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  • Convert C# Lambda to vb.net

    - by Joven
    Need Help in converting this to VB.NET public void GetCustomers(Action<IEnumerable<Customer>> onSuccess, Action<Exception> onFail) { Manager.Customers.ExecuteAsync(op => { if (op.CompletedSuccessfully) { if (onSuccess != null) onSuccess(op.Results); } else { if (onFail != null) { op.MarkErrorAsHandled(); onFail(op.Error); } } } ); }

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  • Nested for_each with lambda not possible?

    - by Ela782
    The following code does not compile in VS2012, it gives error C2064: term does not evaluate to a function taking 1 arguments on the line of the second for_each (line 4 below). vector<string> v1; for_each(begin(v1), end(v1), [](string s1) { vector<string> v2; for_each(begin(v2), end(v2), [](string s2) { cout << "..."; }); }); I found some related stuff like http://connect.microsoft.com/VisualStudio/feedback/details/560907/capturing-variables-in-nested-lambdas which shows a bug (they are doing something different) but on the other hand that shows that what I print above should be possible. What's wrong with the above code?

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  • Extract information from a Func<bool, T> or alike lambda

    - by Syska
    I''m trying to build a generic cache layer. ICacheRepository Say I have the following: public class Person { public int PersonId { get; set; } public string Firstname { get; set; } public string Lastname { get; set; } public DateTime Added { get; set; } } And I have something like this: list.Where(x => x.Firstname == "Syska"); Here I want to extract the above information, to see if the query supplied the "PersonId" which it did not, so I dont want to cache it. But lets say I run a query like this: list.Where(x => x.PersonId == 10); Since PersonId is my key ... I want to cache it. with the key like "Person_10" and I later can fetch it from the cache. I know its possible to extract the information with Expression<Func<>> but there seems to be a big overhead of doing this (when running compile and extract the Constant values etc. and a bunch of cache to be sure to parse right) Are there a framework for this? Or some smart/golden way of doing this ?

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  • Lambda expression will not compile

    - by John Soer
    I am very confused. I have this lamba expression: tvPatientPrecriptionsEntities.Sort((p1, p2) => p1.MedicationStartDate .Value .CompareTo(p2.MedicationStartDate.Value)); Visual Studio will not compile it and complains about syntax. I converted the lamba expression to an anonymous delegate as so: tvPatientPrecriptionsEntities.Sort( delegate(PatientPrecriptionsEntity p1, PatientPrecriptionsEntity p2) { return p1.MedicationStartDate .Value .CompareTo(p2.MedicationStartDate.Value); }); and it works fine. The project uses .NET 3.5 and I have a reference to System.Linq.

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  • How to pass data to a C++0x lambda function that will run in a different thread?

    - by Dimitri C.
    In our company we've written a library function to call a function asynchronously in a separate thread. It works using a combination of inheritance and template magic. The client code looks as follows: DemoThread thread; std::string stringToPassByValue = "The string to pass by value"; AsyncCall(thread, &DemoThread::SomeFunction, stringToPassByValue); Since the introduction of lambda functions I'd like to use it in combination with lambda functions. I'd like to write the following client code: DemoThread thread; std::string stringToPassByValue = "The string to pass by value"; AsyncCall(thread, [=]() { const std::string someCopy = stringToPassByValue; }); Now, with the Visual C++ 2010 this code doesn't work. What happens is that the stringToPassByValue is not copied. Instead the "capture by value" feature passes the data by reference. The result is that if the function is executed after stringToPassByValue has gone out of scope, the application crashes as its destructor is called already. So I wonder: is it possible to pass data to a lambda function as a copy? Note: One possible solution would be to modify our framework to pass the data in the lambda parameter declaration list, as follows: DemoThread thread; std::string stringToPassByValue = "The string to pass by value"; AsyncCall(thread, [=](const std::string stringPassedByValue) { const std::string someCopy = stringPassedByValue; } , stringToPassByValue); However, this solution is so verbose that our original function pointer solution is both shorter and easier to read. Update: The full implementation of AsyncCall is too big to post here. In short, what happens is that the AsyncCall template function instantiates a template class holding the lambda function. This class is derived from a base class that contains a virtual Execute() function, and upon an AsyncCall() call, the function call class is put on a call queue. A different thread then executes the queued calls by calling the virtual Execute() function, which is polymorphically dispatched to the template class which then executes the lambda function.

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  • Executing a modified expression

    - by Sam
    I found this brief demo: http://msdn.microsoft.com/en-us/library/bb546136.aspx Which discusses modifying an expression. However the code starts with a Expression<Func<string, bool>> and ends up with a Expression so it's not complete. How do I take that expression and make it typed as Expression<Func<string,bool>> again? All the examples I have have found on executing an expression all involve dynamically created expressions which is not what this case has. Here the original expression is defined at compile time. And the code I want to write to do this won't know much about the expression, ideally as little as possible. I definately can't see how I would know what "Paramaters" to pass to Expression.LambdaExpression... In my particular case I want to search for any references to a particular propery of type A and swap them out with a reference to a property of type B then pass the expression to a call to IEnumerable.Where. ie. p=>p.Name == "Sam" where P is Foo1 becomes p=>p.FirstName == "Sam" where p is Foo2

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  • C# LINQ Where Predicate Type Arguments

    - by blu
    I have an XElement with values for mock data. I have an expression to query the xml: Expression<Func<XElement, bool>> simpleXmlFunction = b => int.Parse(b.Element("FooId").Value) == 12; used in: var simpleXml = xml.Elements("Foo").Where(simpleXmlFunction).First(); The design time error is: The type arguments for method 'System.Linq.Enumerable.Where(System.Collections.Generic.IEnumerable, System.Func)' cannot be inferred from the usage. Try specifying the type arguments explicitly' The delegate supplied to Where should take in an XElement and return a bool, marking if the item matches the query, I am not sure how to add anything more to the delegate or the where clause to mark the type. Also, the parallel method for the real function against the Entity Framework does not have this issue. What is not correct with the LINQ-to-XML version?

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  • LinqToXML why does my object go out of scope? Also should I be doing a group by?

    - by Kettenbach
    Hello All, I have an IEnumerable<someClass>. I need to transform it into XML. There is a property called 'ZoneId'. I need to write some XML based on this property, then I need some decendent elements that provide data relevant to the ZoneId. I know I need some type of grouping. Here's what I have attempted thus far without much success. **inventory is an IEnumerable<someClass>. So I query inventory for unique zones. This works ok. var zones = inventory.Select(c => new { ZoneID = c.ZoneId , ZoneName = c.ZoneName , Direction = c.Direction }).Distinct(); No I want to create xml based on zones and place. ***place is a property of 'someClass'. var xml = new XElement("MSG_StationInventoryList" , new XElement("StationInventory" , zones.Select(station => new XElement("station-id", station.ZoneID) , new XElement("station-name", station.ZoneName)))); This does not compile as "station" is out of scope when I try to add the "station-name" element. However is I remove the paren after 'ZoneId', station is in scope and I retreive the station-name. Only problem is the element is then a decendant of 'station-id'. This is not the desired output. They should be siblings. What am I doing wrong? Lastly after the "station-name" element, I will need another complex type which is a collection. Call it "places'. It will have child elements called "place". its data will come from the IEnumerable and I will only want "places" that have the "ZoneId" for the current zone. Can anyone point me in the right direction? Is it a mistake select distinct zones from the original IEnumerable? This object has all the data I need within it. I just need to make it heirarchical. Thanks for any pointers all. Cheers, Chris in San Diego

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  • How can i filter a list of objects using lamda expression?

    - by Colour Blend
    I know i shouldn't have id's with the same value. This is just fictitious, so overlook that. I have: List<Car> carList = new List<Car>(); carList.Add(new Car() { id = 1, name = "Honda" }); carList.Add(new Car() { id = 2, name = "Toyota" }); carList.Add(new Car() { id = 1, name = "Nissan" }); I want to use Lamda Expression to retreive all cars that have an id of 1. Anticipated Result: -- Id: 1, Name: Honda -- Id: 1, Name: Nissan The problem is more filtering an object list based on a foriegn key. Please help me.

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  • Regular Expressions Quick Reference

    - by Jan Goyvaerts
    The Regular-Expressions.info website has a new quick reference to regular expressions that lists all of the regex syntax in one single table along with a link to the tutorial section that explains the syntax. The quick reference is ordered by syntax whereas the full reference tables are ordered by feature. There are multiple entries for some of the syntax as different regex flavors may use the same syntax for different features. Use the quick reference if you’ve seen some syntax in somebody else’s regex and you have no idea what feature that syntax is for. Use the full reference tables if you already know the feature you want but forgot which syntax to use. Of course, an even quicker reference is to paste your regex into RegexBuddy, select the application you’re working with, and click on the part of the regex you don’t understand. RegexBuddy then selects the corresponding node in its regex tree which summarizes exactly what the syntax you clicked on does in your regex. If you need more information, press F1 or click the Explain Token button to open the relevant page in the regex tutorial in RegexBuddy’s help file.

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  • Regular Expressions Cookbook Ebook Deal of the Day

    - by Jan Goyvaerts
    Every day O’Reilly has an “ebook deal of the day” offering one or a bunch of their books in electronic format for only $9.99. Twice this year I received an email from O’Reilly notifying me that Regular Expressions Cookbook was on sale. But each time the email was sent on the morning of the day itself. When it’s morning in California it’s already bedtime for me here in Thailand. So I never saw the emails until the next day, making it rather pointless to blog about the deal. But this time O’Reilly has listened to my request for advance notification. I just got an email this morning saying Regular Expressions Cookbook will be part of the Ebook Deal of the Day for 15 September 2010. That’s 15 September on the US west coast. When I write this there’s a few hours to go before the deal starts at one past midnight California time. You can get any O’Reilly Cookbook as an ebook for only $9.99. The normal price for Regular Expressons Cookbook as an ebook is $31.99. The download includes the book in PDF, ePub, Mobi (for Kindle), DAISY, and Android formats.

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  • Lighttpd Regular Expressions

    - by Kyle
    I am trying to match any url that has /images/ , /styles/ , or /scripts/ in a lighttpd $HTTP["url"] statement. How could this be done? I am currently using "^/images/" , etc. and it's only working if that directory is in the beginning of the URL.

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  • Regular Expressions: Positive Lookahead and Word Border question

    - by Inf.S
    Hello again Stackoverflow people! Assume I have these words: smartphones, smartphone I want to match the substring "phone" from within them. However, in both case, I want only "phone" to be returned, not "phones" in the first case. In addition to this, I want matches only if the word "phone" is a suffix only, such that: fonephonetics (just an example) is not matched. I assumed that the regex (phone([?=s])?)\b would give me what I need, but it is currently matching "phones" and "phone", but not the "fonephonetics" one. I don't need "phones". I want "phone" for both cases. Any ideas about what is wrong, and what I can do? Thank you in advance!

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  • Sort a List<T> using query expressions - LINQ C#

    - by Dan Yack
    I have a problem using Linq to order a structure like this : public class Person { public int ID { get; set; } public List<PersonAttribute> Attributes { get; set; } } public class PersonAttribute { public int ID { get; set; } public string Name { get; set; } public string Value { get; set; } } A person might go like this: PersonAttribute Age = new PersonAttribute { ID = 8, Name = "Age", Value = "32" }; PersonAttribute FirstName = new PersonAttribute { ID = 9, Name = "FirstName", Value = "Rebecca" }; PersonAttribute LastName = new PersonAttribute { ID = 10, Name = "LastName", Value = "Johnson" }; PersonAttribute Gender = new PersonAttribute { ID = 11, Name = "Gender", Value = "Female" }; I would like to use LINQ projection to sort a list of persons ascending by the person attribute of my choice, for example, sort on Age, or sort on FirstName. I am trying something like string mySortAttribute = "Age" PersonList.OrderBy(p => p.PersonAttribute.Find(s => s.Name == mySortAttribute).Value); But the syntax is failing me. Any clues? Thanks in advance!

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  • Evaluating mathematical expressions in Python

    - by vander
    Hi, I want to tokenize a given mathematical expression into a binary tree like this: ((3 + 4 - 1) * 5 + 6 * -7) / 2 '/' / \ + 2 / \ * * / \ / \ - 5 6 -7 / \ + 1 / \ 3 4 Is there any pure Python way to do this? Like passing as a string to Python and then get back as a tree like mentioned above. Thanks.

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  • Conversion of Linq expressions

    - by Arnis L.
    I'm not sure how exactly argument what I'm trying to achieve, therefore - wrote some code: public class Foo{ public Bar Bar{get;set;} } public class Bar{ public string Fizz{get;set;} } public class Facts{ [Fact] public void fact(){ Assert.Equal(expectedExp(),barToFoo(barExp())); } private Expression<Func<Foo,bool>> expectedExp(){ return f=>f.Bar.Fizz=="fizz"; } private Expression<Func<Bar,bool>> barExp(){ return b=>b.Fizz=="fizz"; } private Expression<Func<Foo,bool>> barToFoo (Expression<Func<Bar,bool>> barExp){ return Voodoo(barExp); //<-------------------------------------------??? } } Is this even possible?

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  • Understanding Regular Expressions (focus on URL Rewrite)–Part 11 (Sub-Part 2 of 2)

    - by OWScott
    This 2nd part (out of 2) on Regular Expressions covers the remaining tips necessary to get up to speed on a topic that at first seems daunting, but really isn’t that bad. Whether you use Regular Expressions for URL Rewrite, Visual Studio, PowerShell, programming or any other tool, these tips will allow you to understand the essentials of Regular Expressions. Be sure to watch Part 1 first. This is week 11 of a 52 week series on various web administration related tasks. Past and future videos can be found here.

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  • Visual Studio 2010 Find and Replace With Regular Expressions

    - by Lance Robinson
    Here is a quick notes about using regular expressions in the VS2010 Find Replace dialog.  1.  To create a backreference, use curly braces (“{“ and “}” ) instead of regular parentheses. 2.  To use the captured backreference, use \1\2 etc, where \1 is the first captured value, \2 is the second captured value, etc. Example: I want to find*: info.setFieldValue(param1, param2); and replace it with: SetFieldValue(info, param1, param2); To do this, I can use the following find/replace values: Find what: {[a-zA-Z0-9]+}.setFieldValue\({[a-zA-Z0-9., ]+}\); Replace with: SetFieldValue(\1, \2); Use Regular Expressions is checked, of course. *If you’re wondering why I’d want to do this – because I don’t have control over the setFieldValue function – its in a third party library that doesn’t behave in a very friendly manner. Technorati Tags: Visual Studio,Regular Expressions

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  • Regular Expressions Reference Tables Updated

    - by Jan Goyvaerts
    The regular expressions reference on the Regular-Expressions.info website was completely overhauled with the big update of that site last month. In the past, the reference section consisted of two parts. One part was a summary of the regex features commonly found in Perl-style regex flavors with short descriptions and examples. This part of the reference ignored differences between regex flavors and omitted most features that don’t have wide support. The other part was a regular expression flavor comparison that listed many more regex features along with YES/no indicators for many regex flavors, but without any explanations of the features. When reworking the site, I wanted to make the reference section more detailed, with descriptions and examples of all the syntax supported by the flavors discussed on the site. Doing that resulted in a reference that lists many features that are only supported by a few regex flavors. For such a reference to be usable, it needs to indicate which flavors support each feature. My original design for the new reference table used two rows for each feature. The first row had 4 columns with a label, syntax, description, and example, similar to the old reference tables. The second row had 20 columns indicating which versions of which flavors support these features. While the double-row design allowed all the information to fit within the table without requiring horizontal scrolling, it made it more difficult to quickly scan the tables for the feature you’re looking for. To make the new reference tables easier to read, they now have only a single row for each feature. The first 4 columns are the same as before. The remaining two columns show which versions of two regular expression flavors support the feature. You can use the drop-down lists above the table to choose the flavors the table should indicate. The site uses cookies to allow the flavor choices to persist while you navigate the reference. The result of this latest update is that the new regex tables are now just as easy to read as the ten-year-old tables on the old site were, while still covering all the features big and small of all the flavors discussed on the site.

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  • Second Edition of Regular Expressions Cookbook Has Been Published

    - by Jan Goyvaerts
    %COOKBOOKFRAME% The first edition of Regular Expressions Cookbook was published in May of 2009. It quickly became a bestseller, briefly holding the #1 spot in computer books on Amazon.com. It also had staying power. The ebook version was O’Reilly’s top seller during the whole year of 2010. So it’s no surprise that our editor at O’Reilly soon contacted us for a second edition. With Steven and I always being very busy, those plans were delayed until finally both of us found the time to update the book. Work started in January. Today you can buy your own copy of the second edition of Regular Expressions Cookbook. O’Reilly’s online shop sells the eBook in DRM-free ePub, Mobi, and PDF formats for $39.99 and the print version for $49.99. These are the list prices for the eBook and the print book. If you’re looking for a discount and free shipping of the print book, you can pre-order on one of the various Amazon sites. Deliveries should start soon. The discount rates differ and are subject to change. Amazon will also pay me an affiliate commission if you use one of these links, which pretty much doubles the income I get from the book. Amazon.com. Free shipping to the USA. Amazon.co.uk. Free shipping to the UK and Ireland. Amazon.fr. Free shipping to France, Monaco, Luxembourg, and Belgium. Amazon.de. Free shipping to Germany, Austria, Switzerland, Luxembourg, Liechtenstein, Belgium, and The Netherlands. If you don’t want to wait for the print book to arrive, the Kindle edition is already available for instant delivery. The Kindle edition works on Amazon’s Kindle hardware, and on PCs via Amazon’s Kindle software (free download). Amazon.com Amazon.co.uk Amazon.fr Amazon.de I’ll blog more about the book in the coming days and weeks with details about what’s new in the second edition.

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