I created an Entity Framework model based on an existing database, then generated the POCO entities from the model. The connection string in my web.config isn't Entity Framework, it's just the standard connection string (it's missing the CSDL, SSDL, MSL references).
I can compile my application, but when I run I get this error:
Code generated using the T4 templates for Database First and Model
First development may not work correctly if used in Code First mode.
To continue using Database First or Model First ensure that the Entity
Framework connection string is specified in the config file of
executing application. To use these classes, that were generated from
Database First or Model First, with Code First add any additional
configuration using attributes or the DbModelBuilder API and then
remove the code that throws this exception
My question is, where in my code does it realize the POCOs came from auto generation, and how can I get it to behave like Code First? I don't want to reference the CSDL etc in my connection string.
If the connection string has the metadata, EF thinks it is Model First or Database First. If it is a plain connection string, EF thinks it is Code First. However, if you want to start out doing model first but make EF think you are really doing code first (which is what you are doing), make sure you are using the DbContext code generator, not the default one. Code first POCOs are really that--"plain old c# objects"-- no special database aware or change tracking stuff in them at all. To use the DbContext code generator, right click on your model diagram and choose "Add new code generation item..." then select the ADO.NET DbContext Generator. Also, depending on how you named your primary and foreign keys and/or whether they are more complicated than just simple int IDs, you will probably need to fill in some code to map the relationships between your objects in the "OnModelCreating" method in your context. Delete the line throw new UnintendedCodeFirstException(); and replace it with your mapping code. Otherwise EF may not be able to figure out all the relationships (remember there's no metadata for it to rely on).
Hope this helps.
You need the following in your config file:
<connectionStrings>
<add name="<The name of your class>"
connectionString="metadata=res://*/<test>.csdl|res://*/<test>.ssdl|res://*/<test>.msl;provider=System.Data.SqlClient;provider connection string="data source=<your source>;initial catalog=<your db>;persist security info=True;user id=<your user id>;password=<your password>;multipleactiveresultsets=True;App=EntityFramework""
providerName="System.Data.EntityClient" />
</connectionStrings>
I'm using Database first and resolved this by copying the EDMX generated connection string to the app.config of my startup application. One already existed but apparently they were different
Related
I am using Devart dotConnect for MySQL with Entity Framework 6 in a Windows Forms application (.Net Framework 4.8). I'm using the DB first approach with a dynamic connection string. My application can connect to any number of databases all with the same schema, so I am building the connection string based on input from the user. I have used this approach on several other projects and have never encountered this issue before. I have spent the last day searching for someone reporting a similar issue, with no luck.
I've created my EDMX model using an empty database (meaning no data, but full schema) called entity_model. I can create instances of the DBContext-derived entity class, and I can even use the attached database to perform general queries on the attached server (e.g. get a list of installed database). I can even perform SQL queries into the database identified in the connection string (using DbContext.Database.SQLQuery), and the results are what I expect. However, when I try to use the DbSet-derived members of the Entity class, my queries are always being directed at the database that I used to generate the model, regardless of the database identified in the connection string.
Stepping through the code, I can see that the settings in the entity object all look correct (entity.Database.Connection.ConnectionString looks exactly like I would expect, and entity.Database.Connection.Database has the correct database name). However, if I examine the internal query value (DbSet.SQL) for any of the DbSet objects, I get something similar to this:
SELECT
Extent1.ID,
Extent1.Field1,
Extent1.Field2,
Extent1.Field3,
FROM entity_model.table1 AS Extent1
where entity_model is the database that I used to create the model. I've done enough testing to know that the queries are actually being executed against this incorrect database, rather than the one passed in through the connection string.
As I've said, I've used this same technique on other projects and have not run into this issue. I've even stepped through some old code and I can see that the contents of the DbSet.SQL field contains no reference to any database (neither the one used to create the model, nor the one from the connection string). This is what I would expect to see in my new project as well.
Can someone explain to me how EF decides whether to include the schema name in the DbSet.SQL field? This is making me a little crazy.
I've tried this across a number of the 50 or so databases that I have installed on my machine, so I know the problem is not with any particular database.
I've found a solution (actually 2 solutions) to this problem. The basic problem is that EF is using the schema specified in the edmx EntitySet element by default:
<EntitySet Name="table1" EntityType="Self.table1" Schema="entity_model" store:Type="Tables" />
This behavior can be turned off in 2 ways. Either add the following lines to your applications startup code:
using Devart.Data.MySql.Entity.Configuration;
...
var config = MySqlEntityProviderConfig.Instance;
config.Workarounds.IgnoreSchemaName = true;
Or add the following sections to your config file:
inside the configSections element:
<section name="Devart.Data.MySql.Entity" type="Devart.Data.MySql.Entity.Configuration.MySqlEntityProviderConfigurationSection, Devart.Data.MySql.Entity.EF6, Version=8.21.2066.0, Culture=neutral, PublicKeyToken=09af7300eec23701"/>
And then after the configSections element:
<Devart.Data.MySql.Entity xmlns="http://devart.com/schemas/Devart.Data.MySql.Entity/1.0">
<Workarounds IgnoreSchemaName="true"/>
</Devart.Data.MySql.Entity>
I found a third option online, and that was to simply delete the schema name from each of the EntitySet elements in the edmx file, but I think that could cause some issues if you ever try to update the model from a database.
I'm hopeful that this answer will prove useful to someone else down the road.
In a class library Ado.net Entity Data Model is has generated POCO classes. These were generated fine for the first time. But database changes are not being reflected. In edmx diagram right clicking and choosing Update Model from Database show newly created table but it do not add table even after selecting it to add.
I tried running .tt (by right click and Run custom tool) but even it did not regenerated the Poco classes as per latest DB changes.
Help please
Not a fix but a workaround: Is it not an option to simply remove and regenerate the EDMX and the generated classes? That's what I do, it is much easier than working with the update feature, and the result seems to be the same. Your POCO extensions still remain the same and functional.
I use database first and I have my SQL upgrade scripts, the generated EDMX and my Generated models in source control and the changes there are very easy to manage. Here is a rough outline of my DB upgrade process for each version:
Create .sql script for the upgrade, statements like CREATE TABLE etc.
Delete generated files: Model.Context.tt, Model.tt, Model.edmx
Remove Entities string from Web.config (if you use it)
Create the EDMX and Context files the same way you did for the first time
If you use source control (I hope you do!) check what has changed
Test
Commit!
In my case i needed to save ModelName.edmx, then classes were generated.
Ensure that connections string in app.config is correct. I was using a DataDictionary and my connection string had the following path:
data source=|DataDirectory|*.sqlite
Thus, it wasn't updating. Because this DataDirectory variable was being resolved at runtime.
I'm following the Entity Framework tutorial on:
Link
I've downloaded the source code, and ran. The project works fine (using the default connection string).
<add name="SchoolContext" connectionString="Data Source=|DataDirectory|School.sdf" providerName="System.Data.SqlServerCe.4.0" />
Next i've changed the connection string to connect to a remote server (which successfully connects). However the tables aren't created and when running the application and accessing the controller I get the following error.
Error:
Model compatibility cannot be checked because the database does not contain
model metadata. Model compatibility can only be checked for databases created
using Code First or Code First Migrations.
My database user is 'dbowner' so I wouldn't imagine it's database access issues.
I'm new to EF, and don't know much about Code First Migrations. Have you come across the above error, and would Code Migrations solve this issue? If so why?
From my reading (please correct me if I am wrong) the scenario here is that you have an existing (perhaps empty) database on a remote server that you wish to put your EF code-first work into.
The error is coming about because, I think, EF is looking for a _MigrationHistory table (metadata about what EF code-first migrations have been run against it etc) and can't find it. There is some reasonable coverage of this table here for some background/interest reading.
So to resolve the issue, I think the steps to take are:
Initialise your database so that it acknowledges the EF code-first stuff
Update the database, rolling forward all your migrations to date
I found some good coverage of how to do this here. This blog also has some good coverage of EF topics in general
PS. I am guessing that your .dsf/SQL Compact Edition database wouldn't have had this problem because EF code-first would have created it for you on first run so it was already acknowledged as being a code-first database.
Here is a link to Entity Framework Power Tools. It is made for creating models by 'Reverse Engineering' your Database on a remote server. You can then easily access this database using EF.
Reverse Engineer Code First - Generates POCO classes, derived DbContext and Code First mapping for an existing database
Both of the initializer methods which I had tried fail when the database already exists:
Database.SetInitializer<Context>(new Initializer());
Database.SetInitializer(new DropCreateDatabaseIfModelChanges<Context>());
However it is possible to force the database to be dropped using:
Database.SetInitializer(new DropCreateDatabaseAlways<Context>());
The following SO post provides the answer to my question:
Setting up a Entity Framework Code First Database on SQL Server 2008
I've tried a combination of the two, and have decided that the best solution is to manually go into SQL Management studio and DROP the database, and re-create it using the initializer as this allows me to Seed the contents of the database.
Database.SetInitializer<Context>(new Initializer());
See here for more information on Seeding the database as it is also quite an unstable processess!
How can I get my database to seed using Entity Framework CodeFirst?
Setup - ASP.Net Web Application referencing a separate project which contains the dbml(soon to be edmx) and business logic classes.
I've been using Linq-To-SQL for a few years now and have been using the same setup as is described here for connection string passing from the web.config.
Can the provider connection string of Entity Framework be substituted with a DB connection string already defined in web.config?
So we have added another object context partial class and passed in the connection string using the constructors.
But this has the irritation of forcing me to manually delete the two constructors from the top of the dbml designer class every time it is rebuilt. We are moving to entity framework soon.
Is the same method recommended for EF? And do you still have to manually remove the two constructors on each rebuild?
http://www.connectionstrings.com/
You can find any specific connectionstring you want there. This is dependent on which type of database you are using, I can't explain further because I don't know which one you have.
I am new to EF and i can't work out what I am doing wrong. I have used EF 4.1 "database first" to create a model for an existing database (that i can't change). All of the tables that i need in the database are in a particular schema which for this question i will call "my_schema". In the main properties of the edmx designer file i have set Database Schema Name to "my_schema". When i inspect the raw XML of the edmx file it seems to have the correct schema mappings
e.g.
<EntitySet Name="Events" EntityType="MyModel.Store.Events" store:Type="Tables" Schema="my_schema" />
However the SQL generated when i access the Events entity set on the DbContext class is still:
SELECT ....
FROM dbo.Events
I am not sure if it makes any difference but i am using the ADO.net DBContextGenerator to generate my classes.
Does anybody know what I am doing wrong.
OK i have sussed this now and it boils down to my ignorance of how EF works. I was passing my DbContext an ordinary ADO.net connection string which seems to flip it into code first mode. As such any settings and configuration in my edmx model were ignored and it was looking for attributes on the model classes. As soon as i changed it to use an EF string that includes references to the model metadata files it works. Seems obvious now, no idea how i expected it to magically know about model metadata.