I'm trying to learn EF 6 Code-first in WPF by following some tutorials. Since I'm familiar with model-first I can understand most parts except I've found ContextInitializer a little confusing. I defined a ContextInitializer like this code:
public class ContextInitializer : DropCreateDatabaseIfModelChanges<Context>
{
protected override void Seed(Context context)
{
var customers = new List<Customer>
{
new Customer{Name="Jane",Phone="2238718"},
new Customer{Name="David",Phone="43245608"},
new Customer{Name="Mike",Phone="90814417"}
};
customers.ForEach(cu => context.Customers.Add(cu));
context.SaveChanges();
}
}
and this is my Context class:
public class Context : DbContext
{
public Context()
: base("MVVM")
{
}
public DbSet<Customer> Customers { get; set; }
}
and It created a database at first run which I think it's weird because this class has zero refrences. Since Seed method doesn't fire again, I can't understand how this works.
Can someone explain to me how my ContextInitializer with zero reference created a database?
Does the following section exist in your App.Config?
<contexts>
<context type="(your name space).Context, MVVM">
<databaseInitializer type="(your name space).ContextInitializer, MVVM" />
</context>
</contexts>
If it is, the program knows where to look to find the ContextInitializer. If the database already exists and the tables in the database already match those of the POCO/model classes, nothing happens. If the model has changed or the database doesn’t exist, this class will be invoked, resulting in the database being seeded with your data.
Related
I have an SQLite database, which contains one table named "Main". Each record of this table contains only two fields: ID (integer, primary key) and name (string). There are 100 records in the database.
Using Entity Framework Power Tools I've created the Code First model from the existing database. The model is rather simple:
// MainMap.cs
public class MainMap : EntityTypeConfiguration<Main>
{
public MainMap()
{
// Primary Key
this.HasKey(t => t.ID);
// Properties
this.Property(t => t.name)
.IsRequired()
.HasMaxLength(50);
// Table & Column Mappings
this.ToTable("Main");
this.Property(t => t.ID).HasColumnName("ID");
this.Property(t => t.name).HasColumnName("name");
}
}
// Main.cs
public partial class Main
{
public long ID { get; set; }
public string name { get; set; }
}
// mainContext.cs
public partial class mainContext : DbContext
{
static mainContext()
{
Database.SetInitializer<mainContext>(null);
}
public mainContext()
: base("Name=mainContext")
{
}
public DbSet<Main> Mains { get; set; }
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
modelBuilder.Configurations.Add(new MainMap());
}
}
Now I'm trying to get the records from the database:
mainContext context = new mainContext();
context.Mains.Load();
Now I can use context.Mains.Local with a comfort for different purposes (actually, I bind it to ListView's ItemsSource).
The problem is that context.Main.Load() line executes for about 2.7 seconds. I think, it is too much time as for retrieving about 100 records from a simple database. Although, I'm a newcomer to databases, so, maybe I'm not right and 2.7 seconds is rather suitable period of time. My CPU is Intel i3-3220 (2x3.30 GHz), Entity Framework's version is 6.0.
Maybe, my Code First model is poor, or maybe EF doesn't provide high performance, or maybe there is no need to call Load() method to obtain records (but if I don't call it, context.Mains.Local is empty).
So, how can I increase the performance of getting the records from the database?
Any help and hints will be appreciated.
i ran some tests with both SQLite and SQL Server. on my laptop (corei7 2630QM 2.00GHZ & win7 64bit) the load time for both was ~1.5sec.
then i tried to warm it up with something like
context.Database.Exists();
and the time reduced to ~700ms for both.
i used "Prefer 32-bit" and "Optimize code" options in build tab of the project properties. these options produced best results.
try these and see if the load time changes.
I get this error when I attempt to save to the database.
In the Controller I have the Edit HttpPut
public ActionResult EditSubject(Models.xxxx model)
{
//Database Model Class
SubjectDB subjectdb = new SubjectDB();
// Name of DB Access in Web.config
BeaconDBEntities db = new BeaconDBEntities();
if (ModelState.IsValid)
{
subjectdb.SubjectId = model.SubjectId;
db.SubjectDBs.Add(subjectdb); --> Pops InvalidOperationsException
db.SaveChanges();
}
In Models folder is the model for the database table
SubjectDB.cs
namespace xxx.Models
{
public class SubjectDB
{
public string SubjectId { get; set;}
}
public class BeaconDBEntities: DbContext
{
public DbSet<SubjectDB> SubjectDBs { get; set; }
}
}
Web.config is the connect string for the database
<coneectionStrings>
<add name="BeaconDBEntities" ...............
</connectionStrings>
The first thing I see is that your connection string name 'BeaconDBEntites' does not match your DbContext inherited class name 'BeaconDBEntities' (you are missing an 'i' in the word Entities). Try changing that and see if it fixes it.
When you edit your data then i think you don't need to write code like this when your useing entity framework it's below code
db.SubjecDBs.Add(subjectdb);
db.SaveChanges();
first when you update your data then first your get your data with your id like this it's below
and your create object your entity class. your entity class is your table like below
SubjecDBs objsub=new SubjecDBs();
var data =db.db.SubjecDBs.where(x=>x.SubjectID==ID).ToList();
then you match your data which is you wont to update like below
objsub.SubjecName=data[0].SubjecName
and you match your field which you wont to update then your write below code like this
db.SaveChanges();
i think this will help you...
Howdy, ya'll! First question on StackOverflow! :-)
So here's the scenario: We're working on a web app with Silverlight 4 and using WCF RIA Services 1.0 SP1 Beta for the web service. I have my entities in the Entity Framework Designer, but I'm using a slightly-modified ADO.NET C# POCO Entity Generator template to generate the classes.
What I'd like to do is have a method inside a Domain Service with the following signature:
[EnableClientAccess]
public class ResultService : DomainService
{
[Invoke]
public SerializableResult CalculateResult(EntityOne e1, EntityTwo e2);
}
I am returning both EntityOne and EntityTwo to the client through queries in other services, like so:
[EnableClientAccess]
public class EntityOneService : DomainService
{
public IQueryable<EntityOne> GetEntityOnes();
}
[EnableClientAccess]
public class EntityOneService : DomainService
{
public IQueryable<EntityTwo> GetEntityTwos();
}
Those classes are successfully being generated in the Silverlight project. The SerializableResult does not have a key.
When I try to compile, I get the following error: "Operation named 'CalculateResult' does not conform to the required signature. Parameter types must be an entity or complex type, a collection of complex types, or one of the predefined serializable types."
In my research, the most helpful information I found were in the comments of this post by Jeff Handley.
Of note, Peter asked in a comment:
I get an 'does not conform to the required signature ...' compile error if my complex object has an [Key] Attribute. When I remove this attribute I can use the object as parameter for an Invoke operation.
Jeff's response:
This is by design. Complex objects cannot have Key properties. If you have a Key the class gets treated as an Entity.
So it sounds as if any further efforts to try to get my method to work will be futile. However, I was wondering if anyone else has come across this problem, and what they did to solve it.
Thanks very much!
I have the following and it works for me.
namespace BusinessApplication2.Web
{
using System.ComponentModel.DataAnnotations;
using System.Linq;
using System.ServiceModel.DomainServices.Hosting;
using System.ServiceModel.DomainServices.Server;
[EnableClientAccess()]
public class DomainService1 : DomainService
{
public IQueryable<EntityOne> GetEntityOnes()
{
return null;
}
public IQueryable<EntityTwo> GetEntityTwos()
{
return null;
}
[Invoke]
public SerializableResult GetSerializableResult(EntityOne one, EntityTwo two)
{
return new SerializableResult() { Result = "It woooooorrrked!" };
}
}
public class EntityOne
{
[Key]
public int Id { get; set; }
}
public class EntityTwo
{
[Key]
public int Id { get; set; }
}
public class SerializableResult
{
public string Result { get; set; }
}
}
Many thanks to Mr. Jeff Handley and Mr. Dinesh Kulkarni for the answer (through Twitter).
In order for an Entity to be used as a parameter in an invoke method, that Entity must be exposed through a query method existing within the same DomainService. The intention for this restriction is that
"Each domain service needs to be able to stand on its own."
By adding two dummy Query methods (see Jeff's answer for an example), I was able to compile my code.
What are the requirements for a custom data source to be listed in the 'Data Source' drop-down list when adding a Dataset to a .rdlc report in Report Viewer 2010?
As can been seen from the screen grab, for some reason it is listing potential sources from a variety of referenced assemblies, but I can't see an obvious pattern as to why it is selecting these.
The 'GeneralDataSet' makes sense as that is a strongly-typed Dataset class, but I'm pretty sure most of the others are not, yet the design dialog still lists them.
I'm looking to roll my own custom data source and would prefer it to be selectable from this list.
I think it scans your project file looking for methods that return Lists<> and so on.
So something like:
public class Person
{
public string name { get; set; }
public int age { get; set; }
}
public class GetPeople
{
public List<Person> GetPeopleList()
{
return null;
}
public IEnumerable<Person> GetPeopleIEnumerable()
{
return null;
}
public IQueryable<Person> GetPeopleIQueryable()
{
return null;
}
}
All three show up, so take your pick. (Code is just thrashed out, ignore bad names/practices :))
But when you use a ReportViewer, you will need to manually set the datasets. Selecting it inside the report from what I have found just basically tells it what data to expect. So add an ObjectDataSource or just set it in the code behind.
I noticed the dataset does not appear if the source is exposed as a Property and not a method.
ie this fails to be a selectable data source.
public class FooData
{
public List<string> Data {get;set;}
}
but this will show up as a data source
public class FooData
{
public List<string> GetData();
}
I just had a problem with this also,
my class was returning Lists but would not show up in the datasources list.
I then added a parameterless constructor and it started to show up ( there was not one before ) I assmume this is so the reportviewer can create and instance of it.
eg:
public MyObject()
{
}
I've had a similar problem with custom lists which inherit from List.
You can work around it if your system will allow you to inherit without using interfaces. Ours doesn't.
The project containing this class WILL appear in the DataSource dropdown, and the class itself appears in the DataSet dropdown:
public class AccountList : List<AccountData>
{}
This class will NOT appear as a Dataset, which prevents its project from appearing as a DataSource (notice the "I" in front of AccountData):
public class AccountList : List<IAccountData>
{}
This is a pain because other aspects of our system require the lists to inherit from an interface not a concrete class. I don't know why it doesn't work.
I know this must be an age-old, tired question, but I cant seem to find anything thru my trusty friend (aka Google).
I have a .net 3.5 c# winforms app, that presents a user with a login form on application startup. After a successful login, I want to run off to the DB, pull in some user-specific data and hold them (in properties) in a class called AppCurrentUser.cs, that can thereafer be accessed across all classes in the assembly - the purpose here being that I can fill some properties with a once-off data read, instead of making a call to the DB everytime I need to. In a web app, I would usually use Session variables, and I know that the concept of that does not exist in WinForms.
The class structure resembles the following:
public class AppCurrentUser {
public AppCurrentUser() { }
public Guid UserName { get; set; }
public List<string> Roles { get; set; }
public string Firstname { get; set; }
public string Lastname { get; set; }
}
Now, I have some options that I need some expert advice on:
Being a "dumb" class, I should make the properties non-static, instantiate the class and then set the properties...but then I will only be able to access that instance from within the class that it was created in, right?
Logically, I believe that these properties should be static as I will only be using the class once throughout the application (and not creating new instances of it), and it's property values will be "reset" on application close. (If I create an instance of it, I can dispose of it on application close)
How should I structure my class and how do I access its properties across all classes in my assembly? I really would appreciate your honest and valued advice on this!!
Thanks!
Use the singleton pattern here:
public class AppUser
{
private static _current = null;
public static AppUser Current
{
get { return = _current; }
}
public static void Init()
{
if (_current == null)
{
_current = new AppUser();
// Load everything from the DB.
// Name = Dd.GetName();
}
}
public string Name { get; private set; }
}
// App startup.
AppUser.Init();
// Now any form / class / whatever can simply do:
var name = AppUser.Current.Name;
Now the "static" things are thread-unsafe. I'll leave it as an exercise of the reader to figure out how to properly use the lock() syntax to make it thread-safe. You should also handle the case if the Current property is accessed before the call to Init.
It depends on how you setup your architecture. If you're doing all your business logic code inside the actual form (e.g. coupling it to the UI), then you probably want to pass user information in as a parameter when you make a form, then keep a reference to it from within that form. In other words, you'd be implementing a Singleton pattern.
You could also use Dependency Injection, so that every time you request the user object, the dependency injection framework (like StructureMap) will provide you with the right object. -- you could probably use it like a session variable since you'll be working in a stateful environment.
The correct place to store this type of information is in a custom implementation of IIdentity. Any information that you need to identify a user or his access rights can be stored in that object, which is then associated with the current thread and can be queried from the current thread whenever needed.
This principal is illustrated in Rocky Lhotka's CLSA books, or google winforms custom identity.
I'm not convinced this is the right way but you could do something like this (seems to be what you're asking for anyway):
public class Sessions
{
// Variables
private static string _Username;
// properties
public static string Username
{
get
{
return _Username;
}
set
{
_Username = value;
}
}
}
in case the c# is wrong...i'm a vb.net developer...
then you'd just use Sessions.USername etc etc