Mapping Database Views to EF 5.0 Code First w/Migrations
Solution 1
You have specified that the ClientStatisticsView
entity should be mapped to a table named "ClientStatistics". So entity framework will generate a migration containing an instruction to create that table. But you have independently created that view in the database so to prevent the error you are getting you should remove the CreateTable
instruction from the Up
migration.
I think a better way to do it is to create the view in the migration by running sql like this:
public override void Up()
{
Sql("EXEC ('CREATE View [dbo].[ClientStatistics] AS --etc"
}
public override void Down()
{
Sql(@"IF EXISTS (SELECT
*
FROM sys.views
WHERE object_id = OBJECT_ID(N'dbo.ClientStatistics'))
DROP VIEW dbo.ClientStatistics)")
}
That way your views and tables are specified in one place and you can safely migrate up and down
Reference
http://elegantcode.com/2012/04/12/entity-framework-migrations-tips/
Solution 2
I'm actually working with Entity Framework "Code First" and views, the way I do it is like this:
1) Create a class
[Table("view_name_on_database")]
public class ViewClassName {
// View columns mapping
public int Id {get; set;}
public string Name {get; set;}
// And a few more...
}
2) Add the class to the context
public class ContextName : DbContext {
// Tables
public DbSet<SomeTableClassHere> ATable { get; set; }
// And other tables...
// Views
public DbSet<ViewClassName> ViewContextName { get; set; }
// This lines help me during "update-database" command
protected override void OnModelCreating(DbModelBuilder modelBuilder) {
// Remove comments before "update-database" command and
// comment this line again after "update-database", otherwise
// you will not be able to query the view from the context.
// Ignore the creation of a table named "view_name_on_database"
modelBuilder.Ignore<ViewClassName>();
}
}
A little bit late but I hope this helps somebody.
If there was a way to ignore the creation of a table named as the view during "update-database" and not-ignore after this that would be great.
Corey Adler
Software developer with over 11 years of experience. Versatile programmer who has worked on diverse projects ranging from enterprise SaaS software to corporate websites. Experienced in leading teams of developers to deliver quality products to customers. Ability to code for both Web and Windows applications in either a front-end or back-end capacity. Hard working and reliable engineer who will go beyond his job description to help the company attain greater heights.
Updated on July 18, 2022Comments
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Corey Adler almost 2 years
I'm trying to map a SQL View to an entity in EF 5.0 Code First w/Migrations for displaying some basic information on a page without having to query multiple tables for that information (which currently takes ~20 seconds to load. NOT GOOD.). I've heard that it is possible to do, but I haven't been able to figure out or find online a way to properly do so.
EDIT: For a more in-depth look at my solution to this problem, read this blog post on the subject.
Here is my View:
CREATE VIEW [dbo].[ClientStatistics] AS SELECT ROW_NUMBER() OVER (Order By c.ID) as Row, c.LegacyID, c.ID, c.ClientName, slc.AccountManager, slc.Network, (SELECT MAX(CreatedDate) AS Expr1 FROM dbo.DataPeriods WHERE (ClientID = c.ID)) AS LastDataReceived, (SELECT MAX(ApprovedDate) AS Expr1 FROM dbo.DataPeriods AS DataPeriods_2 WHERE (ClientID = c.ID)) AS LastApproved, (SELECT MAX(ReportProcessedDate) AS Expr1 FROM dbo.DataPeriods AS DataPeriods_1 WHERE (ClientID = c.ID)) AS LastReportProcesssed FROM dbo.Clients AS c INNER JOIN dbo.SLClients AS slc ON c.ID = slc.ClientID
Here is the entity:
public class ClientStatisticsView { [Key] public int Row { get; set; } public int LegacyID { get; set; } public int ClientID { get; set; } public string ClientName { get; set; } public string AccountManager { get; set; } public string Network { get; set; } public DateTime LastDataReceived { get; set; } public DateTime LastApproved { get; set; } public DateTime LastReportProcessed { get; set; } }
And finally my mapping in
DbContext
:protected override void OnModelCreating(DbModelBuilder modelBuilder) { modelBuilder.Conventions.Remove<OneToManyCascadeDeleteConvention>(); modelBuilder.Entity<ClientStatisticsView>().ToTable("ClientStatistics"); base.OnModelCreating(modelBuilder); }
All of this gives me the following error:
There is already an object named 'ClientStatistics' in the database.
What am I doing wrong? Is there any way to me to accomplish this, or should I be doing something else instead?
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Corey Adler over 10 yearsI just want to add, for anyone seeing this answer, that you will need to use the
add-migration
command at the beginning in order for it to map properly. -
spender almost 7 yearsIf you're fastidious about making all schema changes via migrations, then the
IF EXISTS
clause of theDown
method is not required. -
Jonathan Stark almost 7 years@spender that is true. I use the default scripting from Sql Server, which puts in the
IF EXISTS
clause automatically. I don't feel the need to remove it -
Vincent almost 7 yearsThat's the only I found to resolve the migration with views issue, there is another missing bit in your code. When you remove comments/comment the ignore line, EF will throw the exception, I add the following line before the ignore to get it working finally. Database.SetInitializer<RegulatoryPortalDataContext>(null);