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  • Data Synchronization in mobile apps - multiple devices, multiple users

    - by ProgrammerNewbie
    I'm looking into building my first mobile app. One of the core features of the application is that multiple devices/users will have access to the same data -- and all of them will have CRUD rights. I believe the architecture should involve a central server where all the data is stored. The devices will use an API to interact with the server to perform its data operations (e.g. adding a record, editing a record, deleting a record). I imagine a scenario where synchronizing the data will become a problem. Assume the application should work when it is not connected to the Internet, and thus cannot communicate with this central server. So: User A is offline and edits record #100 User B is offline and edits record #100 User C is offline and deletes record #100 User C goes online (presumably, record #100 should get deleted on the server) User A and B goes online, but the records they edited no longer exist All sorts of scenarios similar to the above can come up. How is this generally handled? I plan to use MySQL, but am wondering if it's not appropriate for such a problem.

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  • data source does not support server-side data paging uisng asp.net Csharp

    - by Aamir Hasan
    Yesterday some one mail me and ask about data source does not support server side data paging.So i write the the solution here please if you have got this problem read this article and see the example code this will help you a Lot.The only change you have to do is in the DataBind().Here you have used the SqlDataReader to read data retrieved from the database, but SqlDataReader is forward only. You can not traverse back and forth on it.So the solution for this is using DataAdapter and DataSet.So your function may change some what like this private void DataBind(){//for grid viewSqlCommand cmdO;string SQL = "select * from TABLE ";conn.Open();cmdO = new SqlCommand(SQL, conn);SqlDataAdapter da = new SqlDataAdapter(cmdO);DataSet ds = new DataSet();da.Fill(ds);GridView1.Visible = true;GridView1.DataSource = ds;GridView1.DataBind();ds.Dispose();da.Dispose();conn.Close();} This surely works. The reset of your code is fine. Enjoy coding.

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  • Recommend .NET data access layer/middle tier

    - by Simon G
    Hi, I'm currently creating an MVC application that will likely to expand to include a silverlight, wpf and possible windows phone all using the same data. So I've created a class library to keep all my objects in and I've created the MVC app. My question is what would be the best way to access the data? Taking into account possible expansion in the future. Should I use web services/WCF? RIA Services? Remoting? Or something else. What have people used in the past and what do you recommend? Thanks

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  • Is Master Data Management CRM's Secret Sauce?

    - by divya.malik
    This was the title of a recent blog entry by our colleagues in EMEA. Having a good master data management system enables organizations to get a unified, accurate and complete understanding of their customers. Gartner Group's John Radcliffe explains why MDM is destined to be at the heart of future CRM and social CRM projects. Experts are predicting big things for master data management (MDM) in the immediate future. While far from being a new kid on the block, its potential benefits at a time when organisations are drowning in data mean that it is in the right place at the right time. "MDM is not 'nice to have'," explains John Radcliffe, research vice president at Gartner. "If tackled in the right way it can provide near term business value that plays into an organisation's new focus on cost efficiencies, risk management and regulatory compliance, while supporting growth and future transformative strategies." The complete article can be found here.

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  • T-SQL Tuesday #006: Tiger/Line Spatial Data

    - by Mike C
    This month’s T-SQL Tuesday post is about LOB data http://sqlblog.com/blogs/michael_coles/archive/2010/05/03/t-sql-tuesday-006-what-about-blob.aspx . For this one I decided to post a sample Tiger/Line SQL database I use all the time in live demos. For those who aren't familiar with it, Tiger/Line data is a dataset published by the U.S. Census Bureau . Tiger/Line has a lot of nice detailed geospatial data down to a very detailed level. It actually goes from the U.S. state level all the way down to...(read more)

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  • how to dinamically add controls in asp.net Dynamic Data

    - by loviji
    Hello, i'm trying to work with asp.NET Dynamic Data. So, I see Dynamic Data not well learned by people as other technologies. now, to my question. Lets us work with Details.aspx page that located on ~\DynamicData\PageTemplates I need to add <asp:DynamicControl runat="server" to page into Form1.detailsTable. i've tried like this: protected DynamicControl myC=new DynamicControl(); protected void Page_Load(object sender, EventArgs e) { foreach(var c in table.Columns) { myC.DataField=c.DisplayName; FormView1.Controls.Add(myC); } } but I can not see the desired result. where is the problem. thanks

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  • Import and Export data from SQL Server 2005 to XL Sheet

    - by SAMIR BHOGAYTA
    For uploading the data from Excel Sheet to SQL Server and viceversa, we need to create a linked server in SQL Server. Expample linked server creation: Before you executing the below command the excel sheet should be created in the specified path and it should contain the name of the columns. EXEC sp_addlinkedserver 'ExcelSource2', 'Jet 4.0', 'Microsoft.Jet.OLEDB.4.0', 'C:\Srinivas\Vdirectory\Testing\Marks.xls', NULL, 'Excel 5.0' Once you executed above query it will crate linked server in SQL Server 2005. The following are the Query from sending the data from Excel sheet to SQL Server 2005. INSERT INTO emp SELECT * from OPENROWSET('Microsoft.Jet.OLEDB.4.0', 'Excel 8.0;Database=C:\text.xls','SELECT * FROM [sheet1$]') The following query is for sending the data from SQL Server 2005 to Excel Sheet. insert into OPENROWSET('Microsoft.Jet.OLEDB.4.0', 'Excel 8.0;Database=c:\text.xls;', 'SELECT * FROM [sheet1$]') select * from emp

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  • POX return data from WCF Data Services

    - by keithwarren7
    I am using WCF Data Services (netfx4) to provide data sourced from SQL via EF, the standard OData mechanism is fine and JSON works as well but I need a third option for generic POX (plain old xml). I have yet to come across a simple strategy or switch that allows me to control this but I am sure one must exist or a workaround method might be available. Any ideas? Ideally I would like to be able to use something like the JSONP option wherein I append 'format=JSON' to the URL, in this case 'format=pox' or 'POX=true' or something of that nature.

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  • Data structure: sort and search effectively

    - by Jiten Shah
    I need to have a data structure with say 4 keys . I can sort on any of these keys. What data structure can I opt for? Sorting time should be very little. I thought of a tree, but it will be only help searching on one key. For other keys I'll have to remake the tree on that particular key and then find it. Is there any data structure that can take care of all 4 keys at the same time? these 4 fields are of total 12 bytes and total size for each record - 40 bytes.. have memory constraints too... operations are : insertion, deletion, sorting on different keys.

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  • How to dynamically add controls in asp.net Dynamic Data

    - by loviji
    Hello, i'm trying to work with asp.NET Dynamic Data. So, I see asp.NET Dynamic Data not well learned by people as other technologies. now, to my question. Lets us work with Details.aspx page that located on ~\DynamicData\PageTemplates I need to add <asp:DynamicControl runat="server" to page into Form1.detailsTable. i've tried like this: protected DynamicControl myC=new DynamicControl(); protected void Page_Load(object sender, EventArgs e) { foreach(var c in table.Columns) { myC.DataField=c.DisplayName; FormView1.Controls.Add(myC); } } but I can not see the desired result. where is the problem. thanks

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  • Deleted Partition Recovery

    - by ankur.trapasiya
    Recently i was installing ubuntu 12.04 on my system. There were 4 partitions on my system and i selected one of the four partition for the installation and chose the option of re sizing the partition. Initially my partition was of size 100+GB and i created another partition out of it of size 15GB (EXT4). Now the moment i changed this partition structure my original partition got lost along with its data and i am left with 50GB partition and 50GB unallocated free space. Now the data that i have lost is meant a lot to me and i want to recover that data. So is there any way i can recover it ? And i haven't checked "format" option while resizing the partition. Thanks in advance.

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  • Fast set indexing data structure for superset retrieval

    - by Asterios
    I am given a set of sets: {{a,b}, {a,b,c}, {a,c}, {a,c,f}} I would like to have a data structure to index those sets such that the following "lookup" is executed fast: find all supersets of a given set. For example, given the set {a,c} the structure would return {{a,b,c}, {a,c,f}, {a,c}} but not {a,b}. Any suggestions? Could this be done with a smart trie-like data structure storing sets after a proper sorting? This data structures is going to be queried a lot. Thus, I'm searching for a structure that might be expensive in build but rather fast to query.

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  • Recovering data from hard disk after an accidental Ubuntu reinstallation

    - by Saurabh Agarwal
    My computer got wiped accidentally due to a fresh Ubuntu installation. Since the drive contains very important data and codes, it would be really great if the same could be recovered. It is a 2TB hard drive which had Ubuntu 10.10 earlier. It now has a Ubuntu 12.04 installed on it (which I understand occupies ~4GB). The machine has been powered off since. The installation was done using a usb with the option where the previous ubuntu installation is removed. Since installation doesn't take a lot of time, I'm inclined to think that the disk wasn't completely formatted and that most of the data is still there. I have no experience with recovery and hence a detailed explanation is very helpful. NOTE: I can arrange an additional 2TB hard disk for copying data. My computer has a fast internet connection and I have other computers connected to the network which I may use to access the previous one as well.

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  • Out-Of-Memory while doing Core Data migration

    - by Kamchatka
    Hello, I'm migrating a CoreData model between two versions of an application. I was storing binary data as blobs in the previous version and I want to take them out of the blobs for performance. My issue is that during the migration it seems that Core Data loads everything into memory which leads to Low Memory Warnings and then to my app being killed. Apple documentation suggests the following : http://developer.apple.com/library/mac/documentation/Cocoa/Conceptual/CoreDataVersioning/Articles/vmCustomizingTheProcess.html#//apple_ref/doc/uid/TP40005510-SW9 However, it seems to rely on the fact that the large objects are applied different mapping. In my case, all the objects are basically the same and the same mapping has to be applied to each of them. I don't see in this case how I could apply their technique. How should I handle a migration with very large objects ?

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  • Serializing Data Structures in C

    - by src
    I've recently read three separate books on algorithms and data structures, tcp/ip socket programming, and programming with memory. The book about memory briefly discussed the topic of serializing data structures for the purposes of storing it to disk, or sending it across a network. I can't help but wonder why the the other two books didn't discuss serialization at all. After an unsuccessful web/book search I'm left wondering where I can find a good book/paper/tutorial on serializing data structures in C? Where or how did you learn it?

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  • How to expose an entity via alternate keys with spring data rest

    - by dan carter
    Spring-data-rest does a great job exposing entities via their primary key for GET, PUT and DELETE etc. operations. /myentityies/123 It also exposes search operations. /myentities/search/byMyOtherKey?myOtherKey=123 In my case the entities have a number of alternate keys. The systems calling us, will know the objects by these IDs, rather than our internal primary key. Is it possible to expose the objects via another URL and have the GET, PUT and DELETE handled by the built-in spring-data-rest controllers? /myentities/myotherkey/456 We'd like to avoid forcing the calling systems to have to make two requests for each update. I've tried playing with @RestResource path value, but there doesn't seem to be a way to add additional paths.

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  • Data structure supporting the following operations

    - by 500865
    I'm looking for a data structure for working with a set of data which is most efficient to do the following : Check whether an item has been categorized or not. (The categorized and uncategorized set are disjoint sets). Get the category of an item. Get all the items in a particular category. Get all the uncategorized items. Remove a particular item from the data set. I was thinking of having a Dictionary<String, Set<String>> to hold all the items in a given category, but that doesn't solve 2.

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  • UPOS RFIDScanner data format

    - by Robert Snyder
    A lot of work that I do currently is based in the OPOS/UPOS world. My company has a device that can read 13.56Mhz tags (RFID), Smart Cards, and Mag Stripe cards. Up until somewhat recently I have only been working with RFID for a very specific scenario. That was to read UltraLight C and Desfire cards. These cards were all setup very specifically so that I could take the data read from those cards and force it into a MSR track2 format. The past couple of weeks, however, I have been working on reading RFID credit cards (since I have a Visa card I've been using mine), and Smart Card credit cards. (The visa card I have has both) In learning how to communicate with SmartCard and reading ISO7816 and EMVCO documents I became a little more familiar with how info is stored. But now I have a question regarding UPOS. The RFID data on my Visa is stored (and read) very similar to how the data is stored and read from the Smart Card on my Visa. Cool. Well in the UPOS spec for SmartCardRW the ReadData method returns a byte array. That's cool, I can just return all that data and then parse it as my heart desires. The RFID though has a LinkedList of Tags. Well this makes sense in terms of my Visa card (reminds me of a question I have in regards to SmartCard, but that is for another question) but what about ULC and Desfire, or for that matter any Mifare card. Pages, Files, Purses don't exactly fit the Tag profile. For instance lets just say I read pages 4-12 on my ULC card. Each page I read is 4 bytes long. Does this mean I have 9 tags in my LinkedList? Is my Tag id the page number? Or then how does that translate to Desfire? I open application 123456 and read file 1 and file 2, Do I have 2 tags? and if so what is my tag id? At least with my Visa I think that I have to use the Tag id (ex 5F24 for my expiration date) and value of {0x15, 0x10, 0x31} Part of me says yes..that makes sense. Another part of me says, "well if that is the case then why doesn't SmartCardRW have Tags?" So that is my question. How do I format my data from those different types of media? or is that the job of my Control Object (the application)? Is so how does it know? The only protocols I have are: // Summary: // Enumerates the available predefined RFID tag protocols the device supports. [Flags] public enum RFIDProtocols { EpcClass0 = 1, RFIDSdt0Plus = 2, EpcClass1 = 4, EpcClass1Gen2 = 8, EpcClass2 = 16, Iso14443A = 4096, Iso14443B = 8192, Iso15693 = 12288, Iso180006B = 16384, Other = 16777216, All = 1073741824, } If I use that well all of my cards that I have are all Iso14443A. I use the ATQA and the SAK to know what type of card I really have. There is no RFID property that lets me specify that. So I'm lost.

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  • Integrating WIF with WCF Data Services

    - by cibrax
    A time ago I discussed how a custom REST Starter kit interceptor could be used to parse a SAML token in the Http Authorization header and wrap that into a ClaimsPrincipal that the WCF services could use. The thing is that code was initially created for Geneva framework, so it got deprecated quickly. I recently needed that piece of code for one of projects where I am currently working on so I decided to update it for WIF. As this interceptor can be injected in any host for WCF REST services, also represents an excellent solution for integrating claim-based security into WCF Data Services (previously known as ADO.NET Data Services). The interceptor basically expects a SAML token in the Authorization header. If a token is found, it is parsed and a new ClaimsPrincipal is initialized and injected in the WCF authorization context. public class SamlAuthenticationInterceptor : RequestInterceptor {   SecurityTokenHandlerCollection handlers;   public SamlAuthenticationInterceptor()     : base(false)   {     this.handlers = FederatedAuthentication.ServiceConfiguration.SecurityTokenHandlers;   }   public override void ProcessRequest(ref RequestContext requestContext)   {     SecurityToken token = ExtractCredentials(requestContext.RequestMessage);     if (token != null)     {       ClaimsIdentityCollection claims = handlers.ValidateToken(token);       var principal = new ClaimsPrincipal(claims);       InitializeSecurityContext(requestContext.RequestMessage, principal);     }     else     {       DenyAccess(ref requestContext);     }   }   private void DenyAccess(ref RequestContext requestContext)   {     Message reply = Message.CreateMessage(MessageVersion.None, null);     HttpResponseMessageProperty responseProperty = new HttpResponseMessageProperty() { StatusCode = HttpStatusCode.Unauthorized };     responseProperty.Headers.Add("WWW-Authenticate",           String.Format("Basic realm=\"{0}\"", ""));     reply.Properties[HttpResponseMessageProperty.Name] = responseProperty;     requestContext.Reply(reply);     requestContext = null;   }   private SecurityToken ExtractCredentials(Message requestMessage)   {     HttpRequestMessageProperty request = (HttpRequestMessageProperty)  requestMessage.Properties[HttpRequestMessageProperty.Name];     string authHeader = request.Headers["Authorization"];     if (authHeader != null && authHeader.Contains("<saml"))     {       XmlTextReader xmlReader = new XmlTextReader(new StringReader(authHeader));       var col = SecurityTokenHandlerCollection.CreateDefaultSecurityTokenHandlerCollection();       SecurityToken token = col.ReadToken(xmlReader);                                        return token;     }     return null;   }   private void InitializeSecurityContext(Message request, IPrincipal principal)   {     List<IAuthorizationPolicy> policies = new List<IAuthorizationPolicy>();     policies.Add(new PrincipalAuthorizationPolicy(principal));     ServiceSecurityContext securityContext = new ServiceSecurityContext(policies.AsReadOnly());     if (request.Properties.Security != null)     {       request.Properties.Security.ServiceSecurityContext = securityContext;     }     else     {       request.Properties.Security = new SecurityMessageProperty() { ServiceSecurityContext = securityContext };      }    }    class PrincipalAuthorizationPolicy : IAuthorizationPolicy    {      string id = Guid.NewGuid().ToString();      IPrincipal user;      public PrincipalAuthorizationPolicy(IPrincipal user)      {        this.user = user;      }      public ClaimSet Issuer      {        get { return ClaimSet.System; }      }      public string Id      {        get { return this.id; }      }      public bool Evaluate(EvaluationContext evaluationContext, ref object state)      {        evaluationContext.AddClaimSet(this, new DefaultClaimSet(System.IdentityModel.Claims.Claim.CreateNameClaim(user.Identity.Name)));        evaluationContext.Properties["Identities"] = new List<IIdentity>(new IIdentity[] { user.Identity });        evaluationContext.Properties["Principal"] = user;        return true;      }    } A WCF Data Service, as any other WCF Service, contains a service host where this interceptor can be injected. The following code illustrates how that can be done in the “svc” file. <%@ ServiceHost Language="C#" Debug="true" Service="ContactsDataService"                 Factory="AppServiceHostFactory" %> using System; using System.ServiceModel; using System.ServiceModel.Activation; using Microsoft.ServiceModel.Web; class AppServiceHostFactory : ServiceHostFactory {    protected override ServiceHost CreateServiceHost(Type serviceType, Uri[] baseAddresses)   {     WebServiceHost2 result = new WebServiceHost2(serviceType, true, baseAddresses);     result.Interceptors.Add(new SamlAuthenticationInterceptor());                 return result;   } } WCF Data Services includes an specific WCF host of out the box (DataServiceHost). However, the service is not affected at all if you replace it with a custom one as I am doing in the code above (WebServiceHost2 is part of the REST Starter kit). Finally, the client application needs to pass the SAML token somehow to the data service. In case you are using any Http client library for consuming the data service, that’s easy to do, you only need to include the SAML token as part of the “Authorization” header. If you are using the auto-generated data service proxy, a little piece of code is needed to inject a SAML token into the DataServiceContext instance. That class provides an event “SendingRequest” that any client application can leverage to include custom code that modified the Http request before it is sent to the service. So, you can easily create an extension method for the DataServiceContext that negotiates the SAML token with an existing STS, and adds that token as part of the “Authorization” header. public static class DataServiceContextExtensions {        public static void ConfigureFederatedCredentials(this DataServiceContext context, string baseStsAddress, string realm)   {     string address = string.Format(STSAddressFormat, baseStsAddress, realm);                  string token = NegotiateSecurityToken(address);     context.SendingRequest += (source, args) =>     {       args.RequestHeaders.Add("Authorization", token);     };   } private string NegotiateSecurityToken(string address) { } } I left the NegociateSecurityToken method empty for this extension as it depends pretty much on how you are negotiating tokens from an existing STS. In case you want to end-to-end REST solution that involves an Http endpoint for the STS, you should definitely take a look at the Thinktecture starter STS project in codeplex.

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  • How to disable authentication schemes for WCF Data Services

    - by Schneider
    When I deployed my WCF Data Services to production hosting I started to get the following error (or similar depending on which auth schemes are active): IIS specified authentication schemes 'Basic, Anonymous', but the binding only supports specification of exactly one authentication scheme. Valid authentication schemes are Digest, Negotiate, NTLM, Basic, or Anonymous. Change the IIS settings so that only a single authentication scheme is used. Apparently WCF Data Services (WCF in general?) cannot handle having more than once authentication scheme active. OK so I am aware that I can disable all-but-one authentication scheme on the web application via IIS control panel .... via a support request!! Is there a way to specify a single authentication scheme on a per-service level in the web.config? I thought this might be as straight forward as making a change to <system.serviceModel> but... it turns out that WCF Data Services do not configure themselves in the web config. If you look at the DataService<> class it does not implement a [ServiceContract] hence you cannot refer to it in the <service><endpoint>...which I presume would be needed for changing its configuration via XML. P.S. Our host is using II6, but both solutions for IIS6 & IIS7 appreciated.

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  • Correctly assigning value to a Core Data attribute with an integer data-type

    - by Gordon Fontenot
    I'm missing something here, and feeling like an idiot about it. I'm using a UIPickerView in my app, and I need to assign the row number to a 32-bit integer attribute for a Core Data object. To do this, I am using this method: -(void)pickerView:(UIPickerView *)pickerView didSelectRow:(NSInteger)row inComponent:(NSInteger)component { object.integerValue = row; } This is giving me a warning: warning: passing argument 1 of 'setIntegerValue:' makes pointer from integer without a cast What am I mixing up here? --Edit 1-- Ok, so I can get rid of the warning by changing the method to do the following: NSNumber *number = [NSNumber numberWithInteger:row]; object.integerValue = rating; However, I still get a value of 0 for object.integerValue if I use NSLog to print it out. object.integerValue has a max value of 5, so I print out number instead, and then I'm getting a number above 62,000,000. Which doesn't seem right to me, since there are 5 rows. If I NSLog the row variable, I get a number between 0 and 5. So why do I end up with a completely different number after casting the number to NSNumber? --Edit 2-- Ok, so I'm realizing that there is some fundamental idea that I don't understand. I now understand that the 60 million + number can be cast back to the correct 0-5 number by using integerValue. So, it seems my question is how can I save an integer between 0-5 to the attribute if the NSNumber that is returned is over 60 million? Do I need to be using a different data type?

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  • Doubts About Core Data NSManagedObject Deep Copy

    - by Jigzat
    Hello everyone, I have a situation where I must copy one NSManagedObject from the main context into an editing context. It sounds unnecessary to most people as I have seen in similar situations described in Stackoverflow but I looks like I need it. In my app there are many views in a tab bar and every view handles different information that is related to the other views. I think I need multiple MOCs since the user may jump from tab to tab and leave unsaved changes in some tab but maybe it saves data in some other tab/view so if that happens the changes in the rest of the views are saved without user consent and in the worst case scenario makes the app crash. For adding new information I got away by using an adding MOC and then merging changes in both MOCs but for editing is not that easy. I saw a similar situation here in Stackoverflow but the app crashes since my data model doesn't seem to use NSMutableSet for the relationships (I don't think I have a many-to-many relationship, just one-to-many) I think it can be modified so I can retrieve the relationships as if they were attributes for (NSString *attr in relationships) { [cloned setValue:[source valueForKey:attr] forKey:attr]; } but I don't know how to merge the changes of the cloned and original objects. I think I could just delete the object from the main context, then merge both contexts and save changes in the main context but I don't know if is the right way to do it. I'm also concerned about database integrity since I'm not sure that the inverse relationships will keep the same reference to the cloned object as if it were the original one. Can some one please enlighten me about this?

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  • Binding Data to a TextBlock using Domain Data Source

    - by TFisher
    I have a map with hotspots for each state (done in Expression Blend). I capture each MouseEnter of the state (1 thru 50). I pass that into my Domain Data Source: Dim activebox As Path = TryCast(sender, Path) activebox.Fill = mouseOverColor Dim StateID As Integer = CInt(Right(activebox.Name, 2)) Dim _StateContext As New StateContext myDataGrid.ItemsSource = _StateContext.States _StateContext.Load(_StateContext.GetStateByStateIDQuery(StateID.Text)) The above works fine for a datagrid, listbox and even a dataform. But I created a popup with a stackpanel that has textblocks. popupStatesBox.DataContext = ?????????????? popupStatesBox.IsOpen = True 'popup does open but has no data -- popupStatesBox.xaml <Popup x:Name="popupStatsBox" Margin="8,35,0,8" DataContext="{Binding}" IsOpen="false" Width="268" HorizontalAlignment="Left"> <StackPanel x:Name="Layout" Background="Black"> <TextBlock x:Name="tbState" Text="{Binding StateName /> <TextBlock x:Name="tbAbbrev" Text="{Binding Abbreviation}" /> </StackPanel> </Popup> How do I get the textblocks to display the values from the _StateContext. StackPanel has DataContext but no ItemsSource. What am I missing?

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  • Design suggestion for expression tree evaluation with time-series data

    - by Lirik
    I have a (C#) genetic program that uses financial time-series data and it's currently working but I want to re-design the architecture to be more robust. My main goals are: sequentially present the time-series data to the expression trees. allow expression trees to access previous data rows when needed. to optimize performance of the data access while evaluating the expression trees. keep a common interface so various types of data can be used. Here are the possible approaches I've thought about: I can evaluate the expression tree by passing in a data row into the root node and let each child node use the same data row. I can evaluate the expression tree by passing in the data row index and letting each node get the data row from a shared DataSet (currently I'm passing the row index and going to multiple synchronized arrays to get the data). Hybrid: an immutable data set is accessible by all of the expression trees and each expression tree is evaluated by passing in a data row. The benefit of the first approach is that the data row is being passed into the expression tree and there is no further query done on the data set (which should increase performance in a multithreaded environment). The drawback is that the expression tree does not have access to the rest of the data (in case some of the functions need to do calculations using previous data rows). The benefit of the second approach is that the expression trees can access any data up to the latest data row, but unless I specify what that row is, I'll have to iterate through the rows and figure out which one is the last one. The benefit of the hybrid is that it should generally perform better and still provide access to the earlier data. It supports two basic "views" of data: the latest row and the previous rows. Do you guys know of any design patterns or do you have any tips that can help me build this type of system? Should I use a DataSet to hold and present the data, or are there more efficient ways to present rows of data while maintaining a simple interface? FYI: All of my code is written in C#.

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  • Data Warehouse: Modelling a future schedule

    - by Pat
    I'm creating a DW that will contain data on financial securities such as bonds and loans. These securities are associated with payment schedules. For example, a bond could pay quarterly, while a mortage would usually pay monthly (sometimes biweekly). The payment schedule is created when the security is traded and, in the majority of cases, will remain unchanged. However, the design would need to accomodate those cases where it does change. I'm currently attempting to model this data and I'm having difficulty coming up with a workable design. One of the most commonly queried fields is "next payment date". Users often want to know when a security will pay next. Therefore, I want to make it as easy as possible for them to get the next payment date and amount for each security. Also, users often run historical queries in which case they'd want the next payment date and amount as of a specific point in time. For example, they may want to look back at 1/31/09 and query the next payment dates (which would usually be in February 2009 for mortgages). It's also common that they want to query a security's entire payment schedule, which might consist of 360 records (30 year mortgage x 12 payments/year). Since the next payment date and amount would be changing each month or even biweekly, these fields wouldn't seem to fit into a slow-changing dimension very well. It would probably make more sense to use a fact table, but I'm unsure of how to model it. Any ideas would be greatly appreciated.

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