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• WPF Border DesiredHeight

  - by Joseph Sturtevant

  The following Microsoft example code contains the following: <Grid> ... <Border Name="Content" ... > ... </Border> </Grid> <ControlTemplate.Triggers> <Trigger Property="IsExpanded" Value="True"> <Setter TargetName="ContentRow" Property="Height" Value="{Binding ElementName=Content,Path=DesiredHeight}" /> </Trigger> ... </ControlTemplate.Triggers> When run, however, this code generates the following databinding error: System.Windows.Data Error: 39 : BindingExpression path error: 'DesiredHeight' property not found on 'object' ''Border' (Name='Content')'. BindingExpression:Path=DesiredHeight; DataItem='Border' (Name='Content'); target element is 'RowDefinition' (HashCode=2034711); target property is 'Height' (type 'GridLength') Despite this error, the code works correctly. I have looked through the documentation and DesiredHeight does not appear to be a member of Border. Can anyone explain where DesiredHeight is coming from? Also, is there any way to resolve/suppress this error so my program output is clean?

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• When should I be cautious using data binding in .NET?

  - by Ben McCormack

  I just started working on a small team of .NET programmers about a month ago and recently got in a discussion with our team lead regarding why we don't use databinding at all in our code. Every time we work with a data grid, we iterate through a data table and populate the grid row by row; the code usually looks something like this: Dim dt as DataTable = FuncLib.GetData("spGetTheData ...") Dim i As Integer For i = 0 To dt.Rows.Length - 1 '(not sure why we do not use a for each here)' gridRow = grid.Rows.Add() gridRow(constantProductID).Value = dt("ProductID").Value gridRow(constantProductDesc).Value = dt("ProductDescription").Value Next '(I am probably missing something in the code, but that is basically it)' Our team lead was saying that he got burned using data binding when working with Sheridan Grid controls, VB6, and ADO recordsets back in the nineties. He's not sure what the exact problem was, but he remembers that binding didn't work as expected and caused him some major problems. Since then, they haven't trusted data binding and load the data for all their controls by hand. The reason the conversation even came up was because I found data binding to be very simple and really liked separating the data presentation (in this case, the data grid) from the in-memory data source (in this case, the data table). "Loading" the data row by row into the grid seemed to break this distinction. I also observed that with the advent of XAML in WPF and Silverlight, data-binding seems like a must-have in order to be able to cleanly wire up a designer's XAML code with your data. When should I be cautious of using data-binding in .NET?

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• How to make a WPF ComboBox editable with custom values

  - by Liam

  I would like to have a combobox that allows selection from a list of values and also allow a custom value from the typed in text. For display reasons the items are a complex type (lets say the combobox item template displays a patch of color and a flag indicating if it is a custom color). public class ColorLevel { public decimal Intensity { get; set; } public bool IsCustom { get; set; } public Color BaseColor { get; set; } public override ToString() { return string.Format("{0}", Intensity*100); } } Example items var items = new [] { new ColorLevel { Intensity = 0.9m, IsCustom = false, BaseColor = Color.Red }, new ColorLevel { Intensity = 0.7m, IsCustom = false, BaseColor = Color.Red } } XAML <ComboBox SelectedItem="{Binding Path=SelectedColorLevel}" IsEditable="true" IsTextSearchEnabled="true"> </ComboBox> So the above markup works when an item is selected from the item list. And as you type with the text search the matching items are selected. If the typed text doesn't match an item then the SelectedColorLevel is set to null. The question is at what point (and how) is it best to create a new custom item that can be set to the SelectedColorLevel when the typed text doesn't match an item. For example I would want to assign a new item to the selected value such as new ColorLevel { Intensity = decimal.Parse(textvalue), IsCustom = true } or using an appropriate converter and databinding to the Text property.

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• How to update a custom dependency property when the datasource list changes

  - by John

  Hi We have a user control with a custom dependency property (DP). The DP is bound to an ObservableCollection. When a new item is added to the collection programatically, the databinding does not update the target DP. Why? We think it's because, unfortunately, in our case the target is not a ListBox or ListView, but a Canvas. The DP, when changed or initialized, is supposed to draw a Shape (!) onto the Canvas, and the shape's position and size is bound to the collection item's two properties: WIDTH, LEFT. Ideally we don't want to clear the Canvas and redraw all items just becasue one has been added (or deleted). But how? So: How can the custom DP take care of drawing the shape for the new collection item? What callback do we need, at what point in time does this have to happen, and what specific MetaDataOptions might there? Also, are there any good resources out there concerning all these dependency property options. They are quite confusing. MSDN does not really help with what we're trying to do. Thanks!

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• How can I bind a List as ItemSource to ListView in XAML?

  - by Jonas

  I'm learning WPF and would like to have a collection similar to a LinkedList, to where I can add and remove strings. And I want to have a ListView that listen to that collection with databinding. How can I do bind a simple list collection to a ListView in XAML? My idea (not working) is something like this: <Window x:Class="TestApp.MainWindow" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" Title="MainWindow" Height="350" Width="525"> <Window.Resources> <LinkedList x:Key="myList"></LinkedList> //Wrong <Window.Resources> <Grid> <ListView Height="100" HorizontalAlignment="Left" Margin="88,134,0,0" Name="listView1" VerticalAlignment="Top" Width="120" ItemsSource="{Binding Source={StaticResource myList}}"/> //Wrong </Grid> </Window> All my code (updated version, not working): <Window x:Class="TestApp.MainWindow" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" Title="MainWindow" Height="350" Width="525"> <Grid> <TextBox Height="23" HorizontalAlignment="Left" Margin="12,12,0,0" Name="textBox1" VerticalAlignment="Top" Width="120" /> <Button Content="Button" Height="23" HorizontalAlignment="Right" Margin="0,12,290,0" Name="button1" VerticalAlignment="Top" Width="75" Click="button1_Click" /> <ListView Height="100" HorizontalAlignment="Left" Margin="88,134,0,0" Name="listView1" VerticalAlignment="Top" Width="120" ItemsSource="{Binding myList}"/> </Grid> </Window> C#-code: namespace TestApp { public partial class MainWindow : Window { ObservableCollection<string> myList = new ObservableCollection<string>(); public MainWindow() { InitializeComponent(); myList.Add("first string"); } private void button1_Click(object sender, RoutedEventArgs e) { myList.Add(textBox1.Text); textBox1.Text = myList.Count+"st"; } } }

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• Bing Maps - Auto update location binding of pushpins

  - by abp

  Hi I'm using the Bing Maps control to display a series of custom pushpins, representing objects which are constantly moving around and changing state. Using databinding the various properties for the objects are being updated as they should, but for some reason this doesn't apply to their locations. I have the map bound to an ObservableCollection as such: <UserControl.Resources> <DataTemplate x:Key="PushpinTemplate"> <v:CustomPushpin /> </DataTemplate> </UserControl.Resources> ... <m:Map Name="map"> <m:MapItemsControl ItemTemplate="{StaticResource PushpinTemplate}" ItemsSource="{Binding Objects}" /> </m:Map> ...and in CustomPushpin: <UserControl ... m:MapLayer.Position="{Binding Location}" m:MapLayer.PositionOrigin="BottomCenter" mc:Ignorable="d" d:DesignHeight="126" d:DesignWidth="85"> Like all other properties, the Location of the individual objects are implemented using INotifyPropertyChanged. private Location _location; public Location Location { get { return _location; } set { _location = value; OnPropertyChanged("Location"); } } When the map is moving, either because of panning or zooming, the objects move, but othersize not. I can't quite figure if I'm doing something wrong here, or if it's a problem with the Bing Maps control. Any thought?

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• Black Magic in Grails Data Binding!?

  - by Tiago Alves

  As described in http://n4.nabble.com/Grails-Data-Binding-for-One-To-Many-Relationships-with-REST-tp1754571p1754571.html i'm trying to automatically bind my REST data. I understand now that for one-to-many associations the map that is required for the data binding must have a list of ids of the many side such as: [propName: propValue, manyAssoc: [1, 2]] However, I'm getting this exception Executing action [save] of controller [com.example.DomainName] caused exception: org.springframework.orm.hibernate3.HibernateSystemException: IllegalArgumentException occurred calling getter of com.example.DomainName.id; nested exception is org.hibernate.PropertyAccessException: IllegalArgumentException occurred calling getter of com.example.DomainName.id However, even weirder is the update action that is generated for the controller. There we have the databinding like this: domainObjectInstance.properties = params['domainObject'] But, and this is the really weird thing, params['domainObject'] is null! It is null because all the domainObject fields are passed directly in the params map itself. If I change the above line to domainObjectInstance.properties = null the domainObject is still updated! Why is this happening and more important, how can I bind my incoming XML automatically if it comes in this format (the problem is the one-to-many associations): <product> <name>Table</name> <brand id="1" /> <categories> <category id="1" /> <category id="2" /> </categories> </product>

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• Databound Label text displays old data upon save. Re-open record and data is correct?

  - by Mike Hestness

  I have a windows forms application. I have a main form and I have a button on this form to set a "Qualified" date/time stamp. I have a Databound label control that I set the value when the user clicks the button. This date/time stamp is working as far as displaying but when you click the save button it either shows blank or the previous date/time. If you then then close the record and re-open it the new date/time value is displayed so the data is getting to the database it's just not persisting in the dataset as new data?? Not sure why the databinding isn't refreshing the value. I have noticed this behavior even if I use a textbox, same thing if I do it programatically. If I manually type in a value it persists?? Here is the code I'm using in the click event of my button: string result = string.Empty; string jobOrderID = UnitOfWork.MasterDSBS.MJOBO[0].JC_IDNO.ToString(); string timeNow = DateTime.Now.ToString(); //Call Web service to make the update RadServices.Service1 rsWeb = new RadServices.Service1(); result = rsWeb.SetQualifiedDate(timeNow, jobOrderID ); //Changed the qualified label text. _btnQualify.Text = "Qualified"; rlQualifiedDate.Text = timeNow;

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• Elfsign Object Signing on Solaris

  - by danx

  Elfsign Object Signing on Solaris Don't let this happen to you—use elfsign! Solaris elfsign(1) is a command that signs and verifies ELF format executables. That includes not just executable programs (such as ls or cp), but other ELF format files including libraries (such as libnvpair.so) and kernel modules (such as autofs). Elfsign has been available since Solaris 10 and ELF format files distributed with Solaris, since Solaris 10, are signed by either Sun Microsystems or its successor, Oracle Corporation. When an ELF file is signed, elfsign adds a new section the ELF file, .SUNW_signature, that contains a RSA public key signature and other information about the signer. That is, the algorithm used, algorithm OID, signer CN/OU, and time stamp. The signature section can later be verified by elfsign or other software by matching the signature in the file agains the ELF file contents (excluding the signature). ELF executable files may also be signed by a 3rd-party or by the customer. This is useful for verifying the origin and authenticity of executable files installed on a system. The 3rd-party or customer public key certificate should be installed in /etc/certs/ to allow verification by elfsign. For currently-released versions of Solaris, only cryptographic framework plugin libraries are verified by Solaris. However, all ELF files may be verified by the elfsign command at any time. Elfsign Algorithms Elfsign signatures are created by taking a digest of the ELF section contents, then signing the digest with RSA. To verify, one takes a digest of ELF file and compares with the expected digest that's computed from the signature and RSA public key. Originally elfsign took a MD5 digest of a SHA-1 digest of the ELF file sections, then signed the resulting digest with RSA. In Solaris 11.1 then Solaris 11.1 SRU 7 (5/2013), the elfsign crypto algorithms available have been expanded to keep up with evolving cryptography. The following table shows the available elfsign algorithms: Elfsign Algorithm Solaris Release Comments elfsign sign -F rsa_md5_sha1   S10, S11.0, S11.1 Default for S10. Not recommended* elfsign sign -F rsa_sha1 S11.1 Default for S11.1. Not recommended elfsign sign -F rsa_sha256 S11.1 patch SRU7+   Recommended ___ *Most or all CAs do not accept MD5 CSRs and do not issue MD5 certs due to MD5 hash collision problems. RSA Key Length. I recommend using RSA-2048 key length with elfsign is RSA-2048 as the best balance between a long expected "life time", interoperability, and performance. RSA-2048 keys have an expected lifetime through 2030 (and probably beyond). For details, see Recommendation for Key Management: Part 1: General, NIST Publication SP 800-57 part 1 (rev. 3, 7/2012, PDF), tables 2 and 4 (pp. 64, 67). Step 1: create or obtain a key and cert The first step in using elfsign is to obtain a key and cert from a public Certificate Authority (CA), or create your own self-signed key and cert. I'll briefly explain both methods. Obtaining a Certificate from a CA To obtain a cert from a CA, such as Verisign, Thawte, or Go Daddy (to name a few random examples), you create a private key and a Certificate Signing Request (CSR) file and send it to the CA, following the instructions of the CA on their website. They send back a signed public key certificate. The public key cert, along with the private key you created is used by elfsign to sign an ELF file. The public key cert is distributed with the software and is used by elfsign to verify elfsign signatures in ELF files. You need to request a RSA "Class 3 public key certificate", which is used for servers and software signing. Elfsign uses RSA and we recommend RSA-2048 keys. The private key and CSR can be generated with openssl(1) or pktool(1) on Solaris. Here's a simple example that uses pktool to generate a private RSA_2048 key and a CSR for sending to a CA: $ pktool gencsr keystore=file format=pem outcsr=MYCSR.p10 \ subject="CN=canineswworks.com,OU=Canine SW object signing" \ outkey=MYPRIVATEKEY.key $ openssl rsa -noout -text -in MYPRIVATEKEY.key Private-Key: (2048 bit) modulus: 00:d2:ef:42:f2:0b:8c:96:9f:45:32:fc:fe:54:94: . . . [omitted for brevity] . . . c9:c7 publicExponent: 65537 (0x10001) privateExponent: 26:14:fc:49:26:bc:a3:14:ee:31:5e:6b:ac:69:83: . . . [omitted for brevity] . . . 81 prime1: 00:f6:b7:52:73:bc:26:57:26:c8:11:eb:6c:dc:cb: . . . [omitted for brevity] . . . bc:91:d0:40:d6:9d:ac:b5:69 prime2: 00:da:df:3f:56:b2:18:46:e1:89:5b:6c:f1:1a:41: . . . [omitted for brevity] . . . f3:b7:48:de:c3:d9:ce:af:af exponent1: 00:b9:a2:00:11:02:ed:9a:3f:9c:e4:16:ce:c7:67: . . . [omitted for brevity] . . . 55:50:25:70:d3:ca:b9:ab:99 exponent2: 00:c8:fc:f5:57:11:98:85:8e:9a:ea:1f:f2:8f:df: . . . [omitted for brevity] . . . 23:57:0e:4d:b2:a0:12:d2:f5 coefficient: 2f:60:21:cd:dc:52:76:67:1a:d8:75:3e:7f:b0:64: . . . [omitted for brevity] . . . 06:94:56:d8:9d:5c:8e:9b $ openssl req -noout -text -in MYCSR.p10 Certificate Request: Data: Version: 2 (0x2) Subject: OU=Canine SW object signing, CN=canineswworks.com Subject Public Key Info: Public Key Algorithm: rsaEncryption Public-Key: (2048 bit) Modulus: 00:d2:ef:42:f2:0b:8c:96:9f:45:32:fc:fe:54:94: . . . [omitted for brevity] . . . c9:c7 Exponent: 65537 (0x10001) Attributes: Signature Algorithm: sha1WithRSAEncryption b3:e8:30:5b:88:37:68:1c:26:6b:45:af:5e:de:ea:60:87:ea: . . . [omitted for brevity] . . . 06:f9:ed:b4 Secure storage of RSA private key. The private key needs to be protected if the key signing is used for production (as opposed to just testing). That is, protect the key to protect against unauthorized signatures by others. One method is to use a PIN-protected PKCS#11 keystore. The private key you generate should be stored in a secure manner, such as in a PKCS#11 keystore using pktool(1). Otherwise others can sign your signature. Other secure key storage mechanisms include a SCA-6000 crypto card, a USB thumb drive stored in a locked area, a dedicated server with restricted access, Oracle Key Manager (OKM), or some combination of these. I also recommend secure backup of the private key. Here's an example of generating a private key protected in the PKCS#11 keystore, and a CSR. $ pktool setpin # use if PIN not set yet Enter token passphrase: changeme Create new passphrase: Re-enter new passphrase: Passphrase changed. $ pktool gencsr keystore=pkcs11 label=MYPRIVATEKEY \ format=pem outcsr=MYCSR.p10 \ subject="CN=canineswworks.com,OU=Canine SW object signing" $ pktool list keystore=pkcs11 Enter PIN for Sun Software PKCS#11 softtoken: Found 1 asymmetric public keys. Key #1 - RSA public key: MYPRIVATEKEY Here's another example that uses openssl instead of pktool to generate a private key and CSR: $ openssl genrsa -out cert.key 2048 $ openssl req -new -key cert.key -out MYCSR.p10 Self-Signed Cert You can use openssl or pktool to create a private key and a self-signed public key certificate. A self-signed cert is useful for development, testing, and internal use. The private key created should be stored in a secure manner, as mentioned above. The following example creates a private key, MYSELFSIGNED.key, and a public key cert, MYSELFSIGNED.pem, using pktool and displays the contents with the openssl command. $ pktool gencert keystore=file format=pem serial=0xD06F00D lifetime=20-year \ keytype=rsa hash=sha256 outcert=MYSELFSIGNED.pem outkey=MYSELFSIGNED.key \ subject="O=Canine Software Works, OU=Self-signed CA, CN=canineswworks.com" $ pktool list keystore=file objtype=cert infile=MYSELFSIGNED.pem Found 1 certificates. 1. (X.509 certificate) Filename: MYSELFSIGNED.pem ID: c8:24:59:08:2b:ae:6e:5c:bc:26:bd:ef:0a:9c:54:de:dd:0f:60:46 Subject: O=Canine Software Works, OU=Self-signed CA, CN=canineswworks.com Issuer: O=Canine Software Works, OU=Self-signed CA, CN=canineswworks.com Not Before: Oct 17 23:18:00 2013 GMT Not After: Oct 12 23:18:00 2033 GMT Serial: 0xD06F00D0 Signature Algorithm: sha256WithRSAEncryption $ openssl x509 -noout -text -in MYSELFSIGNED.pem Certificate: Data: Version: 3 (0x2) Serial Number: 3496935632 (0xd06f00d0) Signature Algorithm: sha256WithRSAEncryption Issuer: O=Canine Software Works, OU=Self-signed CA, CN=canineswworks.com Validity Not Before: Oct 17 23:18:00 2013 GMT Not After : Oct 12 23:18:00 2033 GMT Subject: O=Canine Software Works, OU=Self-signed CA, CN=canineswworks.com Subject Public Key Info: Public Key Algorithm: rsaEncryption Public-Key: (2048 bit) Modulus: 00:bb:e8:11:21:d9:4b:88:53:8b:6c:5a:7a:38:8b: . . . [omitted for brevity] . . . bf:77 Exponent: 65537 (0x10001) Signature Algorithm: sha256WithRSAEncryption 9e:39:fe:c8:44:5c:87:2c:8f:f4:24:f6:0c:9a:2f:64:84:d1: . . . [omitted for brevity] . . . 5f:78:8e:e8 $ openssl rsa -noout -text -in MYSELFSIGNED.key Private-Key: (2048 bit) modulus: 00:bb:e8:11:21:d9:4b:88:53:8b:6c:5a:7a:38:8b: . . . [omitted for brevity] . . . bf:77 publicExponent: 65537 (0x10001) privateExponent: 0a:06:0f:23:e7:1b:88:62:2c:85:d3:2d:c1:e6:6e: . . . [omitted for brevity] . . . 9c:e1:e0:0a:52:77:29:4a:75:aa:02:d8:af:53:24: c1 prime1: 00:ea:12:02:bb:5a:0f:5a:d8:a9:95:b2:ba:30:15: . . . [omitted for brevity] . . . 5b:ca:9c:7c:19:48:77:1e:5d prime2: 00:cd:82:da:84:71:1d:18:52:cb:c6:4d:74:14:be: . . . [omitted for brevity] . . . 5f:db:d5:5e:47:89:a7:ef:e3 exponent1: 32:37:62:f6:a6:bf:9c:91:d6:f0:12:c3:f7:04:e9: . . . [omitted for brevity] . . . 97:3e:33:31:89:66:64:d1 exponent2: 00:88:a2:e8:90:47:f8:75:34:8f:41:50:3b:ce:93: . . . [omitted for brevity] . . . ff:74:d4:be:f3:47:45:bd:cb coefficient: 4d:7c:09:4c:34:73:c4:26:f0:58:f5:e1:45:3c:af: . . . [omitted for brevity] . . . af:01:5f:af:ad:6a:09:bf Step 2: Sign the ELF File object By now you should have your private key, and obtained, by hook or crook, a cert (either from a CA or use one you created (a self-signed cert). The next step is to sign one or more objects with your private key and cert. Here's a simple example that creates an object file, signs, verifies, and lists the contents of the ELF signature. $ echo '#include <stdio.h>\nint main(){printf("Hello\\n");}'>hello.c $ make hello cc -o hello hello.c $ elfsign verify -v -c MYSELFSIGNED.pem -e hello elfsign: no signature found in hello. $ elfsign sign -F rsa_sha256 -v -k MYSELFSIGNED.key -c MYSELFSIGNED.pem -e hello elfsign: hello signed successfully. format: rsa_sha256. signer: O=Canine Software Works, OU=Self-signed CA, CN=canineswworks.com. signed on: October 17, 2013 04:22:49 PM PDT. $ elfsign list -f format -e hello rsa_sha256 $ elfsign list -f signer -e hello O=Canine Software Works, OU=Self-signed CA, CN=canineswworks.com $ elfsign list -f time -e hello October 17, 2013 04:22:49 PM PDT $ elfsign verify -v -c MYSELFSIGNED.key -e hello elfsign: verification of hello failed. format: rsa_sha256. signer: O=Canine Software Works, OU=Self-signed CA, CN=canineswworks.com. signed on: October 17, 2013 04:22:49 PM PDT. Signing using the pkcs11 keystore To sign the ELF file using a private key in the secure pkcs11 keystore, replace "-K MYSELFSIGNED.key" in the "elfsign sign" command line with "-T MYPRIVATEKEY", where MYPRIVATKEY is the pkcs11 token label. Step 3: Install the cert and test on another system Just signing the object isn't enough. You need to copy or install the cert and the signed ELF file(s) on another system to test that the signature is OK. Your public key cert should be installed in /etc/certs. Use elfsign verify to verify the signature. Elfsign verify checks each cert in /etc/certs until it finds one that matches the elfsign signature in the file. If one isn't found, the verification fails. Here's an example: $ su Password: # rm /etc/certs/MYSELFSIGNED.key # cp MYSELFSIGNED.pem /etc/certs # exit $ elfsign verify -v hello elfsign: verification of hello passed. format: rsa_sha256. signer: O=Canine Software Works, OU=Self-signed CA, CN=canineswworks.com. signed on: October 17, 2013 04:24:20 PM PDT. After testing, package your cert along with your ELF object to allow elfsign verification after your cert and object are installed or copied. Under the Hood: elfsign verification Here's the steps taken to verify a ELF file signed with elfsign. The steps to sign the file are similar except the private key exponent is used instead of the public key exponent and the .SUNW_signature section is written to the ELF file instead of being read from the file. Generate a digest (SHA-256) of the ELF file sections. This digest uses all ELF sections loaded in memory, but excludes the ELF header, the .SUNW_signature section, and the symbol table Extract the RSA signature (RSA-2048) from the .SUNW_signature section Extract the RSA public key modulus and public key exponent (65537) from the public key cert Calculate the expected digest as follows:     signaturepublicKeyExponent % publicKeyModulus Strip the PKCS#1 padding (most significant bytes) from the above. The padding is 0x00, 0x01, 0xff, 0xff, . . ., 0xff, 0x00. If the actual digest == expected digest, the ELF file is verified (OK). Further Information elfsign(1), pktool(1), and openssl(1) man pages. "Signed Solaris 10 Binaries?" blog by Darren Moffat (2005) shows how to use elfsign. "Simple CLI based CA on Solaris" blog by Darren Moffat (2008) shows how to set up a simple CA for use with self-signed certificates. "How to Create a Certificate by Using the pktool gencert Command" System Administration Guide: Security Services (available at docs.oracle.com)

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• Class design issue

  - by user2865206

  I'm new to OOP and a lot of times I become stumped in situations similar to this example: Task: Generate an XML document that contains information about a person. Assume the information is readily available in a database. Here is an example of the structure: <Person> <Name>John Doe</Name> <Age>21</Age> <Address> <Street>100 Main St.</Street> <City>Sylvania</City> <State>OH</State> </Address> <Relatives> <Parents> <Mother> <Name>Jane Doe</Name> </Mother> <Father> <Name>John Doe Sr.</Name> </Father> </Parents> <Siblings> <Brother> <Name>Jeff Doe</Name> </Brother> <Brother> <Name>Steven Doe</Name> </Brother> </Siblings> </Relatives> </Person> Ok lets create a class for each tag (ie: Person, Name, Age, Address) Lets assume each class is only responsible for itself and the elements directly contained Each class will know (have defined by default) the classes that are directly contained within them Each class will have a process() function that will add itself and its childeren to the XML document we are creating When a child is drawn, as in the previous line, we will have them call process() as well Now we are in a recursive loop where each object draws their childeren until all are drawn But what if only some of the tags need to be drawn, and the rest are optional? Some are optional based on if the data exists (if we have it, we must draw it), and some are optional based on the preferences of the user generating the document How do we make sure each object has the data it needs to draw itself and it's childeren? We can pass down a massive array through every object, but that seems shitty doesnt it? We could have each object query the database for it, but thats a lot of queries, and how does it know what it's query is? What if we want to get rid of a tag later? There is no way to reference them. I've been thinking about this for 20 hours now. I feel like I am misunderstanding a design principle or am just approaching this all wrong. How would you go about programming something like this? I suppose this problem could apply to any senario where there are classes that create other classes, but the classes created need information to run. How do I get the information to them in a way that doesn't seem fucky? Thanks for all of your time, this has been kicking my ass.

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• Lifetime issue of IDisposable unmanaged resources in a complex object graph?

  - by stakx

  This question is about dealing with unmanaged resources (COM interop) and making sure there won't be any resource leaks. I'd appreciate feedback on whether I seem to do things the right way. Background: Let's say I've got two classes: A class LimitedComResource which is a wrapper around a COM object (received via some API). There can only be a limited number of those COM objects, therefore my class implements the IDisposable interface which will be responsible for releasing a COM object when it's no longer needed. Objects of another type ManagedObject are temporarily created to perform some work on a LimitedComResource. They are not IDisposable. To summarize the above in a diagram, my classes might look like this: +---------------+ +--------------------+ | ManagedObject | <>------> | LimitedComResource | +---------------+ +--------------------+ | o IDisposable (I'll provide example code for these two classes in just a moment.) Question: Since my temporary ManagedObject objects are not disposable, I obviously have no control over how long they'll be around. However, in the meantime I might have Disposed the LimitedComObject that a ManagedObject is referring to. How can I make sure that a ManagedObject won't access a LimitedComResource that's no longer there? +---------------+ +--------------------+ | managedObject | <>------> | (dead object) | +---------------+ +--------------------+ I've currently implemented this with a mix of weak references and a flag in LimitedResource which signals whether an object has already been disposed. Is there any better way? Example code (what I've currently got): LimitedComResource: class LimitedComResource : IDisposable { private readonly IUnknown comObject; // <-- set in constructor ... void Dispose(bool notFromFinalizer) { if (!this.isDisposed) { Marshal.FinalReleaseComObject(comObject); } this.isDisposed = true; } internal bool isDisposed = false; } ManagedObject: class ManagedObject { private readonly WeakReference limitedComResource; // <-- set in constructor ... public void DoSomeWork() { if (!limitedComResource.IsAlive()) { throw new ObjectDisposedException(); // ^^^^^^^^^^^^^^^^^^^^^^^ // is there a more suitable exception class? } var ur = (LimitedComResource)limitedComResource.Target; if (ur.isDisposed) { throw new ObjectDisposedException(); } ... // <-- do something sensible here! } }

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• What makes the availability of both primitive and object-wrapped values in JavaScript useful?

  - by Delan Azabani

  I wrote a blog post a while ago detailing how the availability of both primitive and object-wrapped value types in JavaScript (for things such as Number, String and Boolean) causes trouble, including but not limited to type-casting to a boolean (e.g. object-wrapped NaN, "" and false actually type-cast to true). My question is, with all this confusion and problems, is there any benefit to JavaScript having both types of values for the built-in classes?

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• How can you make a variable/Object read only in Javascript?

  - by codeninja

  I have an Object that I only want to be defined when constructed. How can I prevent the Object reference from being changed?

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• In java what is the diference between an object and a class?

  - by David

  In java what is the diference between an object and a class? The book i'm working from made it seem as though once a class is created it also exists as an object.

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• In java what is the difference between an object and a class?

  - by David

  In java what is the difference between an object and a class? The book I'm working from made it seem as though once a class is created it also exists as an object.

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• How would I create an object that uses String type behaviour for creation?

  - by Zachary Spencer

  I'd like to be able to create an object that is created like a String object, and when created verifies that the String value is an appropriate option. I.E. SpecificString can be "Bob" or "Jim". SpecificString BadName = "Sam" //Throws exception SpecificString GoodName = "Bob" //Does not throw exception. Is this possible?

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• Object Building in ActionScript

  - by kumar

  I am getting an object structure like Object-- --- Object STRING1:VALUE STRING2:VALUE STRING3:VALUE ---- OBJECT STRING1:VALUE STRING2:VALUE STRING3:VALUE Now I want to filter this object because i need only STRING2:VALUE in the same object structure and need to a an structure similar to: Object STRING2:VALUE Object STRING2:VALUE and I need to do it in runtime can somebody please let me know ..

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• C++ is it possible to set an object to null?

  - by John

  Further in my code, I check to see check if an object is null/empty. Is there a way to set an object to null?

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• Detect when a new property is added to a Javascript object?

  - by UICodes

  A simple example using a built-in javascript object: navigator.my_new_property = "some value"; //can we detect that this new property was added? I don't want to constantly poll the object to check for new properties. Is there some type of higher level setter for objects instead of explicitly stating the property to monitor? Again, I don't want to detect if the property value changed, but rather when a new property is added. Ideas? thanks

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• Best practices for using the Entity Framework with WPF DataBinding

  - by Ken Smith

  I'm in the process of building my first real WPF application (i.e., the first intended to be used by someone besides me), and I'm still wrapping my head around the best way to do things in WPF. It's a fairly simple data access application using the still-fairly-new Entity Framework, but I haven't been able to find a lot of guidance online for the best way to use these two technologies (WPF and EF) together. So I thought I'd toss out how I'm approaching it, and see if anyone has any better suggestions. I'm using the Entity Framework with SQL Server 2008. The EF strikes me as both much more complicated than it needs to be, and not yet mature, but Linq-to-SQL is apparently dead, so I might as well use the technology that MS seems to be focusing on. This is a simple application, so I haven't (yet) seen fit to build a separate data layer around it. When I want to get at data, I use fairly simple Linq-to-Entity queries, usually straight from my code-behind, e.g.: var families = from family in entities.Family.Include("Person") orderby family.PrimaryLastName, family.Tag select family; Linq-to-Entity queries return an IOrderedQueryable result, which doesn't automatically reflect changes in the underlying data, e.g., if I add a new record via code to the entity data model, the existence of this new record is not automatically reflected in the various controls referencing the Linq query. Consequently, I'm throwing the results of these queries into an ObservableCollection, to capture underlying data changes: familyOC = new ObservableCollection<Family>(families.ToList()); I then map the ObservableCollection to a CollectionViewSource, so that I can get filtering, sorting, etc., without having to return to the database. familyCVS.Source = familyOC; familyCVS.View.Filter = new Predicate<object>(ApplyFamilyFilter); familyCVS.View.SortDescriptions.Add(new System.ComponentModel.SortDescription("PrimaryLastName", System.ComponentModel.ListSortDirection.Ascending)); familyCVS.View.SortDescriptions.Add(new System.ComponentModel.SortDescription("Tag", System.ComponentModel.ListSortDirection.Ascending)); I then bind the various controls and what-not to that CollectionViewSource: <ListBox DockPanel.Dock="Bottom" Margin="5,5,5,5" Name="familyList" ItemsSource="{Binding Source={StaticResource familyCVS}, Path=., Mode=TwoWay}" IsSynchronizedWithCurrentItem="True" ItemTemplate="{StaticResource familyTemplate}" SelectionChanged="familyList_SelectionChanged" /> When I need to add or delete records/objects, I manually do so from both the entity data model, and the ObservableCollection: private void DeletePerson(Person person) { entities.DeleteObject(person); entities.SaveChanges(); personOC.Remove(person); } I'm generally using StackPanel and DockPanel controls to position elements. Sometimes I'll use a Grid, but it seems hard to maintain: if you want to add a new row to the top of your grid, you have to touch every control directly hosted by the grid to tell it to use a new line. Uggh. (Microsoft has never really seemed to get the DRY concept.) I almost never use the VS WPF designer to add, modify or position controls. The WPF designer that comes with VS is sort of vaguely helpful to see what your form is going to look like, but even then, well, not really, especially if you're using data templates that aren't binding to data that's available at design time. If I need to edit my XAML, I take it like a man and do it manually. Most of my real code is in C# rather than XAML. As I've mentioned elsewhere, entirely aside from the fact that I'm not yet used to "thinking" in it, XAML strikes me as a clunky, ugly language, that also happens to come with poor designer and intellisense support, and that can't be debugged. Uggh. Consequently, whenever I can see clearly how to do something in C# code-behind that I can't easily see how to do in XAML, I do it in C#, with no apologies. There's been plenty written about how it's a good practice to almost never use code-behind in WPF page (say, for event-handling), but so far at least, that makes no sense to me whatsoever. Why should I do something in an ugly, clunky language with god-awful syntax, an astonishingly bad editor, and virtually no type safety, when I can use a nice, clean language like C# that has a world-class editor, near-perfect intellisense, and unparalleled type safety? So that's where I'm at. Any suggestions? Am I missing any big parts of this? Anything that I should really think about doing differently?

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• Looping through a SimpleXML object, or turning the whole thing into an array.

  - by Coffee Cup

  I'm trying to work out how to iterate though a returned SimpleXML object. I'm using a toolkit called Tarzan AWS, which connects to Amazon Web Services (SimpleDB, S3, EC2, etc). I'm specifically using SimpleDB. I can put data into the Amazon SimpleDB service, and I can get it back. I just don't know how to handle the SimpleXML object that is returned. The Tarzan AWS documentation says this: Look at the response to navigate through the headers and body of the response. Note that this is an object, not an array, and that the body is a SimpleXML object. Here's a sample of the returned SimpleXML object: [body] = SimpleXMLElement Object ( [QueryWithAttributesResult] = SimpleXMLElement Object ( [Item] = Array ( [0] = SimpleXMLElement Object ( [Name] = message12413344443260 [Attribute] = Array ( [0] = SimpleXMLElement Object ( [Name] = active [Value] = 1 ) [1] = SimpleXMLElement Object ( [Name] = user [Value] = john ) [2] = SimpleXMLElement Object ( [Name] = message [Value] = This is a message. ) [3] = SimpleXMLElement Object ( [Name] = time [Value] = 1241334444 ) [4] = SimpleXMLElement Object ( [Name] = id [Value] = 12413344443260 ) [5] = SimpleXMLElement Object ( [Name] = ip [Value] = 10.10.10.1 ) ) ) [1] = SimpleXMLElement Object ( [Name] = message12413346907303 [Attribute] = Array ( [0] = SimpleXMLElement Object ( [Name] = active [Value] = 1 ) [1] = SimpleXMLElement Object ( [Name] = user [Value] = fred ) [2] = SimpleXMLElement Object ( [Name] = message [Value] = This is another message ) [3] = SimpleXMLElement Object ( [Name] = time [Value] = 1241334690 ) [4] = SimpleXMLElement Object ( [Name] = id [Value] = 12413346907303 ) [5] = SimpleXMLElement Object ( [Name] = ip [Value] = 10.10.10.2 ) ) ) ) So what code do I need to get through each of the object items? I'd like to loop through each of them and handle it like a returned mySQL query. For example, I can query SimpleDB and then loop though the SimpleXML so I can display the results on the page. Alternatively, how do you turn the whole shebang into an array? I'm new to SimpleXML, so I apologise if my questions aren't specific enough.

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• C# using the "this" keyword in this situation?

  - by Alex

  Hi, I've completed a OOP course assignment where I design and code a Complex Number class. For extra credit, I can do the following: Add two complex numbers. The function will take one complex number object as a parameter and return a complex number object. When adding two complex numbers, the real part of the calling object is added to the real part of the complex number object passed as a parameter, and the imaginary part of the calling object is added to the imaginary part of the complex number object passed as a parameter. Subtract two complex numbers. The function will take one complex number object as a parameter and return a complex number object. When subtracting two complex numbers, the real part of the complex number object passed as a parameter is subtracted from the real part of the calling object, and the imaginary part of the complex number object passed as a parameter is subtracted from the imaginary part of the calling object. I have coded this up, and I used the this keyword to denote the current instance of the class, the code for my add method is below, and my subtract method looks similar: public ComplexNumber Add(ComplexNumber c) { double realPartAdder = c.GetRealPart(); double complexPartAdder = c.GetComplexPart(); double realPartCaller = this.GetRealPart(); double complexPartCaller = this.GetComplexPart(); double finalRealPart = realPartCaller + realPartAdder; double finalComplexPart = complexPartCaller + complexPartAdder; ComplexNumber summedComplex = new ComplexNumber(finalRealPart, finalComplexPart); return summedComplex; } My question is: Did I do this correctly and with good style? (using the this keyword)?

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• jQuery accessing objects

  - by user1275268

  I'm trying to access the values of an object from a function I created with a callback, but have run into some trouble. I'm still fairly new at jQuery/javascript. I call the function as follows: siteDeps(id,function(data){ $.each(data,function(key,val) { console.log(key); console.log(val); }); }); The function runs 5 ajax queries from XML data and returns data as an multidimensional object; here is a excerpt showing the meat of it: function siteDeps(id,callback) { var result = { sitecontactid : {}, siteaddressid : {}, sitephoneid : {}, contactaddressid : {}, contactphoneid : {} }; ...//.... var url5 = decodeURIComponent("sql2xml.php?query=xxxxxxxxxxx"); $.get(url5, function(data){ $(data).find('ID').each(function(i){ result.delsitephoneid[i] = $(this).text(); }); }); callback(result); } The console.log output shows this: sitecontactid Object 0: "2" 1: "3" __proto__: Object siteaddressid Object 0: "1" __proto__: Object sitephoneid Object 0: "1" 1: "5" 2: "54" __proto__: Object contactaddressid Object 0: "80" __proto__: Object contactphoneid Object 0: "6" __proto__: Object How can I extract the callback data in a format I can use, for instance sitephoneid: "1","5","54" Or is there a better/simpler way to do this? Thanks in advance.

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• Can static methods be called using object/instance in .NET

  Ans is Yes and No   Yes in C++, Java and VB.NET No in C#   This is only compiler restriction in c#. You might see in some websites that we can break this restriction using reflection and delegates, but we can’t, according to my little research J I shall try to explain you…   Following is code sample to break this rule using reflection, it seems that it is possible to call a static method using an object, p1 using System; namespace T {     class Program     {         static void Main()         {             var p1 = new Person() { Name = "Smith" };             typeof(Person).GetMethod("TestStatMethod").Invoke(p1, new object[] { });                     }         class Person         {             public string Name { get; set; }             public static void TestStatMethod()             {                 Console.WriteLine("Hello");             }         }     } } but I do not think so this method is being called using p1 rather Type Name “Person”. I shall try to prove this… look at another example…  Test2 has been inherited from Test1. Let’s see various scenarios… Scenario1 using System; namespace T {     class Program     {         static void Main()         {             Test1 t = new Test1();            typeof(Test2).GetMethod("Method1").Invoke(t,                                  new object[] { });         }     }     class Test1     {         public static void Method1()         {             Console.WriteLine("At test1::Method1");         }     }       class Test2 : Test1     {         public static void Method1()         {             Console.WriteLine("At test1::Method2");         }     } } Output:   At test1::Method2 Scenario2         static void Main()         {             Test2 t = new Test2();            typeof(Test2).GetMethod("Method1").Invoke(t,                                          new object[] { });         }   Output:   At test1::Method2   Scenario3         static void Main()         {             Test1 t = new Test2();            typeof(Test2).GetMethod("Method1").Invoke(t,                             new object[] { });         }   Output: At test1::Method2 In all above scenarios output is same, that means, Reflection also not considering the object what you pass to Invoke method in case of static methods. It is always considering the type which you specify in typeof(). So, what is the use passing instance to “Invoke”. Let see below sample using System; namespace T {     class Program     {         static void Main()         {            typeof(Test2).GetMethod("Method1").                Invoke(null, new object[] { });         }     }       class Test1     {         public static void Method1()         {             Console.WriteLine("At test1::Method1");         }     }     class Test2 : Test1     {         public static void Method1()         {             Console.WriteLine("At test1::Method2");         }     } }   Output is   At test1::Method2   I was able to call Invoke “Method1” of Test2 without any object.  Yes, there no wonder here as Method1 is static. So we may conclude that static methods cannot be called using instances (only in c#) Why Microsoft has restricted it in C#? Ans: Really there Is no use calling static methods using objects because static methods are stateless. but still Java and C++ latest compilers allow calling static methods using instances. Java sample class Test {      public static void main(String str[])      {            Person p = new Person();            System.out.println(p.GetCount());      } }   class Person {   public static int GetCount()   {      return 100;   } }   Output          100 span.fullpost {display:none;}

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• Unity3d: calculate the result of a transform without modifying transform object itself

  - by Heisenbug

  I'm in the following situation: I need to move an object in some way, basically rotating it around its parent local position, or translating it in its parent local space (I know how to do this). The amount of rotation and translation is know at runtime (it depends on several factors, the speed of the object, enviroment factors, etc..). The problem is the following: I can perform this transformation only if the result position of the transformed object fit some criterias. An example could be this: the distance between the position before and after the transformation must be less than a given threshold. (Actually the conditions could be several and more complex) The problem is that if I use Transform.Rotate and Transform.Translate methods of my GameObject, I will loose the original Transform values. I think I can't copy the original Transform using instantiate for performance issues. How can I perform such a task? I think I have more or less 2 possibilities: First Don't modify the GameObject position through Transform. Calculate which will be the position after the transform. If the position is legal, modify transform through Translate and Rotate methods Second Store the original transform someway. Transform the object using Translate and Rotate. If the transformed position is illegal, restore the original one.

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