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  • XML Schema: Namespace issues when importing shared elements

    - by netzwerg
    When trying to import shared definitions from a XML Schema, I can properly reference shared types, but referencing shared elements causes validation errors. This is the schema that imports the shared definitions (example.xsd): <?xml version="1.0" encoding="UTF-8"?> <xs:schema elementFormDefault="qualified" xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns:shared="http://shared.com"> <xs:import namespace="http://shared.com" schemaLocation="shared.xsd"/> <xs:element name="example"> <xs:complexType> <xs:sequence> <xs:element ref="importedElement"/> <xs:element ref="importedType"/> </xs:sequence> </xs:complexType> </xs:element> <xs:element name="importedElement"> <xs:complexType> <xs:sequence> <xs:element ref="shared:fooElement"/> </xs:sequence> </xs:complexType> </xs:element> <xs:element name="importedType"> <xs:complexType> <xs:sequence> <xs:element name="bar" type="shared:barType"/> </xs:sequence> </xs:complexType> </xs:element> </xs:schema> These are the shared definitions (shared.xsd): <?xml version="1.0" encoding="UTF-8"?> <xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns="http://shared.com" targetNamespace="http://shared.com"> <xs:element name="fooElement"> <xs:simpleType> <xs:restriction base="xs:integer"/> </xs:simpleType> </xs:element> <xs:simpleType name="barType"> <xs:restriction base="xs:integer"/> </xs:simpleType> </xs:schema> Now consider this XML instance: <?xml version="1.0"?> <example xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="example.xsd"> <importedElement> <fooElement>42</fooElement> </importedElement> <importedType> <bar>42</bar> </importedType> </example> When validated, the "importedType" works perfectly fine, but the "importedElement" gives the following error: Invalid content was found starting with element 'fooElement'. One of '{"http://shared.com":fooElement}' is expected I would guess that my troubles are related to namespace issues (hence the somehow misleading "got fooElement but was expecting fooElement") -- any hints on what's wrong here?

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  • How to Zip one IEnumerable with itself

    - by wageoghe
    I am implementing some math algorithms based on lists of points, like Distance, Area, Centroid, etc. Just like in this post: http://stackoverflow.com/questions/2227828/find-the-distance-required-to-navigate-a-list-of-points-using-linq That post describes how to calculate the total distance of a sequence of points (taken in order) by essentially zipping the sequence "with itself", generating the sequence for Zip by offsetting the start position of the original IEnumerable by 1. So, given the Zip extension in .Net 4.0, assuming Point for the point type, and a reasonable Distance formula, you can make calls like this to generate a sequence of distances from one point to the next and then to sum the distances: var distances = points.Zip(points.Skip(1),Distance); double totalDistance = distances.Sum(); Area and Centroid calculations are similar in that they need to iterate over the sequence, processing each pair of points (points[i] and points[i+1]). I thought of making a generic IEnumerable extension suitable for implementing these (and possibly other) algorithms that operate over sequences, taking two items at a time (points[0] and points[1], points[1] and points[2], ..., points[n-1] and points[n] (or is it n-2 and n-1 ...) and applying a function. My generic iterator would have a similar signature to Zip, but it would not receive a second sequence to zip with as it is really just going to zip with itself. My first try looks like this: public static IEnumerable<TResult> ZipMyself<TSequence, TResult>(this IEnumerable<TSequence> seq, Func<TSequence, TSequence, TResult> resultSelector) { return seq.Zip(seq.Skip(1),resultSelector); } With my generic iterator in place, I can write functions like this: public static double Length(this IEnumerable<Point> points) { return points.ZipMyself(Distance).Sum(); } and call it like this: double d = points.Length(); and double GreensTheorem(Point p1, Point p1) { return p1.X * p2.Y - p1.Y * p2.X; } public static double SignedArea(this IEnumerable<Point> points) { return points.ZipMyself(GreensTheorem).Sum() / 2.0 } public static double Area(this IEnumerable<Point> points) { return Math.Abs(points.SignedArea()); } public static bool IsClockwise(this IEnumerable<Point> points) { return SignedArea(points) < 0; } and call them like this: double a = points.Area(); bool isClockwise = points.IsClockwise(); In this case, is there any reason NOT to implement "ZipMyself" in terms of Zip and Skip(1)? Is there already something in LINQ that automates this (zipping a list with itself) - not that it needs to be made that much easier ;-) Also, is there better name for the extension that might reflect that it is a well-known pattern (if, indeed it is a well-known pattern)? Had a link here for a StackOverflow question about area calculation. It is question 2432428. Also had a link to Wikipedia article on Centroid. Just go to Wikipedia and search for Centroid if interested. Just starting out, so don't have enough rep to post more than one link,

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  • Using SQLXML Bulk Load in .NET Environment - Error with One to Many relationship on Complex Type

    - by user331111
    Hi, I have an error when I am importing an XML file using SQLXMLBulkLoad, wondering if anyone could help. Error: Data mapping to column 'Attribute' was already found in the data. Make sure that no two schema definitions map to the same column Full files and details can be found here http://www.experts-exchange.com/Microsoft/Development/MS-SQL-Server/SQL-Server-2005/Q_26102239.html Exert from XSD: <sql:relationship name="EnvironmentDECAttributes" parent="Environment" parent-key="intEnvironmentID" child="DECAttributes" child-key="intEnvironmentID"/> <complexType name="Environment"> <sequence> <element name="ESANumber" minOccurs="0"> <annotation> <documentation> Environmentally Sensitive Area Number </documentation> </annotation> <simpleType> <restriction base="string"> <maxLength value="15"/> <whiteSpace value="collapse"/> </restriction> </simpleType> </element> <element name="Conditions" minOccurs="0" sql:relation="Conditions" sql:relationship="EnvironmentConditions"> <complexType> <sequence> <element name="Condition" type="vms:EnvironmentalConditions" minOccurs="0" maxOccurs="5"/> </sequence> </complexType> </element> <element name="DECDistrict" minOccurs="0"> <annotation> <documentation> Department of Environment &amp; Conservation District </documentation> </annotation> <simpleType> <restriction base="string"> <maxLength value="31"/> <whiteSpace value="collapse"/> </restriction> </simpleType> </element> <element name="DECAttributes" minOccurs="0" maxOccurs="1" sql:relation="DECAttributes" sql:relationship="EnvironmentDECAttributes"> <complexType> <sequence> <element name="Attribute" type="vms:DECAttributes" minOccurs="0" maxOccurs="unbounded" sql:field="Attribute"> <annotation> <documentation> Department of Environment &amp; Conservation attributes. </documentation> </annotation> </element> </sequence> </complexType> </element> </sequence> </complexType> Exert from XML: <Environment> <DECAttributes> <Attribute>WA</Attribute> <Attribute>SA</Attribute> </DECAttributes> </Environment> Any help/ comments would be appreciated Thanks C

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  • XSD Schema for XML with multiple structures

    - by Xetius
    I am attempting to write an XML Schema to cover a number of XML conditions which I may encounter. I have the same root element (serviceRequest) with different child elements. I was trying to use the xs:extension element to define multiple versions, but it is complaining about unexpected element orderInclusionCriteria etc. Am I going about this the right way, or is there a better way to define this? The other way I thought about this was to have a single xs:choice with all the options inside it, but this seemed somewhat inelegant. These XSD files are for use within XMLBeans if that makes any difference. I have Given the following 2 examples of XML: 1) <?xml version="1.0" encoding="utf-8"?> <serviceRequest method="GOO" debug="NO"> <sessionId sID="ABC1234567" /> <orderInclusionCriteria accountId="1234567" accountNum="1234567890" /> </serviceRequest> 2) <?xml version="1.0" encoding="utf-8"?> <serviceRequest method="GOO" debug="NO"> <sessionId sID="ABC1234567" /> <action aType='MakePayment'> <makePayment accountID='CH91015165S' amount='5.00' /> </action> </serviceRequest> I thought I could use the following schema file: <?xml version="1.0" encoding="UTF-8"?> <xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"> <xs:element name="serviceRequest" type="ServiceRequestType" /> <xs:element name="session" type="SessionType" /> <xs:attribute name="method" type="xs:string" /> <xs:attribute name="debug" type="xs:string" /> <xs:complexType name="SessionType"> <xs:attribute name="sID" use="required"> <xs:simpleType> <xs:restriction base="xs:string"/> </xs:simpleType> </xs:attribute> </xs:complexType> <xs:complexType name="ServiceRequestType"> <xs:sequence> <xs:element ref="session" /> </xs:sequence> <xs:attribute ref="method" /> <xs:attribute ref="debug" /> </xs:complexType> <xs:complexType name="OrderTrackingServiceRequest"> <xs:complexContent> <xs:extension base="ServiceRequestType"> <xs:complexType> <xs:sequence> <xs:element name="OrderInclusionCriteria" type="xs:string" /> </xs:sequence> </xs:complexType> </xs:extension> </xs:complexContent> </xs:complexType> <xs:complexType name="Action"> <xs:complexContent> <xs:extension base="ServiceRequestType"> <xs:complexType> <xs:sequence> <xs:element name="makePayment"> <xs:complexType> <xs:attribute name="accountID" type="xs:string" /> <xs:attribute name="amount" type="xs:string" /> <xs:complexType> </xs:element> </xs:sequence> <xs:attribute name="aType" type="xs:string" /> </xs:complexType> </xs:extension> </xs:complexContent> </xs:complexType> </xs:schema>

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  • xml validation problem

    - by Hoax
    I'm having trouble validating a schema I created. "cvc-elt.1: Cannot find the declaration of element 'category'." xsd <?xml version="1.0" encoding="UTF-8"?> <xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"> <xs:element name="list"> <xs:complexType> <xs:sequence> <xs:element name="category" type="categoryType" minOccurs="0" maxOccurs="unbounded"/> </xs:sequence> </xs:complexType> </xs:element> <xs:complexType name="categoryType"> <xs:sequence> <xs:element name="name" type="xs:string"/> <xs:element name="desc" type="xs:string"/> <xs:element name="icon" type="xs:base64Binary"/> <xs:element name="poi" type="poiType" minOccurs="0" maxOccurs="unbounded"/> </xs:sequence> </xs:complexType> <xs:complexType name="poiType"> <xs:sequence> <xs:element name="name" type="xs:string"/> <xs:element name="desc" type="xs:string"/> <xs:element name="longitude" type="xs:long"/> <xs:element name="latitude" type="xs:long"/> <xs:element name="url" type="xs:string" minOccurs="0" maxOccurs="unbounded"/> <xs:element name="image" type="xs:base64Binary" minOccurs="0" maxOccurs="unbounded"/> </xs:sequence> </xs:complexType> </xs:schema> xml <?xml version="1.0" encoding="UTF-8"?> <list SchemaLocation="sem.xsd"> <category> <name>Sehenswürdigkeiten</name> <desc>sehenswerte und berühmte Orte, die man gesehen haben muss</desc> <icon>...</icon> <poi> <name>Linzer Landhaus</name> <desc>Sitz des Oberösterreichsichen Landtags</desc> <url>http://www.linz.at/tourismus/7569.asp</url> <longitude>48.304107</longitude> <latitude>14.286025</latitude> <image>...</image> </poi> <poi> <name>Ars Electronica</name> <desc>Museum der digitalen Künste</desc> <url>http://www.aec.at</url> <longitude>48.309788</longitude> <latitude>14.284179</latitude> <image>...</image> <image>...</image> </poi> </category> <category>...</category> </list> any idea whats wrong? cheers hoax

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  • simple XML question for perl - how to retrieve specific elements

    - by Jeff
    I'm trying to figure out how to loop through XML but I've read a lot and I'm still getting stuck. Here's the info: I'm using the wordnik api to retrieve XML with XML::Simple: $content = get($url); $r = $xml->XMLin("$content"); The actual XML looks like this: <definitions> - <definition sequence="0" id="0"> - <text> To withdraw one's support or help from, especially in spite of duty, allegiance, or responsibility; desert: abandon a friend in trouble. </text> <headword>abandon</headword> <partOfSpeech>verb-transitive</partOfSpeech> </definition> - <definition sequence="1" id="0"> - <text> To give up by leaving or ceasing to operate or inhabit, especially as a result of danger or other impending threat: abandoned the ship. </text> <headword>abandon</headword> <partOfSpeech>verb-transitive</partOfSpeech> </definition> - <definition sequence="2" id="0"> - <text> To surrender one's claim to, right to, or interest in; give up entirely. See Synonyms at relinquish. </text> <headword>abandon</headword> <partOfSpeech>verb-transitive</partOfSpeech> </definition> - <definition sequence="3" id="0"> ... What I want is simply the FIRST definition's part of speech. I'm using this code but it's getting the LAST definition's POS: if($r->{definition}->{0}->{partOfSpeech}) { $pos = $r->{definition}->{0}->{partOfSpeech}; } else { $pos = $r->{definition}->{partOfSpeech}; } I am pretty embarrassed by this since I know there's an obviously better way to do it. I would love to get something as simple as this working so I could more generally loop through the elements. BUt it just isn't working for me (no idea what to reference). I've tried many variations of the following - this is just my last attempt: while (my ($k, $v) = each %{$r->{definitions}->{definition}[0]->{sequence}->{partOfSpeech}}) { $v =~ s/'/'"'"'/g; $v = "'$v'"; print "export $k=$v\n"; } Lastly, when I do "print Dumper($r)" it gives me this: $VAR1 = { 'definition' => { '0' => { 'partOfSpeech' => 'noun', 'sequence' => '6', 'text' => 'A complete surrender of inhibitions.', 'headword' => 'abandon' } } }; (And that "noun" you see is the last (6th) definition/partofspeech element).

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  • XML and XSD - use element name as replacement of xsi:type for polymorphism

    - by disown
    Taking the W3C vehicle XSD as an example: <schema xmlns="http://www.w3.org/2001/XMLSchema" targetNamespace="http://cars.example.com/schema" xmlns:target="http://cars.example.com/schema"> <complexType name="Vehicle" abstract="true"/> <complexType name="Car"> <complexContent> <extension base="target:Vehicle"/> ... </complexContent> </complexType> <complexType name="Plane"> <complexContent> <extension base="target:Vehicle"/> <sequence> <element name="wingspan" type="integer"/> </sequence> </complexContent> </complexType> </schema> , and the following definition of 'meansOfTravel': <complexType name="MeansOfTravel"> <complexContent> <sequence> <element name="transport" type="target:Vehicle"/> </sequence> </complexContent> </complexType> <element name="meansOfTravel" type="target:MeansOfTravel"/> With this definition you need to specify the type of your instance using xsi:type, like this: <meansOfTravel> <transport xsi:type="Plane"> <wingspan>3</wingspan> </transport> </meansOfTravel> I would just like to acheive a 'name of type' - 'name of element' mapping so that this could be replaced with just <meansOfTravel> <plane> <wingspan>3</wingspan> </plane> </meansOfTravel> The only way I could do this until now is by making it explicit: <complexType name="MeansOfTravel"> <sequence> <choice> <element name="plane" type="target:Plane"/> <element name="car" type="target:Car"/> </choice> </sequence> </complexType> <element name="meansOfTravel" type="target:MeansOfTravel"/> But this means that I have to list all possible sub-types in the 'MeansOfTravel' complex type. Is there no way of making the XML parser assume that you mean a 'Plane' if you call the element 'plane'? Or do I have to make the choice explicit? I would just like to keep my design DRY - if you have any other suggestions (like groups or so) - i would love to hear them.

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  • Can I create an xml that specifies element from 2 nested xsd's without using a prefixes?

    - by TweeZz
    I have 2 xsd's which are nested: DefaultSchema.xsd: <?xml version="1.0" encoding="utf-8"?> <xs:schema id="DefaultSchema" targetNamespace="http://myNamespace.com/DefaultSchema.xsd" elementFormDefault="qualified" xmlns="http://myNamespace.com/DefaultSchema.xsd" xmlns:xs="http://www.w3.org/2001/XMLSchema" > <xs:complexType name="ZForm"> <xs:sequence minOccurs="0" maxOccurs="unbounded"> <xs:element name="Part" minOccurs="0" maxOccurs="unbounded" type="Part"/> </xs:sequence> <xs:attribute name="Title" use="required" type="xs:string"/> <xs:attribute name="Version" type="xs:int"/> </xs:complexType> <xs:complexType name="Part"> <xs:sequence minOccurs="0" maxOccurs="unbounded"> <xs:element name="Label" type="Label" minOccurs="0"></xs:element> </xs:sequence> <xs:attribute name="Title" use="required" type="xs:string"/> </xs:complexType> <xs:complexType name="Label"> <xs:simpleContent> <xs:extension base="xs:string"> <xs:attribute name="Title" type="xs:string"/> </xs:extension> </xs:simpleContent> </xs:complexType> </xs:schema> ExportSchema.xsd: (this one kinda wraps 1 more element (ZForms) around the main element (ZForm) of the DefaultSchema) <?xml version="1.0" encoding="utf-8"?> <xs:schema id="ExportSchema" targetNamespace="http://myNamespace.com/ExportSchema.xsd" elementFormDefault="qualified" xmlns="http://myNamespace.com/DefaultSchema.xsd" xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns:es="http://myNamespace.com/ExportSchema.xsd" > <xs:import namespace="http://myNamespace.com/DefaultSchema.xsd" schemaLocation="DefaultSchema.xsd"/> <xs:element name="ZForms" type="es:ZFormType"></xs:element> <xs:complexType name="ZFormType"> <xs:sequence> <xs:element name="ZForm" type="ZForm" maxOccurs="unbounded" /> </xs:sequence> </xs:complexType> </xs:schema> And then finally I have a generated xml: <?xml version="1.0" encoding="utf-8"?> <ZForms xmlns="http://myNamespace.com/ExportSchema.xsd"> <ZForm Version="1" Title="FormTitle"> <Part Title="PartTitle" > <Label Title="LabelTitle" /> </Part> </ZForm> </ZForms> Visual studio complains it doesn't know what 'Part' is. I was hoping I do not need to use xml namespace prefixes (..) to make this xml validate, since ExportSchema.xsd has a reference to the DefaultSChema.xsd. Is there any way to make that xml structure valid without explicitly specifying the DefaultSchema.xsd? Or is this a no go?

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  • LINQ – TakeWhile and SkipWhile methods

    - by nmarun
    I happened to read about these methods on Vikram's blog and tried testing it. Somehow when I saw the output, things did not seem to add up right. I’m writing this blog to show the actual workings of these methods. Let’s take the same example as showing in Vikram’s blog and I’ll build around it. 1: int[] numbers = { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 }; 2:  3: foreach(var number in numbers.TakeWhile(n => n < 7)) 4: { 5: Console.WriteLine(number); 6: } Now, the way I (incorrectly) read the upper bound condition in the foreach loop was: ‘Give me all numbers that pass the condition of n<7’. So I was expecting the answer to be: 5, 4, 1, 3, 2, 0. But when I run the application, I see only: 5, 4, 1,3. Turns out I was wrong (happens at least once a day). The documentation on the method says ‘Returns elements from a sequence as long as a specified condition is true. To show in code, my interpretation was the below code’: 1: foreach (var number in numbers) 2: { 3: if (number < 7) 4: { 5: Console.WriteLine(number); 6: } 7: } But the actual implementation is: 1: foreach(var number in numbers) 2: { 3: if(number < 7) 4: { 5: Console.WriteLine(number); 6: break; 7: } 8: } So there it is, another situation where one simple word makes a difference of a whole world. The SkipWhile method has been implemented in a similar way – ‘Bypasses elements in a sequence as long as a specified condition is true and then returns the remaining elements’ and not ‘Bypasses elements in a sequence where a specified condition is true and then returns the remaining elements’. (Subtle.. very very subtle). It’s feels strange saying this, but hope very few require to read this article to understand these methods.

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  • SQL SERVER – Online Session on What is New in Denali – Today Online

    - by pinaldave
    I will be presenting today on subject Inside of Next Generation SQL Server – Denali online at Zeollar.com. This sessions are really fun as they are online, downloadable, and 100% demo oriented. I will be using SQL Server ‘Denali’ CTP 1 to present on the subject of What is New in Denali. The webcast will start at 12:30 PM sharp and will end at 1 PM India Time. It will be 100% demo oriented and no slides. I will be covering following topics in the session. SQL SERVER – Denali Feature – Zoom Query Editor SQL SERVER – Denali – Improvement in Startup Options SQL SERVER – Denali – Clipboard Ring – CTRL+SHIFT+V SQL SERVER – Denali – Multi-Monitor SSMS Windows SQL SERVER – Denali – Executing Stored Procedure with Result Sets SQL SERVER – Performance Improvement with of Executing Stored Procedure with Result Sets in Denali SQL SERVER – ‘Denali’ – A Simple Example of Contained Databases SQL SERVER – Denali – ObjectID in Negative – Local TempTable has Negative ObjectID SQL SERVER – Server Side Paging in SQL Server Denali – A Better Alternative SQL SERVER – Server Side Paging in SQL Server Denali Performance Comparison SQL SERVER – Denali – SEQUENCE is not IDENTITY SQL SERVER – Denali – Introduction to SEQUENCE – Simple Example of SEQUENCE If time permits we will cover few more topics as well. The session will be recorded as well. My earlier session on the Topic of Best Practices Analyzer is also available to watch online here: SQL SERVER – Video – Best Practices Analyzer using Microsoft Baseline Configuration Analyzer Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: Pinal Dave, PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, SQLServer, T SQL, Technology

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  • LINQ: Single vs. First

    - by Paulo Morgado
    I’ve witnessed and been involved in several discussions around the correctness or usefulness of the Single method in the LINQ API. The most common argument is that you are querying for the first element on the result set and an exception will be thrown if there’s more than one element. The First method should be used instead, because it doesn’t throw if the result set has more than one item. Although the documentation for Single states that it returns a single, specific element of a sequence of values, it actually returns THE single, specific element of a sequence of ONE value. One you use the Single method in your code you are asserting that your query will result in a scalar result instead of a result set of arbitrary length. On the other hand, the documentation for First states that it returns the first element of a sequence of arbitrary length. Imagine you want to catch a taxi. You go the the taxi line and catch the FIRST one, no matter how many are there. On the other hand, if you go the the parking lot to get your car, you want the SINGLE one specific car that’s yours. If your “query” “returns” more than one car, it’s an exception. Either because it “returned” not only your car or you happen to have more than one car in that parking lot. In either case, you can only drive one car at once and you’ll need to refine your “query”.

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  • Project Euler 14: (Iron)Python

    - by Ben Griswold
    In my attempt to learn (Iron)Python out in the open, here’s my solution for Project Euler Problem 14.  As always, any feedback is welcome. # Euler 14 # http://projecteuler.net/index.php?section=problems&id=14 # The following iterative sequence is defined for the set # of positive integers: # n -> n/2 (n is even) # n -> 3n + 1 (n is odd) # Using the rule above and starting with 13, we generate # the following sequence: # 13 40 20 10 5 16 8 4 2 1 # It can be seen that this sequence (starting at 13 and # finishing at 1) contains 10 terms. Although it has not # been proved yet (Collatz Problem), it is thought that all # starting numbers finish at 1. Which starting number, # under one million, produces the longest chain? # NOTE: Once the chain starts the terms are allowed to go # above one million. import time start = time.time() def collatz_length(n): # 0 and 1 return self as length if n <= 1: return n length = 1 while (n != 1): if (n % 2 == 0): n /= 2 else: n = 3*n + 1 length += 1 return length starting_number, longest_chain = 1, 0 for x in xrange(1, 1000001): l = collatz_length(x) if l > longest_chain: starting_number, longest_chain = x, l print starting_number print longest_chain # Slow 31 seconds print "Elapsed Time:", (time.time() - start) * 1000, "millisecs" a=raw_input('Press return to continue')

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  • libgdx actors and instant actions

    - by vaati
    I'm having trouble with actors and actions. I have a list of actors, they all have either no action, or 1 sequence action This sequence action has either : a couple of actions (some are instant, some have duration 0) a couple of actions followed by a parallel action. My problem is the following: some of the instant actions are used to set the position and the alpha of the actor. So when one of the action is "move to x,y and set alpha to 0" the actor is visible for one frame at position 0,0 , move instantly to x,y for the next frame, and then disappears. Though this behaviours is to be expected, I want to avoid it. How can I achieve that? I tried to intercept the actions before I put actors in the stage but I need the stage width/height for some actions. So something like : Action actionSequence = actor.getActions().get(0); Array<Action> actions = ((SequenceAction) actionSequence).getActions(); for(Action act : actions){ if(act.act(0)) System.out.println("action " + act.toString() + " successfully run"); else System.out.println("action " + act.toString() + " wasn't instant"); } won't work. It gets even more complicated when an actor can also have a repeat action in stead of the sequence action (because you have to only run the actions that have duration 0 once without repeat, and then start the repeat). Any help is appreciated.

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  • Bejeweled-like game, managing different gem/powerup behaviors?

    - by Wissam
    I thought I'd ask a question and look forward to some insight from this very compelling community. In a Bejeweled-like (Match 3) game, the standard behavior once a valid swap of two adjacent tiles is made is that the resulting matching tiles are destroyed, any tiles now sitting over empty spaces fall to the position above the next present-tile, and any void created above is filled with new tiles. In richer Match-3 games like Bejeweled, 4 in a row (as opposed to just 3) modifies this behavior such that the tile that was swapped is retained, turned into a "flaming" gem, it falls, and then the empty space above is filled. The next time that "flaming gem" is played it explodes and destroys the 8 perimeter tiles, triggers a different animation sequence (neighbors of those 8 tiles being destroyed look like they've been hit by a shockwave then they fall to their respective positions). Scoring is different, the triggered sounds are different, etc. There are even more elaborate behaviors for Match5, Match-cross-pattern, and many powerups that can be purchased, each which produces a more elaborate sequence of events, sounds, animations, scoring, etc... What is the best approach to developing all these different behaviors that respond to players' "move" and her current "performance" and that deviate from the standard sequence of events, scoring, animation, sounds etc, in such a way that we can always flexibly introduce a new "powerup" ? What we are doing now is hard-coding the events of each one, but the task is long and arduous and seems like the wrong approach especially since the game-designers and testers often offer (later) valuable insight on what works better in-game, which means that the code itself may have to be re-written even for minor changes in behavior (say, destroy only 7 neighboring tiles, instead of all 8 in an explosion). ANY pointers for good practices here would be highly appreciated.

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  • Is the way I'm implementing my genetic algorithm right?

    - by Mhjr
    In my graduation project, I am asked to use a genetic algorithm (any variation of it can be chosen) to generate valid timetables. What I did was make a simple program that generates unique sequences representing genes, the sequence is described below: (sorry if it's mathematically incorrect) The only variable in the sequence is the room element, so basically the program takes a tree that goes like this: [Course] -(contains)-> [Units] -(contains)-> [Offerings] -(contains)-> [Instructors] -(contains)-> [Rooms] Each course can have n units (duplicates). Each unit can have n offerings (lectures,lab session, excercises,...). Each offering has only 1 instructor. Each instructor (or the whole lecture composed from the four elements of the sequence) has multiple rooms. When a timetable is initialized, one of these sequences that differ in rooms will be taken into the timetable, so the difference in genes (sequences) of each timetable will be just the rooms random choice and the difference between chromosomes (timetables) will be time placements of these genes (sequences). My question is, before I proceed in implementing what I described, is it valid? Is the representation used here for chromosomes a permutation representation?

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  • Project Euler Problem 14

    - by MarkPearl
    The Problem The following iterative sequence is defined for the set of positive integers: n n/2 (n is even) n 3n + 1 (n is odd) Using the rule above and starting with 13, we generate the following sequence: 13 40 20 10 5 16 8 4 2 1 It can be seen that this sequence (starting at 13 and finishing at 1) contains 10 terms. Although it has not been proved yet (Collatz Problem), it is thought that all starting numbers finish at 1. Which starting number, under one million, produces the longest chain? NOTE: Once the chain starts the terms are allowed to go above one million. The Solution   public static long NextResultOdd(long n) { return (3 * n) + 1; } public static long NextResultEven(long n) { return n / 2; } public static long TraverseSequence(long n) { long x = n; long count = 1; while (x > 1) { if (x % 2 == 0) x = NextResultEven(x); else x = NextResultOdd(x); count++; } return count; } static void Main(string[] args) { long largest = 0; long pos = 0; for (long i = 1000000; i > 1; i--) { long temp = TraverseSequence(i); if (temp > largest) { largest = temp; pos = i; } } Console.WriteLine("{0} - {1}", pos, largest); Console.ReadLine(); }

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  • The [2] table entry '[3]' has no associated entry in the Media table. (error 2602)

    - by derekf
    Coworker started getting the above message in the event log and as dialog during install.  Argument [2] was File and argument [3] was a specific file. Error dialog read   Product: (app name) -- The installer has encountered an unexpected error installing this package. This may indicate a problem with this package. The error code is 2602. Package was a vendor-provided MSI that had been installed administratively, and then a patch (.msp) applied to the administrative install point. With some digging we found that the MSI still had the entries in the media table pointing at the CAB files, and that there were several files at the end of the sequence that did not have corresponding entries in the Media table (last sequence 990 in Media table, last entry in File table had sequence 994).  Attributes on files in the File table all had the msidbFileAttributesCompressed (&16384) attribute set, so they were all expecting to be within the CAB files, but since this was an admin install there were no CAB files. Resolved by clearing the Media table (replace with a single entry: Disk ID 1, LastSequence 994) and going through the file table and subtracting 8192 from each entry to mark files as not compressed.  Tested and worked.

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  • XmlSchema.read throws exception when an element is declared nillable

    - by G33kKahuna
    I have a simple schema that I am trying to read using XmlSchema.Read() method. I keep getting The 'nillable' attribute is not supported in this context Here is a simple code in C# XmlSchema schema = null; using (StreamReader reader = new StreamReader(<Path to Schema file name>) { schema = XmlSchema.Read(reader.BaseStream, null); } Below is the schema <xs:schema xmlns:b="http://schemas.microsoft.com/BizTalk/2003" xmlns="http://xyz.com.schema.bc.mySchema" attributeFormDefault="unqualified" elementFormDefault="qualified" targetNamespace="http://xyz.com.schema.bc.mySchema" xmlns:xs="http://www.w3.org/2001/XMLSchema"> <xs:element name="data"> <xs:complexType> <xs:sequence> <xs:element name="Component"> <xs:complexType> <xs:sequence> <xs:element minOccurs="1" maxOccurs="unbounded" name="row"> <xs:complexType> <xs:sequence> <xs:element name="changed_by" type="xs:string" nillable="true" /> <xs:element name="column_name" type="xs:string" nillable="true" /> <xs:element name="comment_text" type="xs:string" nillable="true" /> <xs:element name="is_approved" type="xs:string" nillable="true" /> <xs:element name="log_at" type="xs:dateTime" nillable="true" /> <xs:element name="new_val" type="xs:string" nillable="true" /> <xs:element name="old_val" type="xs:string" nillable="true" /> <xs:element name="person_id" type="xs:string" nillable="true" /> <xs:element name="poh_id" type="xs:string" nillable="true" /> <xs:element name="pol_id" type="xs:string" nillable="true" /> <xs:element name="search_name" type="xs:string" nillable="true" /> <xs:element name="unique_id" type="xs:integer" nillable="true" /> </xs:sequence> </xs:complexType> </xs:element> </xs:sequence> </xs:complexType> </xs:element> </xs:complexType> </xs:element> </xs:schema>

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  • Authorizing a computer to access a web application

    - by HackedByChinese
    I have a web application, and am tasked with adding secure sign-on to bolster security, akin to what Google has added to Google accounts. Use Case Essentially, when a user logs in, we want to detect if the user has previously authorized this computer. If the computer has not been authorized, the user is sent a one-time password (via email, SMS, or phone call) that they must enter, where the user may choose to remember this computer. In the web application, we will track authorized devices, allowing users to see when/where they logged in from that device last, and deauthorize any devices if they so choose. We require a solution that is very light touch (meaning, requiring no client-side software installation), and works with Safari, Chrome, Firefox, and IE 7+ (unfortunately). We will offer x509 security, which provides adequate security, but we still need a solution for customers that can't or won't use x509. My intention is to store authorization information using cookies (or, potentially, using local storage, degrading to flash cookies, and then normal cookies). At First Blush Track two separate values (local data or cookies): a hash representing a secure sign-on token, as well as a device token. Both values are driven (and recorded) by the web application, and dictated to the client. The SSO token is dependent on the device as well as a sequence number. This effectively allows devices to be deauthorized (all SSO tokens become invalid) and mitigates replay (not effectively, though, which is why I'm asking this question) through the use of a sequence number, and uses a nonce. Problem With this solution, it's possible for someone to just copy the SSO and device tokens and use in another request. While the sequence number will help me detect such an abuse and thus deauthorize the device, the detection and response can only happen after the valid device and malicious request both attempt access, which is ample time for damage to be done. I feel like using HMAC would be better. Track the device, the sequence, create a nonce, timestamp, and hash with a private key, then send the hash plus those values as plain text. Server does the same (in addition to validating the device and sequence) and compares. That seems much easier, and much more reliable.... assuming we can securely negotiate, exchange, and store private keys. Question So then, how can I securely negotiate a private key for authorized device, and then securely store that key? Is it more possible, at least, if I settle for storing the private key using local storage or flash cookies and just say it's "good enough"? Or, is there something I can do to my original draft to mitigate the vulnerability I describe?

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  • Distinct rand() sequences yielding the same results in an expression

    - by suszterpatt
    Ok, this is a really weird one. I have an MPI program, where each process has to generate random numbers in a fixed range (the range is read from file). What happens is that even though I seed each process with a different value, and the numbers generated by rand() are different in each process, the expression to generate the random numbers still yields the same sequence between them. Here's all relevant code: // 'rank' will be unique for each process int rank; MPI_Comm_rank(MPI_COMM_WORLD, &rank); // seed the RNG with a different value for each process srand(time(NULL) + rank); // print some random numbers to see if we get a unique sequence in each process // 'log' is a uniquely named file, each process has its own log << rand() << " " << rand() << " " << rand() << std::endl; // do boring deterministic stuff while (true) { // waitTimeMin and waitTimeMax are integers, Max is always greater than Min waitSecs = waitTimeMin + rand() % (waitTimeMax - waitTimeMin); log << "waiting " << waitSecs << " seconds" << std::endl; sleep(waitSecs); // do more boring deterministic stuff } Here's the output of each process, with 3 processes generating numbers in the range [1,9]. process 1: 15190 28284 3149 waiting 6 seconds waiting 8 seconds waiting 9 seconds waiting 4 seconds process 2: 286 6264 3153 waiting 6 seconds waiting 8 seconds waiting 9 seconds waiting 4 seconds process 3: 18151 17013 3156 waiting 6 seconds waiting 8 seconds waiting 9 seconds waiting 4 seconds So while rand() clearly generates different numbers, the expression to calculate waitSecs still evaluates to the same sequence on all processes. What's even weirder: if I run the program with the same parameteres again, only the first 3 random numbers will change, the rest of the "random" sequence will be exactly the same in each run! Changing the range of numbers will obviously produce a different result from this one, but the same parameters always yield the same sequence, between processes and between executions: except for the first 3 numbers. Just what the hell is going on here?

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  • Why does JAXB not create a member variable in its generated code when an XML schema base type and subtype have the same element declared in them?

    - by belltower
    I have a question regarding with regard to JAXB generated classes. As you can I see, I have a complex type, DG_PaymentIdentification1, declared in my schema. Its a restriction of PaymentIdentification1. DG_PaymentIdentification1 is also identical to PaymentIdentification1. I also have a type called DG_CreditTransferTransactionInformation10 which has a base type of CreditTransferTransactionInformation10 and is identical to it. I have included the relevant XML schema snippets below. <xs:complexType name="DG_PaymentIdentification1"> <xs:complexContent> <xs:restriction base="PaymentIdentification1"> <xs:sequence> <xs:element name="InstrId" type="DG_Max35Text_REF" minOccurs="0"/> <xs:element name="EndToEndId" type="DG_Max35Text_REF" id="DG-41"/> </xs:sequence> </xs:restriction> </xs:complexContent> </xs:complexType> <xs:complexType name="PaymentIdentification1"> <xs:sequence> <xs:element name="InstrId" type="Max35Text" minOccurs="0"/> <xs:element name="EndToEndId" type="Max35Text"/> </xs:sequence> </xs:complexType> <xs:complexType name="DG_CreditTransferTransactionInformation10"> <xs:complexContent> <xs:restriction base="CreditTransferTransactionInformation10"> <xs:sequence> <xs:element name="PmtId" type="DG_PaymentIdentification1"/> <xs:simpleType name="DG_Max35Text_REF"> <xs:restriction base="DG_NotEmpty35"> <xs:pattern value="[\-A-Za-z0-9\+/\?:\(\)\.,'&#x20;]*"/> </xs:restriction> </xs:simpleType> <xs:simpleType name="Max35Text"> <xs:restriction base="xs:string"> <xs:minLength value="1"/> <xs:maxLength value="35"/> </xs:restriction> </xs:simpleType> JAXB generates the following java class for DG_PaymentIdentification1: @XmlAccessorType(XmlAccessType.FIELD) @XmlType(name = "DG_CreditTransferTransactionInformDGion10") public class DGCreditTransferTransactionInformation10 extends CreditTransferTransactionInformation10 { } My question is why doesnt the DGCreditTransferTransactionInformation10 generated class have a variable of type DG_PaymentIdentification1 in the generated code? The base class CreditTransferTransactionInformation10 does have a type PaymentIdentification1 declared in it. Is there any way of ensuring that DGCreditTransferTransactionInformation10 will have a DG_PaymentIdentification1 in it?

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  • Building Visual Studio Setup Projects with TFS 2010 Team Build

    - by Jakob Ehn
    One of the most common complaints from people starting to use Team Build is that is doesn’t support building Microsoft’s own Setup and Deployment project (*.vdproj). When creating a default build definition that compiles a solution containing a setup project, you’ll get the following warning: The project file "MyProject.vdproj" is not supported by MSBuild and cannot be built.   This is what the problem is all about. MSBuild, that is used for compiling your projects, does not understand the proprietary vdproj format defined by Microsoft quite some time ago. Unfortunately there is no sign that this will change in the near future, in fact the setup projects has barely changed at all since they were introduced. VS 2010 brings no new features or improvements hen it comes to the setup projects. VS 2010 does include a limited version of InstallShield which promises to be more MSBuild friendly and with more or less the same features as VS setup projects. I hope to get a closer look at this installer project type soon. But, how do we go about to build a Visual Studio setup project and produce an MSI as part of a Team Build process? Well, since only one application known to man understands the vdproj projects, we will have to installa copy of Visual Studio on the build server. Sad but true. After doing this, we use the Visual Studio command line interface (devenv) to perform the build. In this post I will show how to do this by using the InvokeProcess activity directly in a build workflow template. You’ll want to run build your setup projects after you have successfully compiled the projects.   Install Visual Studio 2010 on the build server(s)   Open your build process template /remember to branch or copy the xaml file before modifying it!)   Locate the Try to Compile the Project activity   Drop an instance of the InvokeProcess activity from the toolbox onto the designer, after the Run MSBuild for Project activity   Drop an instance of the WriteBuildMessage activity inside the Handle Standard Output section. Set the Importance property to Microsoft.TeamFoundation.Build.Client.BuildMessageImportance.High (NB: This is necessary if you want the output from devenv to show up in the build log when running the build with the default verbosity) Set the Message property to stdOutput   Drop an instance of the WriteBuildError activity to the Handle Error Output section Set the Message property to errOutput   Select the InvokeProcess activity and set the values of the parameters to:     The finished workflow should look like this:     This will generate the MSI files, but they won’t be copied to the drop location. This is because we are using devenv and not MSBuild, so we have to do this explicitly   Drop a Sequence activity somewhere after the Copy to Drop location activity.   Create a variable in the Sequence activity of type IEnumerable<String> and call it GeneratedInstallers   Drop a FindMatchingFiles activity in the sequence activity and set the properties to:     Drop a ForEach<String> activity after the FindMatchingFiles activity. Set the Value property to GeneratedInstallers   Drop an InvokeProcess activity inside the ForEach activity.  FileName: “xcopy.exe” Arguments: String.Format("""{0}"" ""{1}""", item, BuildDetail.DropLocation) The Sequence activity should look like this:     Save the build process template and check it in.   Run the build and verify that the MSI’s is built and copied to the drop location.   Note 1: One of the drawback of using devenv like this in a team build is that since all the output from the default compilations is placed in the Binaries folder, the outputs is not avaialable when devenv is invoked, which causes the whole solution to rebuild again. In TFS 2008, this was pretty simple to fix by using the CustomizableOutDir property. In TFS 2010, the same feature is not avaialble. Jim Lamb blogged about this recently, have a look at it if you have a problem with this: http://blogs.msdn.com/jimlamb/archive/2010/04/13/customizableoutdir-in-tfs-2010.aspx   Note 2: Although the above solution works, a better approach is to wrap this in a custom activity that you can use in your builds. I will come back to this in a future post.

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  • Exploring packages in code

    In my previous post Searching for tasks with code you can see how to explore the control flow side of packages, drilling down through containers, task, and event handlers, but it didn’t cover the data flow. I recently saw a post on the MSDN forum asking how to edit an existing package programmatically, and the sticking point was how to find the the data flow and the components inside. This post builds on some of the previous code and shows how you can explore all objects inside a package. I took the sample Task Search application I’d written previously, and came up with a totally pointless little console application that just walks through the package and writes out the basic type and name of every object it finds, starting with the package itself e.g. Package – MyPackage . The sample package we used last time showed nested objects as well an event handler; a OnPreExecute event tucked away on the task SQL In FEL. The output of this sample tool would look like this: PackageObjects v1.0.0.0 (1.0.0.26627) Copyright (C) 2009 Konesans Ltd Processing File - Z:\Users\Darren Green\Documents\Visual Studio 2005\Projects\SSISTestProject\EventsAndContainersWithExe cSQLForSearch.dtsx Package - EventsAndContainersWithExecSQLForSearch For Loop - FOR Counter Loop Task - SQL In Counter Loop Sequence Container - SEQ For Each Loop Wrapper For Each Loop - FEL Simple Loop Task - SQL In FEL Task - SQL On Pre Execute for FEL SQL Task Sequence Container - SEQ Top Level Sequence Container - SEQ Nested Lvl 1 Sequence Container - SEQ Nested Lvl 2 Task - SQL In Nested Lvl 2 Task - SQL In Nested Lvl 1 #1 Task - SQL In Nested Lvl 1 #2 Connection Manager – LocalHost The code is very similar to what we had previously, but there are a couple of extra bits to deal with connections and to look more closely at a task and see if it is a Data Flow task. For connections your just examine the package's Connections collection as shown in the abridged snippets below. First you can see the call to the ProcessConnections method, followed by the method itself. // Load the package file Application application = new Application(); using (Package package = application.LoadPackage(filename, null)) { // Write out the package name Console.WriteLine("Package - {0}", package.Name); ... More ... // Look and the connections ProcessConnections(package.Connections); } private static void ProcessConnections(Connections connections) { foreach (ConnectionManager connectionManager in connections) { Console.WriteLine("Connection Manager - {0}", connectionManager.Name); } } What we didn’t see in the sample output above was anything to do with the Data Flow, but rest assured the code now handles it too. The following snippet shows how each task is examined to see if it is a Data Flow task, and if so we can then loop through all of the components inside the data flow. private static void ProcessTaskHost(TaskHost taskHost) { if (taskHost == null) { return; } Console.WriteLine("Task - {0}", taskHost.Name); // Check if the task is a Data Flow task MainPipe pipeline = taskHost.InnerObject as MainPipe; if (pipeline != null) { ProcessPipeline(pipeline); } } private static void ProcessPipeline(MainPipe pipeline) { foreach (IDTSComponentMetaData90 componentMetadata in pipeline.ComponentMetaDataCollection) { Console.WriteLine("Pipeline Component - {0}", componentMetadata.Name); // If you wish to make changes to the component then you should really use the managed wrapper. // CManagedComponentWrapper wrapper = componentMetadata.Instantiate(); // wrapper.SetComponentProperty("PropertyName", "Value"); } } Hopefully you can see how we get a reference to the Data Flow task, and then use the ComponentMetaDataCollection to find out what components we have inside the pipeline. If you wanted to know more about the component you could look at the ObjectType or ComponentClassID properties. After that it gets a bit harder and you should get a reference to the wrapper object as the comment suggest and start using the properties, just like you would in the create packages samples, see our Code Development category for some for these examples. Download Sample code project PackageObjects.zip (5KB)

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  • Exploring packages in code

    In my previous post Searching for tasks with code you can see how to explore the control flow side of packages, drilling down through containers, task, and event handlers, but it didn’t cover the data flow. I recently saw a post on the MSDN forum asking how to edit an existing package programmatically, and the sticking point was how to find the the data flow and the components inside. This post builds on some of the previous code and shows how you can explore all objects inside a package. I took the sample Task Search application I’d written previously, and came up with a totally pointless little console application that just walks through the package and writes out the basic type and name of every object it finds, starting with the package itself e.g. Package – MyPackage . The sample package we used last time showed nested objects as well an event handler; a OnPreExecute event tucked away on the task SQL In FEL. The output of this sample tool would look like this: PackageObjects v1.0.0.0 (1.0.0.26627) Copyright (C) 2009 Konesans Ltd Processing File - Z:\Users\Darren Green\Documents\Visual Studio 2005\Projects\SSISTestProject\EventsAndContainersWithExe cSQLForSearch.dtsx Package - EventsAndContainersWithExecSQLForSearch For Loop - FOR Counter Loop Task - SQL In Counter Loop Sequence Container - SEQ For Each Loop Wrapper For Each Loop - FEL Simple Loop Task - SQL In FEL Task - SQL On Pre Execute for FEL SQL Task Sequence Container - SEQ Top Level Sequence Container - SEQ Nested Lvl 1 Sequence Container - SEQ Nested Lvl 2 Task - SQL In Nested Lvl 2 Task - SQL In Nested Lvl 1 #1 Task - SQL In Nested Lvl 1 #2 Connection Manager – LocalHost The code is very similar to what we had previously, but there are a couple of extra bits to deal with connections and to look more closely at a task and see if it is a Data Flow task. For connections your just examine the package's Connections collection as shown in the abridged snippets below. First you can see the call to the ProcessConnections method, followed by the method itself. // Load the package file Application application = new Application(); using (Package package = application.LoadPackage(filename, null)) { // Write out the package name Console.WriteLine("Package - {0}", package.Name); ... More ... // Look and the connections ProcessConnections(package.Connections); } private static void ProcessConnections(Connections connections) { foreach (ConnectionManager connectionManager in connections) { Console.WriteLine("Connection Manager - {0}", connectionManager.Name); } } What we didn’t see in the sample output above was anything to do with the Data Flow, but rest assured the code now handles it too. The following snippet shows how each task is examined to see if it is a Data Flow task, and if so we can then loop through all of the components inside the data flow. private static void ProcessTaskHost(TaskHost taskHost) { if (taskHost == null) { return; } Console.WriteLine("Task - {0}", taskHost.Name); // Check if the task is a Data Flow task MainPipe pipeline = taskHost.InnerObject as MainPipe; if (pipeline != null) { ProcessPipeline(pipeline); } } private static void ProcessPipeline(MainPipe pipeline) { foreach (IDTSComponentMetaData90 componentMetadata in pipeline.ComponentMetaDataCollection) { Console.WriteLine("Pipeline Component - {0}", componentMetadata.Name); // If you wish to make changes to the component then you should really use the managed wrapper. // CManagedComponentWrapper wrapper = componentMetadata.Instantiate(); // wrapper.SetComponentProperty("PropertyName", "Value"); } } Hopefully you can see how we get a reference to the Data Flow task, and then use the ComponentMetaDataCollection to find out what components we have inside the pipeline. If you wanted to know more about the component you could look at the ObjectType or ComponentClassID properties. After that it gets a bit harder and you should get a reference to the wrapper object as the comment suggest and start using the properties, just like you would in the create packages samples, see our Code Development category for some for these examples. Download Sample code project PackageObjects.zip (5KB)

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  • Strings in .NET are Enumerable

    - by Scott Dorman
    It seems like there is always some confusion concerning strings in .NET. This is both from developers who are new to the Framework and those that have been working with it for quite some time. Strings in the .NET Framework are represented by the System.String class, which encapsulates the data manipulation, sorting, and searching methods you most commonly perform on string data. In the .NET Framework, you can use System.String (which is the actual type name or the language alias (for C#, string). They are equivalent so use whichever naming convention you prefer but be consistent. Common usage (and my preference) is to use the language alias (string) when referring to the data type and String (the actual type name) when accessing the static members of the class. Many mainstream programming languages (like C and C++) treat strings as a null terminated array of characters. The .NET Framework, however, treats strings as an immutable sequence of Unicode characters which cannot be modified after it has been created. Because strings are immutable, all operations which modify the string contents are actually creating new string instances and returning those. They never modify the original string data. There is one important word in the preceding paragraph which many people tend to miss: sequence. In .NET, strings are treated as a sequence…in fact, they are treated as an enumerable sequence. This can be verified if you look at the class declaration for System.String, as seen below: // Summary:// Represents text as a series of Unicode characters.public sealed class String : IEnumerable, IComparable, IComparable<string>, IEquatable<string> The first interface that String implements is IEnumerable, which has the following definition: // Summary:// Exposes the enumerator, which supports a simple iteration over a non-generic// collection.public interface IEnumerable{ // Summary: // Returns an enumerator that iterates through a collection. // // Returns: // An System.Collections.IEnumerator object that can be used to iterate through // the collection. IEnumerator GetEnumerator();} As a side note, System.Array also implements IEnumerable. Why is that important to know? Simply put, it means that any operation you can perform on an array can also be performed on a string. This allows you to write code such as the following: string s = "The quick brown fox";foreach (var c in s){ System.Diagnostics.Debug.WriteLine(c);}for (int i = 0; i < s.Length; i++){ System.Diagnostics.Debug.WriteLine(s[i]);} If you executed those lines of code in a running application, you would see the following output in the Visual Studio Output window: In the case of a string, these enumerable or array operations return a char (System.Char) rather than a string. That might lead you to believe that you can get around the string immutability restriction by simply treating strings as an array and assigning a new character to a specific index location inside the string, like this: string s = "The quick brown fox";s[2] = 'a';   However, if you were to write such code, the compiler will promptly tell you that you can’t do it: This preserves the notion that strings are immutable and cannot be changed once they are created. (Incidentally, there is no built in way to replace a single character like this. It can be done but it would require converting the string to a character array, changing the appropriate indexed location, and then creating a new string.)

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