strings, for now) in a list def getFiveNums(): print("Howdy. Please enter five numbers, hit <enter> after each one") for i in range(5): newNum = input("Please type in a number:") numbers.append(newNum) print("Here are your numbers: ", numbers) if __name__ == "__main__": doctest.testmod(verbose=True) When running the doctests, the program stops executing immediately after printing the "Expecting" section, waits for me to enter five numbers one after another (without prompts), and then continues. As shown below: I don't know what, if anything, I can place in the Expecting section of my doctest to be able to test a method that receives and then displays user input. So my question (finally) is, is this function doctestable?

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• Design: Website calling a webservice on the same machine

  - by Chris L

  More of a design/conceptual question. At work the decision was made to have our data access layer be called through webservices. So our website would call the webservices for any/all data to and from the database. Both the website & the webservices will be on the same machine(so no trip across the wire), but the database is on a separate machine(so that would require a trip across the wire regardless). This is all in-house, the website, webservice, and database are all within the same company(AFAIK, the webservices won't be reused by another other party). To the best of my knowledge: the website will open a port to the webservices, and the webservices will in turn open another port and go across the wire to the database server to get/submit the data. The trip across the wire can't be avoided, but I'm concerned about the webservices standing in the middle. I do agree there needs to be distinct layers between the functionality(such as business layer, data access layer, etc...), but this seems overly complex to me. I'm also sensing there will be some performance problems down the line. Seems to me it would be better to have the (DAL)assemblies referenced directly within the solution, thus negating the first port to port connection. Any thoughts(or links) both for and against this idea would be appreciated P.S. We're a .NET shop(migrating from vb to C# 3.5)

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• Synchronizing a collection of wrapped objects with a collection of unwrapped objects

  - by Kenneth Cochran

  I have two classes: Employee and EmployeeGridViewAdapter. Employee is composed of several complex types. EmployeeGridViewAdapter wraps a single Employee and exposes its members as a flattened set of system types so a DataGridView can handle displaying, editing, etc. I'm using VS's builtin support for turning a POCO into a data source, which I then attach to a BindingSource object. When I attach the DataGridView to the BindingSource it creates the expected columns and at runtime I can perform the expected CRUD operations. All is good so far. The problem is the collection of adapters and the collection of employees aren't being synchronized. So all the employees I create an runtime never get persisted. Here's a snippet of the code that generates the collection of EmployeeGridViewAdapter's: var employeeCollection = new List<EmployeeGridViewAdapter>(); foreach (var employee in this.employees) { employeeCollection.Add(new EmployeeGridViewAdapter(employee)); } this.view.Employees = employeeCollection; Pretty straight forward but I can't figure out how to synchronize changes back to the original collection. I imagine edits are already handled because both collections reference the same objects but creating new employees and deleting employees aren't happening so I can't be sure.

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• C# .net Deserialization I get an exception.

  - by starz26

  namespace N1 { public class InputEntry { //FieldName is a class tht is generated from an XSD which has complex type Name and value private FieldName[] name; public FieldName[] Name { get { return this.Name; } set { this.Name = value; } } } public class B { public void Method1() { InputEntry inputEntry = new InputEntry(); inputEntry.Name = "abc"; } private void Method2(InputEntry inputEntry) { System.Xml.Serialization.XmlSerializer serializer = new System.Xml.Serialization.XmlSerializer(typeof(InputEntry)); System.IO.StringWriter inputStr = new System.IO.StringWriter(CultureInfo.InvariantCulture); serializer.Serialize(inputStr, inputEntry); string ipEntry = inputStr.ToString(); Method3(ipEntry); } private void Method3(string ipEntry) { System.Xml.Serialization.XmlSerializer serializer = new System.Xml.Serialization.XmlSerializer(typeof(InputEntry)); System.IO.StringReader inputStr = new System.IO.StringReader(ipEntry); InputEntry inputEntry = (InputEntry)serializer.Deserialize(inputStr); } } } I get an exception when deserialising the follwing data(when a client configues data as <FieldName>PRINTLINE00</FieldName> <FieldValue>DENIAL STATE</FieldValue> ) Exception is: Message: There is an error in XML document (6, 22). String: <?xml version="1.0" encoding="utf-16"?> <InputEntry xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xmlns:xsd="http://www.w3.org/2001/XMLSchema"> <Fields> <Field> <FieldName>PRINTLINE00</FieldName> <FieldValue>&#x1B;DENIAL STATE 217</FieldValue> </Field> </InputEntry>

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• Validating User Input? C#

  - by Alex

  Hi, in an assignment, I have designed a input validation loop in C#, and I would like it to be able to check for the correct input format. I'm not for sure, but I think my designed loop is not checking the type of input, just what char is entered. I know I could use a try-catch block, but shouldn't you only use exceptions for exceptional situations? This is not an exceptional situation, because I expect that the user would enter an incorrect value. Input validation is not part of my assignment, so the loop is in a homework assignment, but is not part of the homework assignment. Question: Is there a way I could redesign this loop so that it checks for valid input type as well? Code: do { Console.Write("Do you wish to enter another complex number?: (Y or N)"); response = char.Parse(Console.ReadLine()); response = char.ToUpper(response); if (response != 'Y' && response != 'N') Console.WriteLine("You must respond Y or N!"); } while (response != 'Y' && response != 'N'); Thanks!!

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• Extending ASP.NET role providers

  - by Quick Joe Smith

  Because the RoleProvider interface seems to treat roles as nothing more than simple strings, I'm wondering if there is any non-hacky way to apply an optional value for a role on a per-user basis. Our current login management system implements roles as key-value pairs, where the value part is optional and usually used to clarify or limit the permissions granted by a role. For example, a role 'editor' might contain a user 'barry', but for 'barry' it will have an optional value 'raptors', which the system would interpret to mean that Barry can only edit articles filed under the 'raptors' category. I have seen elsewhere a suggestion to simply create additional delimited roles, such as 'editor.raptors' or somesuch. That's not really going to be ideal because it would bloat the number of roles greatly, and I can tell it's going to be a very hard sell to replace our current implementation (which is also very less than ideal, but has the advantage of being custom made to work with our user database). I can tell already that the concatenation method mentioned above is going to involve a lot of tedious string-splitting and partial matching. Is there a better way?

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• IValueConverter from string

  - by Aleksandar Toplek

  I have an Enum that needs to be shown in ComboBox. I have managed to get enum values to combobox using ItemsSource and I'm trying to localize them. I thought that that could be done using value converter but as my enum values are already strings compiler throws error that IValueConverter can't take string as input. I'm not aware of any other way to convert them to other string value. Is there some other way to do that (not the localization but conversion)? I'm using this marku extension to get enum values [MarkupExtensionReturnType(typeof (IEnumerable))] public class EnumValuesExtension : MarkupExtension { public EnumValuesExtension() {} public EnumValuesExtension(Type enumType) { this.EnumType = enumType; } [ConstructorArgument("enumType")] public Type EnumType { get; set; } public override object ProvideValue(IServiceProvider serviceProvider) { if (this.EnumType == null) throw new ArgumentException("The enum type is not set"); return Enum.GetValues(this.EnumType); } } and in Window.xaml <Converters:UserTypesToStringConverter x:Key="userTypeToStringConverter" /> .... <ComboBox ItemsSource="{Helpers:EnumValuesExtension Data:UserTypes}" Margin="2" Grid.Row="0" Grid.Column="1" SelectedIndex="0" TabIndex="1" IsTabStop="False"> <ComboBox.ItemTemplate> <DataTemplate DataType="{x:Type Data:UserTypes}"> <Label Content="{Binding Converter=userTypeToStringConverter}" /> </DataTemplate> </ComboBox.ItemTemplate> </ComboBox> And here is converter class, it's just a test class, no localization yet. public class UserTypesToStringConverter : IValueConverter { public object Convert(object value, Type targetType, object parameter, CultureInfo culture) { return (int) ((Data.UserTypes) value) == 0 ? "Fizicka osoba" : "Pravna osoba"; } public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture) { return default(Data.UserTypes); } }

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• Why is my multithreaded Java program not maxing out all my cores on my machine?

  - by James B

  Hi, I have a program that starts up and creates an in-memory data model and then creates a (command-line-specified) number of threads to run several string checking algorithms against an input set and that data model. The work is divided amongst the threads along the input set of strings, and then each thread iterates the same in-memory data model instance (which is never updated again, so there are no synchronization issues). I'm running this on a Windows 2003 64-bit server with 2 quadcore processors, and from looking at Windows task Manager they aren't being maxed-out, (nor are they looking like they are being particularly taxed) when I run with 10 threads. Is this normal behaviour? It appears that 7 threads all complete a similar amount of work in a similar amount of time, so would you recommend running with 7 threads instead? Should I run it with more threads?...Although I assume this could be detrimental as the JVM will do more context switching between the threads. Alternatively, should I run it with fewer threads? Alternatively, what would be the best tool I could use to measure this?...Would a profiling tool help me out here - indeed, is one of the several profilers better at detecting bottlenecks (assuming I have one here) than the rest? Note, the server is also running SQL Server 2005 (this may or may not be relevant), but nothing much is happening on that database when I am running my program. Note also, the threads are only doing string matching, they aren't doing any I/O or database work or anything else they may need to wait on. Thanks in advance, -James

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• What Language Feature Can You Just Not Live Without?

  - by akdom

  I always miss python's built-in doc strings when working in other languages. I know this may seem odd, but it allows me to cut down significantly on excess comments while still providing a clean description of my code and any interfaces therein. What Language Feature Can You Just Not Live Without? If someone were building a new language and they asked you what one feature they absolutely must include, what would it be? This is getting kind of long, so I figured I'd do my best to summarize: Paraphrased to be language agnostic. If you know of a language which uses something mentioned, please at it in the parenthesis to the right of the feature. And if you have a better format for this list, by all means try it out (if it doesn't seem to work, I'll just roll back). Regular Expressions ~ torial (Perl) Garbage Collection ~ SaaS Developer (Python, Perl, Ruby, Java, .NET) Anonymous Functions ~ Vinko Vrsalovic (Lisp, Python) Arithmetic Operators ~ Jeremy Ross (Python, Perl, Ruby, Java, C#, Visual Basic, C, C++, Pascal, Smalltalk, etc.) Exception Handling ~ torial (Python, Java, .NET) Pass By Reference ~ Chris (Python) Unified String Format WalloWizard (C#) Generics ~ torial (Python, Java, C#) Integrated Query Equivalent to LINQ ~ Vyrotek (C#) Namespacing ~ Garry Shutler () Short Circuit Logic ~ Adam Bellaire ()

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• Fast JSON serialization (and comparison with Pickle) for cluster computing in Python?

  - by user248237

  I have a set of data points, each described by a dictionary. The processing of each data point is independent and I submit each one as a separate job to a cluster. Each data point has a unique name, and my cluster submission wrapper simply calls a script that takes a data point's name and a file describing all the data points. That script then accesses the data point from the file and performs the computation. Since each job has to load the set of all points only to retrieve the point to be run, I wanted to optimize this step by serializing the file describing the set of points into an easily retrievable format. I tried using JSONpickle, using the following method, to serialize a dictionary describing all the data points to file: def json_serialize(obj, filename, use_jsonpickle=True): f = open(filename, 'w') if use_jsonpickle: import jsonpickle json_obj = jsonpickle.encode(obj) f.write(json_obj) else: simplejson.dump(obj, f, indent=1) f.close() The dictionary contains very simple objects (lists, strings, floats, etc.) and has a total of 54,000 keys. The json file is ~20 Megabytes in size. It takes ~20 seconds to load this file into memory, which seems very slow to me. I switched to using pickle with the same exact object, and found that it generates a file that's about 7.8 megabytes in size, and can be loaded in ~1-2 seconds. This is a significant improvement, but it still seems like loading of a small object (less than 100,000 entries) should be faster. Aside from that, pickle is not human readable, which was the big advantage of JSON for me. Is there a way to use JSON to get similar or better speed ups? If not, do you have other ideas on structuring this? (Is the right solution to simply "slice" the file describing each event into a separate file and pass that on to the script that runs a data point in a cluster job? It seems like that could lead to a proliferation of files). thanks.

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• Can someone look over the curriculum for this major & give me your thoughts? Computing & Security Te

  - by scottsharpejr

  My goal is to become a good web developer. I'm interested in learning how to build complex websites as well as how to write web applications. I want skills that will enable me to write apps for <--insert hottest web trend here-- (Facebook & iphone apps for example) This is one of my goals as far as Tech. is concerned. I'd also like to have a brod knowledge of different areas of IT. I'm looking into majoring in "Computing & Security Technology". The program is offered by Drexel in conjunction with my CC. It's a 4 year degree. Can someone take a look @ the pdf below. It outlines every course I must take. http://www.drexelatbcc.org/academics/PDF/CST_CT.pdf For degree requirments w/ links to course descriptiongs see drexel.edu/catalog/degree/ct.htm With electives I can go up to Web Development 4. Based on my goals of Web development & wanting a well rounding education in information technology, what do you think of the curriculum? How will I fare entering the job market with this degree? My goals here are a little different. I'd like to work for 2 to 3 companies over the course of 6-7 years. Working with and learning different areas of IT. I'd like to stay with a company an average of 2-3 years before moving on. My end goal is to go into business for myself (IT related). I appreciate any and all advice the community here can give me! :) Could someone also explain to me their interpretation of this major? thanks! P.S. I already know XHTML & CSS. I am just now starting to experiment with PHP.

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• How is the 'is' keyword implemented in Python?

  - by Srikanth

  ... the is keyword that can be used for equality in strings. >>> s = 'str' >>> s is 'str' True >>> s is 'st' False I tried both __is__() and __eq__() but they didn't work. >>> class MyString: ... def __init__(self): ... self.s = 'string' ... def __is__(self, s): ... return self.s == s ... >>> >>> >>> m = MyString() >>> m is 'ss' False >>> m is 'string' # <--- Expected to work False >>> >>> class MyString: ... def __init__(self): ... self.s = 'string' ... def __eq__(self, s): ... return self.s == s ... >>> >>> m = MyString() >>> m is 'ss' False >>> m is 'string' # <--- Expected to work, but again failed False >>> Thanks for your help!

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• How to best show progress info when using ADO.NET?

  - by Yadyn

  I want to show the user detailed progress information when performing potentially lengthy database operations. Specifically, when inserting/updating data that may be on the order of hundreds of KB or MB. Currently, I'm using in-memory DataTables and DataRows which are then synced with the database via TableAdapter.Update calls. This works fine and dandy, but the single call leaves little opportunity to glean any kind of progress info to show to the user. I have no idea how much data is passing through the network to the remote DB or its progress. Basically, all I know is when Update returns and it is assumed complete (barring any errors or exceptions). But this means all I can show is 0% and then a pause and then 100%. I can count the number of rows, even going so far to cound how many are actually Modified or Added, and I could even maybe calculate per DataRow its estimated size based on the datatype of each column, using sizeof for value types like int and checking length for things like strings or byte arrays. With that, I could probably determine, before updating, an estimated total transfer size, but I'm still stuck without any progress info once Update is called on the TableAdapter. Am I stuck just using an indeterminate progress bar or mouse waiting cursor? Would I need to radically change our data access layer to be able to hook into this kind of information? Even if I can't get it down to the precise KB transferred (like a web browser file download progress bar), could I at least know when each DataRow/DataTable finishes or something? How do you best show this kind of progress info using ADO.NET?

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• How can I find out what is stopping my object from disposing properly?

  - by SLC

  I have a rather large and complex game in C#, and in it are various monsters. The monsters are created in the game by a MonsterCreator, and each monster has various plugins that are loaded from external DLLs. When my monsters die, they call a method in the MonsterCreator, and the MonsterCreator removes them from the game map, removes them from its own internal list of monsters, and then finally calls the Dispose() method on the monster itself. The dispose method calls the dispose method of each plugin, then clears up any of its own code. This seems to work fine, with lots of monsters, but somewhere there is a bug that crops up after a while, where a monster dies, but it has already been removed - it seems the callback telling the MonsterCreator is being called over and over, when the monster should have been removed on the first call. The likely candidate is that some of the plugins for the monster register themselves with an Event that pulses them every X number of seconds so they can perform logic. Stepping through I can see that they are unregistering with the Event when they die, but something is getting through still and I don't know what it is. Do you have any advice for debugging the problem? I can't post code really because it's split across a ton of libraries and plugin dlls, so it's more a case of figuring out the best way to debug it. I threw an exception in code when the monster died callback method is thrown and the monster cannot be found on the map to be removed, so I have the misbehaviing Monster, is there a way I can see what is still linked to it?

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• A function where small changes in input always result in large changes in output

  - by snowlord

  I would like an algorithm for a function that takes n integers and returns one integer. For small changes in the input, the resulting integer should vary greatly. Even though I've taken a number of courses in math, I have not used that knowledge very much and now I need some help... An important property of this function should be that if it is used with coordinate pairs as input and the result is plotted (as a grayscale value for example) on an image, any repeating patterns should only be visible if the image is very big. I have experimented with various algorithms for pseudo-random numbers with little success and finally it struck me that md5 almost meets my criteria, except that it is not for numbers (at least not from what I know). That resulted in something like this Python prototype (for n = 2, it could easily be changed to take a list of integers of course): import hashlib def uniqnum(x, y): return int(hashlib.md5(str(x) + ',' + str(y)).hexdigest()[-6:], 16) But obviously it feels wrong to go over strings when both input and output are integers. What would be a good replacement for this implementation (in pseudo-code, python, or whatever language)?

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• How much business logic belongs in RIA services layer?

  - by jkohlhepp

  I have been experimenting recently with Silverlight, RIA Services, and Entity Framework using .NET 4.0. I'm trying to figure out if that stack makes sense for use in any of my upcoming projects. It certainly seems like these technologies can be very productive for developing applications, but I'm struggling to decide how an application on top of this stack should be architected. The main issue I have is that in most of the demos I've seen most of the business logic ends up as DataAnnotations and custom validations in the RIA Services domain service class. This seems inappropriate to me. I view the domain service as basically a glorified web service that happens to make it easy to push information to the client. But most of what I've seen seems to orient the domain service as the main source of business logic in the application. So, my questions: What is the best location for business logic (rules, validations, behaviors, authorization) in an application using this stack? Are there any guidelines published at an architectural level for using this stack? My questions pertain to large, complex, and long-lived applications. Obviously for an application of only a few screens this is less of a concern. Edit: Another thing I meant to mention is that obviously you can make the domain service class stupid, but then you lose a lot of the automagic entity information (e.g. validations) being pushed to the client. And then if you lose that is there any point to using RIA services?

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• How best to use XPath with very large XML files in .NET?

  - by glenatron

  I need to do some processing on fairly large XML files ( large here being potentially upwards of a gigabyte ) in C# including performing some complex xpath queries. The problem I have is that the standard way I would normally do this through the System.XML libraries likes to load the whole file into memory before it does anything with it, which can cause memory problems with files of this size. I don't need to be updating the files at all just reading them and querying the data contained in them. Some of the XPath queries are quite involved and go across several levels of parent-child type relationship - I'm not sure whether this will affect the ability to use a stream reader rather than loading the data into memory as a block. One way I can see of making it work is to perform the simple analysis using a stream-based approach and perhaps wrapping the XPath statements into XSLT transformations that I could run across the files afterward, although it seems a little convoluted. Alternately I know that there are some elements that the XPath queries will not run across, so I guess I could break the document up into a series of smaller fragments based on it's original tree structure, which could perhaps be small enough to process in memory without causing too much havoc. I've tried to explain my objective here so if I'm barking up totally the wrong tree in terms of general approach I'm sure you folks can set me right...

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• Dynamic Linq Property Converting to Sql

  - by Matthew Hood

  I am trying to understand dynamic linq and expression trees. Very basically trying to do an equals supplying the column and value as strings. Here is what I have so far private IQueryable<tblTest> filterTest(string column, string value) { TestDataContext db = new TestDataContext(); // The IQueryable data to query. IQueryable<tblTest> queryableData = db.tblTests.AsQueryable(); // Compose the expression tree that represents the parameter to the predicate. ParameterExpression pe = Expression.Parameter(typeof(tblTest), "item"); Expression left = Expression.Property(pe, column); Expression right = Expression.Constant(value); Expression e1 = Expression.Equal(left, right); MethodCallExpression whereCallExpression = Expression.Call( typeof(Queryable), "Where", new Type[] { queryableData.ElementType }, queryableData.Expression, Expression.Lambda<Func<tblTest, bool>>(e1, new ParameterExpression[] { pe })); // Create an executable query from the expression tree. IQueryable<tblTest> results = queryableData.Provider.CreateQuery<tblTest>(whereCallExpression); return results; } That works fine for columns in the DB. But fails for properties in my code eg public partial class tblTest { public string name_test { get { return name; } } } Giving an error cannot be that it cannot be converted into SQL. I have tried rewriting the property as a Expression<Func but with no luck, how can I convert simple properties so they can be used with linq in this dynamic way? Many Thanks

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