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  • Are batch mutations atomic in Cassandra?

    - by user317459
    The Cassandra API supports batch mutations: batch_mutate(keyspace, mutation_map, consistency_level): Executes the specified mutations on the keyspace. mutation_map is a map; the outer map maps the key to the inner map, which maps the column family to the Mutation; can be read as: map. To be more specific, the outer map key is a row key, the inner map key is the column family name. A Mutation specifies either columns to insert or columns to delete. See Mutation and Deletion above for more details. Are all mutations that are executed in a batch executed atomically? So if one of the mutations fails, do the others fail too?

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  • Succinct But Complete Example of WPF App?

    - by Eric J.
    Is there a succinct but complete example project or tutorial that brings together the pieces of the Microsoft stack for a complete application? WPF MVVM Business Objects EF Database I find plenty for WPF and plenty for EF, but am having trouble fully understanding how the EF generated classes relate to business objects, and how those business objects in turn fit into the MVVM pattern.

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  • Authentication Problem in Silverlight - Cannot connect to SQL Server

    - by Johann
    Hi All, At the moment, when I try to register a user using the default Business Template in Silverlight, I am getting an error. Basically I am following a tutorial found on Channel 9 on how to build a business app with Silverlight. "An error has occurred while establishing a connection to the server. (provider: Named Pipes Provider, error: 40 – Could not open a connection to SQL Server) (Microsoft SQL Server, Error: 5) An error has occurred while establishing a connection to the server. When connecting to SQL Server 2005, this failure may be caused by the fact that under the default settings SQL Server does not allow remote connections. (provider: Named Pipes Provider, error: 40 – Could not open a connection to SQL Server) (Microsoft SQL Server, Error: 1326)". I found a blog where it identifies the problem, and followed every step, however I am still getting the same problems. Here is my connection string:- <add name="SIEventManagerEntities" connectionString="metadata=res://*/EventManagerDBModel.csdl|res://*/EventManagerDBModel.ssdl|res://*/EventManagerDBModel.msl;provider=System.Data.SqlClient;provider connection string=&quot;Data Source=MONFU-PC;Initial Catalog=SIEventManager;Integrated Security=SSPI;MultipleActiveResultSets=True&quot;" providerName="System.Data.EntityClient" /> Any help would really be very much appreciated! Thanks

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  • Linq query challenge - can this be done?

    - by vdh_ant
    My table structure is as follows: Person 1-M PesonAddress Person 1-M PesonPhone Person 1-M PesonEmail Person 1-M Contract Contract M-M Program Contract M-1 Organization At the end of this query I need a populated object graph where each person has their: PesonAddress's PesonPhone's PesonEmail's PesonPhone's Contract's - and this has its respective Program's Now I had the following query and I thought that it was working great, but it has a couple of problems: from people in ctx.People.Include("PersonAddress") .Include("PersonLandline") .Include("PersonMobile") .Include("PersonEmail") .Include("Contract") .Include("Contract.Program") where people.Contract.Any( contract => (param.OrganizationId == contract.OrganizationId) && contract.Program.Any( contractProgram => (param.ProgramId == contractProgram.ProgramId))) select people; The problem is that it filters the person to the criteria but not the Contracts or the Contract's Programs. It brings back all Contracts that each person has not just the ones that have an OrganizationId of x and the same goes for each of those Contract's Programs respectively. What I want is only the people that have at least one contract with an OrgId of x with and where that contract has a Program with the Id of y... and for the object graph that is returned to have only the contracts that match and programs within that contract that match. I kinda understand why its not working, but I don't know how to change it so it is working... This is my attempt thus far: from people in ctx.People.Include("PersonAddress") .Include("PersonLandline") .Include("PersonMobile") .Include("PersonEmail") .Include("Contract") .Include("Contract.Program") let currentContracts = from contract in people.Contract where (param.OrganizationId == contract.OrganizationId) select contract let currentContractPrograms = from contractProgram in currentContracts let temp = from x in contractProgram.Program where (param.ProgramId == contractProgram.ProgramId) select x where temp.Any() select temp where currentContracts.Any() && currentContractPrograms.Any() select new Person { PersonId = people.PersonId, FirstName = people.FirstName, ..., ...., MiddleName = people.MiddleName, Surname = people.Surname, ..., ...., Gender = people.Gender, DateOfBirth = people.DateOfBirth, ..., ...., Contract = currentContracts, ... }; //This doesn't work But this has several problems (where the Person type is an EF object): I am left to do the mapping by myself, which in this case there is quite a lot to map When ever I try to map a list to a property (i.e. Scholarship = currentScholarships) it says I can't because IEnumerable is trying to be cast to EntityCollection Include doesn't work Hence how do I get this to work. Keeping in mind that I am trying to do this as a compiled query so I think that means anonymous types are out.

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  • How to pass a Lambda Expression as method parameter with EF

    - by Registered User
    How do I pass an EF expression as a method argument? To illustrate my question I have created a pseudo code example: The first example is my method today. The example utilizes EF and a Fancy Retry Logic. What I need to do is to encapsulate the Fancy Retry Logic so that it becomes more generic and does not duplicate. In the second example is how I want it to be, with a helper method that accepts the EF expression as an argument. This would be a trivial thing to do with SQL, but I want to do it with EF so that I can benefit from the strongly typed objects. First Example: public static User GetUser(String userEmail) { using (MyEntities dataModel = new MyEntities ()) { var query = FancyRetryLogic(() => { (dataModel.Users.FirstOrDefault<User>(x => x.UserEmail == userEmail))); }); return query; } } Second Example: T RetryHelper<T>(Expression<Func<T, TValue>> expression) { using (MyEntities dataModel = new (MyEntities ()) { var query = FancyRetryLogic(() => { return dataModel.expression }); } } public User GetUser(String userEmail) { return RetryHelper<User>(<User>.FirstOrDefault<User>(x => x.UserEmail == userEmail)) }

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  • Method return values and exceptions

    - by dnagirl
    I have an interface called iIncident which defines a single method when(). when() should return a DateTime object. I'm trying to decide what to do if $object->when() has no DateTime to return as might be the case just after an object is instantiated and before all its properties are set. My choices are: return false throw some kind of Exception return some default DateTime like '9999-01-01' My inclination is to go with an Exception since $object really can't act as an incident until it knows when it occurred. I don't want to return a default DateTime because it complicates comparisons and it's not true. And I don't really want to return false because then I have to check for it every time I call the method- but if that is the preferred method, I guess I will. Is throwing an exception the best way? And is there a predefined exception type I should use (none of the SPL ones struck me as particularly appropriate- but that might just indicate my lack of experience)?

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  • How big teams work with database

    - by Michael Riva
    Lets say I have a team, 20 developers. And we are making a project on .net. In team every one can easy create their tables according to their modules working on it. And we think to use an ORM, can you tell me how can and which ORM tools for good to working with team. Is there any proven way? I m asking becouse I never work with a team, so I dont know the best practices. So you guys what kind of pattern you use?. I realy wonder. The team members can write their unit tests and supply necessary design patterns. What kind of approach I need to create to manage team? What kind of ORM tools that we have to use?

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  • Assigning a variable of a struct that contains an instance of a class to another variable

    - by xport
    In my understanding, assigning a variable of a struct to another variable of the same type will make a copy. But this rule seems broken as shown on the following figure. Could you explain why this happened? using System; namespace ReferenceInValue { class Inner { public int data; public Inner(int data) { this.data = data; } } struct Outer { public Inner inner; public Outer(int data) { this.inner = new Inner(data); } } class Program { static void Main(string[] args) { Outer p1 = new Outer(1); Outer p2 = p1; Console.WriteLine("p1:{0}, p2:{1}", p1.inner.data, p2.inner.data); p1.inner.data = 2; Console.WriteLine("p1:{0}, p2:{1}", p1.inner.data, p2.inner.data); p2.inner.data = 3; Console.WriteLine("p1:{0}, p2:{1}", p1.inner.data, p2.inner.data); Console.ReadKey(); } } }

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  • How to design this simple database?

    - by Vafello
    I have 2 tables - one storing user information (id, username, password) and the second one storing information about events (id, name, description, date, username(represents the user who created the event)). I would like to implement 'favourite events' functionality. This would allow the user to store his favourite events and later display them in a list. I am not sure how to implement this in terms of design. I need a simple solution. Something like storing the IDs of favourite events in a field in the user table. I am using mysql and php. Can anyone point me to the right direction?

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  • multiple return values from PHP with jQuery AJAX

    - by benhowdle89
    I'm using this jQuery code: $.ajax ({ type: "POST", url: "customerfilter.php", data: dataString, cache: false, success: function(html) { $(".custName").html(html); } }); How can i do something like this: $(".projDesc").html(html1); So i can split the returned results into two html elements? echo "<p>" .$row['cust_name']. "</p>"; thats the PHP i'm using and i want to echo another statement which i can put into another HTML element Does this make sense?

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  • How to accomplish covariant return types when returning a shared_ptr?

    - by Kyle
    using namespace boost; class A {}; class B : public A {}; class X { virtual shared_ptr<A> foo(); }; class Y : public X { virtual shared_ptr<B> foo(); }; The return types aren't covariant (nor are they, therefore, legal), but they would be if I was using raw pointers instead. What's the commonly accepted idiom to work around this, if there is one?

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  • Filter list as a parameter in a compiled query

    - by JK
    I have the following compiled query that I want to return a list of "groups" that don't have a "GroupID" that's contained in a filtered list: CompiledQuery.Compile(ConfigEntities contexty, List list) = from c in context.Groups where (!csList.Contains(c.GroupID)) select c).ToList() However I'm getting the following run-time error: The specified parameter 'categories' of type 'System.Collections.Generic.List`1[[System.Int32, mscorlib, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c261364e126]]' is not valid. Only scalar parameters (such as Int32, Decimal, and Guid) are supported. Any ideas?

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  • EF4 Code-First CTP5 Many-to-one

    - by Kevin McKelvin
    I've been trying to get EF4 CTP5 to play nice with an existing database, but struggling with some basic mapping issues. I have two model classes so far: public class Job { [Key, Column(Order = 0)] public int JobNumber { get; set; } [Key, Column(Order = 1)] public int VersionNumber { get; set; } public virtual User OwnedBy { get; set; } } and [Table("Usernames")] public class User { [Key] public string Username { get; set; } public string EmailAddress { get; set; } public bool IsAdministrator { get; set; } } And I have my DbContext class exposing those as IDbSet I can query my users, but as soon as I added the OwnedBy field to the Job class I began getting this error in all my tests for the Jobs: Invalid column name 'UserUsername'. I want this to behave like NHibernate's many-to-one, whereas I think EF4 is treating it as a complex type. How should this be done?

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  • convert a sql statement to class?

    - by walter
    Is there a tool or code to convert a sql statement to class? Something like: Dim sqlText = "SELECT CustomerID, Name, Address, City FROM dbo.Customer WHERE CustomerID = 1" Dim obj As New ***SqlStatementTool***(sqlText) obj.GetTables() 'Will Return Tables in sqlText obj.GetWheres() 'Will Return conditions in sqltext obj.GetParameters() 'will return parameters in sqltext

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  • Not loading the object caused EF4 (code first) to remove the relationship

    - by Lavinski
    Firstly this is a EF4: Code First - Property Loading question. I'm loading an object like so var item = Context.Table.Find( update.Identifier ); This object has a property Relationship so a table has a Relationship object. Now i'm updating my item but my Relationship object is not toched (and therefore not lazy loaded). Now here's the problem .. I save my item and my relationship to the Relationship object is deleted, apparently the model thinks i set it to null. However it all works if I look at the property before saving. So I'm looking into LoadProperty or doing a query and using Include. Has anyone else come across this issue and how did you get around it?

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  • How to provide default argument as this object?

    - by atch
    I would like to have declaration like this: void Date::get_days_name(const Date& = this) which I would understand that if no argument is provided use this object as an argument. For some reason in VS I'm getting err msg: 'Error 1 error C2355: 'this' : can only be referenced inside non-static member ' Any idea what I'm doing wrong?

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  • LinkDemand error on webserver when using TrackSource

    - by robertpnl
    Hi, On a webserver (shared hosting provider) I published a website with a ADO.Net Framework model in use with MySql Connector 6.3.1. When I request a page, a Security Exception will be happen with this error messages: "LinkDemand The type of the first permission that failed was: System.Security.Permissions.SecurityPermission The Zone of the assembly that failed was: MyComputer ". This exception raised when code collect the listeners of a tracksource: public class MySqlTrace { private static TraceSource source = new TraceSource("mysql"); static MySqlTrace() { foreach (TraceListener listener in source.Listeners) // <-- Exception throw here { // ... } } } The web.config doesn't have any trace data or system.diagnostics. My question is, why will a get a LinkDemand security exception during collecting the source listeners. What can maybe be wrong in here?

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  • Redeclaration of parameters

    - by Scott
    While looking through the Selenium source code I noticed the following in the PageFactory: public static <T> T initElements(WebDriver driver, Class<T> pageClassToProxy) { T page = instantiatePage(driver, pageClassToProxy); initElements(driver, page); return page; } public static void initElements(WebDriver driver, Object page) { final WebDriver driverRef = driver; initElements(new DefaultElementLocatorFactory(driverRef), page); } What is the benefit of having the following line? final WebDriver driverRef = driver; Wouldn't it have made sense to just make the parameter final, and then passing that along to the next method without declaring the new reference?

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