I am using EF code first approach. I need to rename my PK column name.
public class classname
{
[Key]
public int OldId { get; set; }
}
I need to change OldId to NewId. I tried renaming my OldId to NewId, I tried updating my database with Migration but that didn't help.
I tried renaming both in column name and model and again when I tried to update my database I still get error.
How can I rename my primary Key column without losing its data?
Is the question that OldId is not used in your code anymore but is still in your database, or is your problem that it OldId is in your code but has a different column name in your database?
You can use fluent API or data annotations if you want to tell entity framework that the name of property in your DbSet has a different column name in the database:
Fluent API Method
public class MyDbContext : DbContext
{
public DbSet<ClassName> ClassNames {get; set;}
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
// Tell entity framework that you are now building ClassName:
var classNameConfig = modelBuilder.Entity<ClassName>();
// ClassName has an int primary key in OldId:
classNameConfig.HasKey(className => className.OldId);
// "columnX" in the database corresponds with property OldId
classNameConfig.Property(className => className.OldId)
.HasColumnName("columnX");
}
}
Of course in this specific example this can be concatenated into one statement.
The nice thing about fluent API is that you disconnect your classes from the actual database representation. This hides how the actual database names its columns, column order, min size, max size etc from the user of the DbSets.
Just specify a different DbContext, and you can use the same classes with a different Db.
For instance, if you want to use the same entity framework classes in different databases:
class BaseContext : DbContext
{
public DbSet<MyClass> MyClasses {get; set;}
}
// context to be used with database X:
class DataBaseXContext : BaseContext
{
protected override void OnModelCreating(
DbModelBuilder modelBuilder)
{
// I want to use "columnX" for property A, which is optional:
modelBuilder.Entity<MyClass>
.Property(p => p.A)
.HasColumnName("columnX")
.IsOptional();
}
}
// context to be used with database Y:
class DataBaseXContext : BaseContext
{
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
// I want to use "columnY" for property A, which is required:
modelBuilder.Entity<MyClass>
.Property(p => p.A)
.HasColumnName("columnY")
.IsRequired();
}
}
Data Annotations Method
If you are absolutely sure you want your classes to be used in only one database, with one pre-defined model, you could use Data Annotations.
However, your question shows that it is not uncommon that the same classes will be used in a different database model. So, although this method is very commonly used, I urge you to reconsider a decision to use Data Annotations.
public class classname
{
[Key]
[Column("ColumnX")]
public int OldId { get; set; }
}
changing the Identity column may lead to instability and you cant change anything with the column unless you kill all the Key constraints (all table relation ship)
t will be tooo complicated i would advice you that if data isnt Important then just delete the database and re run migraions it will recreate the database again
The name of the entity property can be different from the name of the database column.
If you need to change the name of the column on the database you can do it with the DBMS manager (SQL Server Enterprise Manager if you are using SQL Server) or running the proper DDL statement (sp_rename on SQL Server) then set the new column name on the property using the attribute ColumnAttribute
[Column("NewId")]
[Key]
public int OldId { get; set; }
If you need to change the name in the code but not on the database you can do a similar thing
[Column("OldId")]
[Key]
public int NewId { get; set; }
In this case you should do a refactor (rename with F2 if you have standard visual studio Keys or Ctrl+R, R if you are using resharper)
If you need to change both you can do both.
Related
I'm working on an ASP.NET MVC project, I use Entity Framework (Database First), I created a data model depend on SQL server database, I created a Table in the database and I updated the data model from the database, and when I try to add a record to the new table I created (this table doesn't have a PK) I got an error, when I search about the error I Understood that in Entity Framework need to have a PK for Entity.
So I ASK if I can set a Primary Key for an Entity without affect database, or any other solution to solve this problem.
You can use partial Class for set Key and without effect Original Model and Database
// orginal class **Entity** `YourEntity.cs`
public class YourEntity
{
public int Id { get; set; }
}
Then create a new Class must name different ordinal class ex YourEntityMeta.cs it is physical name
// must change name ordinal class `YourEntity.cs` but add **partial** keyword
[MetadataType(typeof(Metadata))]
public partial class YourEntity
{
sealed class Metadata
{
[Key]
public int Id { get; set; }
}
}
Entity Framework always needs a primary key column with name id. Add a column (id) in the database table and set "Is Identity: true" for it. Then update the database model of your project.
I'm using Entity Framework to map some tables, but I can't do this unless I declare some column as the primary key.
The problem here is that my table in my database don't have a primary key and has millions of rows. I don't have permission to create a new Id column.
[Table("MYTABLE")]
public class myTable
{
[Column("NUMX")]
public virtual string NumX { get; set; }
[Column("NAME")]
public virtual string Name { get; set; }
[Column("AGE")]
public virtual int AGE { get; set; }
}
Obs: If I add the [Key] attribute to some column like Age, it works, but returns the wrong data.
Is there some way to omit the primary key?
I Figured out the problem.
Composite Keys works for me:
eg:
In my Context I defined some keys, not only one, but three keys:
public class MyContext : DbContext
{
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
**//Here is the secret**
modelBuilder.Entity<MyModel>().HasKey(x => new { x.NumX, x.Name,x.Age});
}
}
Entity Framework requires a primary key unlike SQL.
EF use the primary key to uniquely identify rows (for example when you use .Find() or to perform update operations).
Infact not having a primary key remember a SQL VIEW, where you can only read data.
If any of the columns uniquely identify a certain row set it as a primary key (it can't be NULL) also if in Sql it isn't a key.
Otherwise if the combination of the columns are uniquely, create a composite key with these columns.
Remember that you should have a primary key in the 99% of cases, when you don't have a primary key you should stop and think if it make sense.
I am having .NET MVC 5 and Identity...
I am trying to get a one to one relationship for my Member class to my MemberInfo class..
So, My classes looks something like this:
IdentityUser is in the Microsoft.AspNet.Identity.EntityFramework namespace with string Id as its ID.
public class GRNUser : IdentityUser {
....
....
}
public class MemberUser : GRNUser {
public virtual Member MemberInfo {get; set; }
}
public class Member {
public int ID {get; set; }
public string MemberUserID {get; set; }
public virtual MemberUser MemberUser { get; set; }
}
In my Context, I have this
modelBuilder.Entity<Member>().HasRequired(m => m.MemberUser)
.WithOptional(u => u.MemberInfo);
So, the MemberUser and Member should be able to navigate to and from each other using the MemberUser's ID property and Member's MemberUserID property.
However, when my Database is created, it has an additional column "MemberUser_Id" instead of using my MemberUserID that I specified. How do I make it use "MemberUserID" that I specified?
I've tried using a few combination so of the ForiegnKey Data Annotation, but keeps on getting this error:
Member_MemberUser_Source: : Multiplicity is not valid in Role 'Member_MemberUser_Source' in relationship 'Member_MemberUser'. Because the Dependent Role properties are not the key properties, the upper bound of the multiplicity of the Dependent Role must be '*'.
I don't know whether i understood you right or not, but i'l do my best to help.
(I'l assume that you work with code first migration)
If you want to make a one-to-one relation, why not try to make a standalone entity for your info which will have a foreign key for the user entity and that foreign key will be annotated as the primary key of the entity?
Another way is why just not add whatever attributes you like to the Application User entity and work with it?
In any case i might have misunderstood your purpose, so please feel free to explain further since your post is a bit confusing.
I want to generate a model based on an existing database -- I thought it would be as simple as writing the model, adding a DbContext class, and configuring a connection string:
namespace MyProject.Models
{
public class Account
{
public int Id { get; set; }
public string Email { get; set; }
public string Name { get; set; }
}
public class AccountDBContext : DbContext
{
public DbSet<Account> Accounts { get; set; }
}
}
With a simple boilerplate controller
public ActionResult Index()
{
return View(db.Accounts.ToList());
}
The boilerplate view, which I won't post here, which lists all of the members of the db object that we return.
ANd finally, a connection string:
<add name="AccountDBContext" providerName="System.Data.SqlClient" connectionString="[server connection string]" />
Only problem is I don't see any entries being displayed. It's definitely connecting, but not retrieving or displaying the data that the particular DB contains.. am I missing something?
Edit
Ok, so first thing is first: it wasn't connecting. I had a typo in my connection string name. It was hitting the default, and subsequently displaying nothing.
What I am getting now, though, is The model backing the 'AccountDBContext' context has changed since the database was created.
Is this because my model doesn't match exactly to what the database contains?
This is the "Code First with an Existing Database" scenario.
What version of EF are you using?
In EF 4.3 when you let code first create a database for you, it inserts a Migration-History table into the new database. It’s hidden in System Tables.This is equivalent to the EdmMetadata table you got with EF 4.1 & 4.2. But when you already have the database you can use code first migrations. (http://msdn.microsoft.com/en-US/data/jj591621)
Either way you should probably check if such a table exist. If it does you can delete it and then you'll be solely responsible to correctly matching your pocos to the database.
Another quick workaround i have found is putting
Database.SetInitializer<YourContext>(null);
to your Application_Start() in Global.asax
See also this similar question: Entity Framework Code Only error: the model backing the context has changed since the database was created
I have a set of classes as my domain objects.
I have a set of configuration files to map these objects (EntityTypeConfiguration<>).
When I add a property to any of the domain objects without mapping to a column, the dbcontext attempts to query for the column, ignoring the fact that it is not mapped.
I must be missing a setting either in the configuration code or the dbcontext code. I do not want to add an attribute to the poco class (decorating the pocos tie them to a specific persistence implementation, which I wish to avoid).
On the call against the IQueryable to populate a ticket object, the call fails with the message:
Invalid column name 'NotInDatabase'.
public class Ticket
{
public Ticket()
{
}
public virtual int Id
{
get;
set;
}
public virtual string Title
{
get;
set;
}
public virtual string Description
{
get;
set;
}
public string NotInDatabase
{
get;
set;
}
}
internal class TicketConfiguration : EntityTypeConfiguration<Ticket>
{
public TicketConfiguration()
{
ToTable("ticket_table_name");
HasKey(o => o.Id)
.Property(o => o.Id)
.HasColumnName("ticketId")
.HasDatabaseGeneratedOption(DatabaseGeneratedOption.Identity)
.IsRequired();
Property(o => o.Title).HasColumnName("TicketTitle");
Property(o => o.Description).HasColumnName("TicketDescription");
}
}
Note:
Please do not suggest using "Database First" or "Model First" for my situation. I want to map poco objects to the database using the features of code first, even though I have an existing db structure. I am comparing this to nhibernate and really want to stick to a similar structure (since Microsoft "adopted" fluent nhibernate's approach, it's pretty easy to compare apples to apples).
Thanks!
.Ignore should do the trick or by attribute it's called [NotMapped]