This is first time I am trying EF core. I create separate class library for EF core created dbcontext EXPENSEDBContext class form the existing database and build successfully.
While I tried to select a record through the object of EXPENSEDBContext I could not able to see the Select() and Where()Â as below
var selectvalues = db.Category.Select();
So as an alternate I used foreach instead of Select() as below
using (var db = new EXPENSEDBContext())
{
//
var selectvalues = db.Category;
foreach(var b in selectvalues)
{
Console.WriteLine(b.Name);
}
}
My question is why Select method is not poping up in db.Category.
If you correctly defined Category property as you said in your comment
public virtual DbSet<Catagory> Catagory { get; set; }
so make sure you added the following using statement:
using System.Linq;
If it doesn't compile so make sure to install the System.Linq nuget package:
Install-Package System.Linq
Related
I am doing a online ASP.net MVC5 course from udemy.I added a new column to my Table using EF migration.
Name Column Added
namespace Vidly.Migrations
{
using System;
using System.Data.Entity.Migrations;
public partial class AddNameToMembershipTypes : DbMigration
{
public override void Up()
{
AddColumn("dbo.MembershipTypes","Name",c => c.String(nullable:false));
}
public override void Down()
{
DropColumn("dbo.MembershipTypes","Name");
}
}
}
Then I updated my database for this migration.
Screen Shot for Confirmation
Customer and MembershipTypes Tables have one-to-one relationship and I am able to retrieve MembershipTypes fields from the Customer Table.
The only problem is that The new column "Name" I just added to the MembershipTypes as I described at the very top is NOT getting retrieved from the View.
Following is The Visual confirmation(Although I tried to add Name but got error)
When I forcefully tried to access Name I got following
I am Not getting why I am Not being able to access Name Field as I have added some values too using migration and updated my database.
My feeling is that the link between Customer and MembershipTypes needs to be updated somehow but I donot know how?
The changes you have in your AddNameToMembershipTypes is only for updating your database schema. That will not automatically update your entity class. You still need to add the new property to your MemberShipType class.
public class MembershipType
{
public string Name { set;get;} // This one here
// Your existing properties here
public int DurationInMonths { set;get; }
}
Is it possible to call a TVF in EF6 Code First?
I started a new project using EF6 Database first and EF was able to import a TVF into the model and call it just fine.
But updating the model became very time consuming and problematic with the large read-only db with no RI that I'm stuck dealing with.
So I tried to convert to EF6 code first using the Power Tools Reverse Engineering tool to generate a context and model classes.
Unfortunately the Reverse Engineering tool didn't import the TVFs.
Next I tried to copy the DBFunctions from my old Database First DbContext to the new Code First DbContext, but that gave me an error that my TVF:
"cannot be resolved into a valid type or function".
Is it possible to create a code first Fluent mapping for TVFs?
If not, is there a work-around?
I guess I could use SPs instead of TVFs, but was hoping I could use mostly TVFs to deal with the problematic DB I'm stuck with.
Thanks for any work-around ideas
This is now possible. I created a custom model convention which allows using store functions in CodeFirst in EF6.1. The convention is available on NuGet http://www.nuget.org/packages/EntityFramework.CodeFirstStoreFunctions. Here is the link to the blogpost containing all the details: http://blog.3d-logic.com/2014/04/09/support-for-store-functions-tvfs-and-stored-procs-in-entity-framework-6-1/
[Tested]
using:
Install-Package EntityFramework.CodeFirstStoreFunctions
Declare a class for output result:
public class MyCustomObject
{
[Key]
public int Id { get; set; }
public int Rank { get; set; }
}
Create a method in your DbContext class
[DbFunction("MyContextType", "SearchSomething")]
public virtual IQueryable<MyCustomObject> SearchSomething(string keywords)
{
var keywordsParam = new ObjectParameter("keywords", typeof(string))
{
Value = keywords
};
return (this as IObjectContextAdapter).ObjectContext
.CreateQuery<MyCustomObject>(
"MyContextType.SearchSomething(#keywords)", keywordsParam);
}
Add
public DbSet<MyCustomObject> SearchResults { get; set; }
to your DbContext class
Add in the overriden OnModelCreating method:
modelBuilder.Conventions.Add(new FunctionsConvention<MyContextType>("dbo"));
And now you can call/join with
a table values function like this:
CREATE FUNCTION SearchSomething
(
#keywords nvarchar(4000)
)
RETURNS TABLE
AS
RETURN
(SELECT KEY_TBL.RANK AS Rank, Id
FROM MyTable
LEFT JOIN freetexttable(MyTable , ([MyColumn1],[MyColumn2]), #keywords) AS KEY_TBL
ON MyTable.Id = KEY_TBL.[KEY]
WHERE KEY_TBL.RANK > 0
)
GO
I was able to access TVF with the code below. This works in EF6. The model property names have to match the database column names.
List<MyModel> data =
db.Database.SqlQuery<MyModel>(
"select * from dbo.my_function(#p1, #p2, #p3)",
new SqlParameter("#p1", new System.DateTime(2015,1,1)),
new SqlParameter("#p2", new System.DateTime(2015, 8, 1)),
new SqlParameter("#p3", 12))
.ToList();
I actually started looking into it in EF6.1 and have something that is working on nightly builds. Check this and this out.
I have developed a library for this functionality. You can review my article on
UserTableFunctionCodeFirst.
You can use your function without writing SQL query.
Update
First of all you have to add reference to the above mentioned library and then you have to create parameter class for your function. This class can contain any number and type of parameter
public class TestFunctionParams
{
[CodeFunctionAttributes.FunctionOrder(1)]
[CodeFunctionAttributes.Name("id")]
[CodeFunctionAttributes.ParameterType(System.Data.SqlDbType.Int)]
public int Id { get; set; }
}
Now you have to add following property in your DbContext to call function and map to the property.
[CodeFunctionAttributes.Schema("dbo")] // This is optional as it is set as dbo as default if not provided.
[CodeFunctionAttributes.Name("ufn_MyFunction")] // Name of function in database.
[CodeFunctionAttributes.ReturnTypes(typeof(Customer))]
public TableValueFunction<TestFunctionParams> CustomerFunction { get; set; }
Then you can call your function as below.
using (var db = new DataContext())
{
var funcParams = new TestFunctionParams() { Id = 1 };
var entity = db.CustomerFunction.ExecuteFunction(funcParams).ToList<Customer>();
}
This will call your user defined function and map to the entity.
I just set about updating a project from Entity Framework 4.3.1 and .NET 4 to Entity Framework 5.0 and .NET 4.5. I updated the .NET version first, and ensured that I'm referencing EF 5.0.0.0 rather than the .NET 4 compatible 4.4.0.0.
I have a class structure like
public class MyBase
{
[NotMapped]
public bool MyProperty { get; set; }
}
public class MyDefinition : MyBase
{
// Some other properties
}
When I attempt to load some MyDefinition instances
using (MyContext ctx = new MyContext())
{
ctx.Configuration.AutoDetectChangesEnabled = false;
ctx.Configuration.LazyLoadingEnabled = false;
ctx.Configuration.ProxyCreationEnabled = false;
var defs = from def in ctx.MyDefinitions.AsNoTracking() select def;
foreach (MyDefinition def in defs) // <-- Exception here
{
// Do stuff
}
}
I get a SqlException
Invalid column name 'MyProperty'.
It is as if NotMapped is respected for purposes of determining whether the existing schema is valid, but the SELECT generated by EF 5 expects there to be a MyProperty column.
The base class and derived class are defined in different assemblies. Both assemblies were carefully checked to ensure they reference EF 5.0.0.0 and target .NET 4.5.
Intellisense claims that NotMapped is System.ComponentModel.DataAnnotations.Schema.NotMapped
How can I prevent EF 5 from selecting that non-existent column?
Add this
using System.ComponentModel.DataAnnotations.Schema
D'oh!
I also updated to VS 2012 today. Something unrelated broke with a post-build event, which caused an earlier version of the assembly containing the base class to be available to the derived class. Fixing the post build event resolved the issue.
I am trying to use mvc-mini-profiler for db-first EF, but it is not working properly.
(note that I'm using objectcontext, not dbcontext)
Here is the list of stackoverflows I've tried:
Setup of mvc-mini-profiler for EF-db- first
How to get MVC-mini-profiler working on EF 4.1 Database First
versions:
Entity Framework: 4.3.1
MiniProfiler: 2.0.2
MiniProfiler.ef: 2.0.3
This is how I setup miniprofiler:
I've added the following stuff in Global.asax
protected void Application_BeginRequest(
{
MiniProfiler.Start();
}
protected void Application_EndRequest()
{
MiniProfiler.Stop();
}
protected void Application_Start()
{
...
MiniProfilerEF.Initialize_EF42();
}
Then configure an objectcontext,
var entityConnection = new EntityConnection(ConnectionString);
var profiledDbConnection = new EFProfiledDbConnection(entityConnection, MiniProfiler.Current);
var context = profiledDbConnection.CreateObjectContext<MyContext>();
var list = context.MyEntities.ToList();
If I execute this, the following exception occurs when running "context.MyEntities.ToList()"
[System.Data.EntityCommandCompliationException]
the message in the inner exception says:
EntityClient cannot be used to create a command definition from a store command tree.
Have I configured wrong? Any help?
thanks,
I use MiniProfiler and database first Entity Framework and it does work well. You may need to turn off the database initialization strategy inside of your database context as per this related answer: https://stackoverflow.com/a/9762989/325727
public class EmployeeContext : DbContext
{
static EmployeeContext() { Database.SetInitializer<EmployeeContext>(null); }
public IDbSet<Employee> Employees { get; set; }
}
The parameter null turns off database initialization by making sure that there is no initializer available.
Error: The ObjectContext instance has been disposed and can no longer be used for operations that require a connection.
I am trying to create a WCF service with Entity Framework (VS 2010, .NET 4). When I run it, I get the above error.
I read something about editing the T4 template, but it appears that it already has
[DataContractAttribute(IsReference=true)]
public partial class Person : EntityObject
and
[DataMemberAttribute()]
public global::System.Int32 ID
{
get
{
return _ID;
}
I am not sure what the difference is between
[DataMemberAttribute()] and [DataMember]
or
[DataContractAttribute(IsReference=true)] and [DataContract]
either.
public Person GetPersonByID(int id)
{
using (var ctx = new MyEntities())
{
return (from p in ctx.Person
where p.ID == id
select p).FirstOrDefault();
}
}
How does WCF and EF work together, properly?
Do you have navigation properties in your Person class? Did you disable lazy loading? Otherwise it will probably try to load content for navigation properties during serialization and it fails because of closed context.
To your other questions:
[DataMemberAttribute()] and [DataMember] are same. It is just shorter name.
[DataContractAttribute(IsReference=true)] and [DataContract] are not same. IsRefrence allows tracking circular references in navigation properties. Without this parameter circular reference causes never ending recursion.