I have an existing EF code first project which has created the database with all nvarchar columns in the database. Now I am starting another project on the same database for statistical purpose. This new project however is using EF core as pointing to same database. When I tried to run the new project, it gives me following error.
"Data type 'VARCHAR' is not supported in this form. Either specify the length explicitly in the type name, for example as 'VARCHAR(16)', or remove the data type and use APIs such as HasMaxLength to allow EF choose the data type."
Now, as I already have production data in the database so I want to make minimum impact to the column types but still wan to use EC core in my new project. I have so many nvarchar columns so setting configuration on individual table is a hard job. Anyone can point me in the right direction?
This seems to be an issue with the 2.0 release of EntityFrameworkCore: https://github.com/aspnet/EntityFrameworkCore/issues/9188
Supposed to get fixed in 2.1 so you may want to wait until then.
Otherwise they suggest manually fixing it like this:
entity.Property(e => e.Comments)
.HasColumnName("Comments")
.HasColumnType("nvarchar(4000)"); // <- Add this
I'm using data annotation and it still works.
[Column(TypeName = "varchar(50)")]
I can confirm its been fixed on later version, not sure about 2.1 but it disappeared in 2.2 for sure.
https://github.com/aspnet/EntityFrameworkCore/issues/13609
Related
Inside of OnModelCreating, I want to be able to ignore a column if the database is on an older migration EF Core 5 throws an exception if I attempt to read from the database directly, or indirectly by querying the applied migrations. I'm not certian that it's even a good idea, since OnModelCreating is used during the migration 😩, but I'll burn that bridge when I cross it.
There are some examples on how one would do this with EF6, but they don't seem to apply anymore with EF Core.
While Ivan Stoev is right that --generally-- you should model the target database without outside input, the real world isn't always that clear-cut. In my particular case, there are multiple service instances (Azure Functions) that need to read and write to a single database. In order to maintain zero downtime, those Functions need to not read or write columns that don't yet exist.
I solved the problem the way Serge suggested. The database has a known version, populated with seed data that increments with every migration. On startup, the service reads that version with a regular old Microsoft.Data.Sql.SqlConnection. This version is then added to the IServiceCollection as a singleton to be used by the DbContext constructor.
When talking to an older database version, OnModelCreating does things like this:
builder.Entity<Widget>(w =>
{
// another option would be to use the migrations table instead of an integer
if (DatabaseVersion < ContextVersions.WidgetNewPropertyAddedVersion)
{
w.Ignore(w => w.NewProperty);
}
else
{
w.Property(w => w.NewProperty)
.HasDefaultValue(0);
}
});
The startup code also detects if it's been started by the Entity Framework tools and does not read the database version, instead assuming "latest". This way, we do not ignore new properties when building the migration.
Figuring out how to let the service instances know that the database has been upgraded and they should restart to get the new database model is an exercise left up to the reader. :)
I have an application already in production using EF 5.0. I'm about to start on the next major revision. But before I do that, I'm trying to clean up a lot of my existing code.
One thing I want to change, is use a different class for one of my table entities. The new class is functionally identical to the previous. The only real difference is the name. E.g. ReceiptEntity will become Receipt.
This is to help simplify things, and stick to a simple naming convention.
However, EF Migrations are wanting to drop-recreate the table. This is not an option because the application is already in production. And I cannot allow for any data-loss.
Is there any way to change the Entity type without recreating the table that would make EF happy?
I was able to fix this by altering the generated migration.
The generated migration tried to create a table(one that already existed), then immediately drop it(which would of resulted in the data-loss).
I deleted all of the generated code, and simply 'Update-Database'ed an empty migration, and this solved the problem for me.
I have to decide about an important item and I need your help.
I'm facing an huge existing database with a lot of default values on nullable columns.
The team has to build a new MVC4 application on top of it (in fact it is a rewrite of old VB6 application).
I (as a consultant) have 'forced' the use of EF5 to get rid of all stored procedures and migrate to a more modern techology.
Now, after my research, it is clear to me that EF5 doesn't support database default values per default. This is why my inserted records are corrupt (they are inserted because the columns are nullable, but with NULL of course).
Some options came up like using the constructor technique, setting the default values in design on the edmx, or playing around with the xml of the edmx.
Despite, these methods are not usefull for us. Where the constructor technique looks ok for me, it is not feasible to do that for all tables in the DB. I also have a 'njet' from the technical person because he wants to maintain these values on 1 place. Same story for setting the default values in design. The database is also not in our scope (read: as less as possible changes to keep existing applications running).
At this point, I'm not sure it EF is the correct choice for our project.
Is somebody aware of (3th party) tools that can fill in the database default values automatically in the generated xml of the edmx file?
Is there som more info about how this xml is build and if there is a possiblity to interfere in the process?
Is there a good readon why these default values should not be taken? Is this going to change in a later release?
Are there other good practices that can be applied to that problem without having all values dupplicated or a massive workload?
Can I arrange something with my poco generator?
I realize there are already a lot of posts of this topic. Too bad, there is no suitable solution for me since we have already something existing and (with all respect) an old VB6 team that I have to convince.
Thanks for your feedback!
As the title says, how do I view the SQL generated by Entity Framework from within my code? I'm running into an error where the EF is crashing because a field is generated by the database (a DateTime field), and I thought I set it to know that the store is generating it via StoreGeneratedPattern, but it's still crashing, so I would like to see what exactly it's trying to push up to the database.
P.S. I've only been using EF for about an hour now... Switching from L2S.
Since you don't have Sql Profiler, your best choice would be LINQPad. You can use your existing assembly.
Click Add connection -> Use a typed data context from your own assembly -> Entity framework and select your dll.
You can write queries directly against your model (or copy-paste from your code). Select the SQL 'tab' under the query window to view the generated SQL code.
You can use the Entity Framework Profiler (EFProf). It's not free, but there's a 30-day trial available. It does a lot more neat stuff besides showing you the SQL statements.
Generally, you should always use SQL Profiler to see the SQL statements that being submitted by EF into your database.
Also, I think you misunderstood about what StoreGeneratedPattern is. If you look at its possible values inside the model, you'll see that it has identity meaning that the value will be generated (by the database) when the row is inserted and will not otherwise change. The other options are Computed, which specifies that the value will be generated on inserts and updates, and None, which is the default.
So EF will not generate that DateTime field on the fly for you, you need to manually create it and then update your model from database so that EF will generate appropriate metadata to work with it at runtime.
The free AnjLab Sql Profiler will work if real SQL Profiler is not available because you're using SQL Server Express: http://anjlab.com/en/projects/opensource/sqlprofiler. It's not quite as nice as the real thing but it gets the job done well enough.
One solution would be to capture the network traffic and have a look at the data on that level. Microsoft Network Monitor does a good job of this.
Of course, that only works if you're using a separate DB server, and the connection is not encrypted.
I have a database that I wish to build an EF model from, however I do not want to include certain columns from the database as the columns concerned are maintained exclusively on the server and should not be manipulated by any application.
Both of the columns are DateTime (if this makes any difference), one of the columns is nullable and is maintained by a trigger on updates and the other is not nullable and set using a default value in the table definition.
I guess I am looking for something like the "Server Generated" option in Linq2Sql; but I cannot find such an option.
Can anybody tell me how to work around this?
Caveat:
I have been trying to introduce business object modelling at my place of work for some years and it has always been rejected because of the amount of additional code that has to be hand-cranked. EF is currently being seen as a viable solution because of the designer and code generation therefore any option that involves hand-cranking the XML will only turn the rest of my colleagues away from EF. I am therefore looking for something that can be done either using the designer or using code.
EDIT:
I guess that what I am looking for here is either...
(a) a way to create the model without EF referencing the columns in the store (ssdl) and therefore not looking to manipulate it in any way
(b) a way to programatically set the "StoreGeneratedPattern" attribute against the property when I create the ObjectContext (the easy answer is to manually manipulate this in the .ssdl, but this would then be overwritten if I refreshed the model from the database and I cannot go down the route where the .csdl, .msl & .ssdl are hand-cranked).
Can you do this with the Entity Framework? Yes; it's easy. Can you do this with the Entity Framework designer? Unfortunately, that is much harder.
The problem you're having is that the column exists in the storage schema (SSDL) in your EDMX. Removing the column with the GUI designer simply removes it from the client schema, not the mapping or the storage schema. However, it's simple enough to go into the EDMX and remove it. Having done that, you can also remove it from the mapping in the client schema portions of the EDMX, and the entity framework will longer complain that it is unmapped.
Problem solved, right?
Well, no. When you use the GUI designer to update the EDMX from the database, the storage schema is thrown away and re-generated. So your column will come back. As far as I know, there is no way to tell the GUI designer to never map a particular column. So you will have to re-do this every time you update with the GUI designer. Fortunately, the EDMX is XML, so you can do this with a XML transform, LINQ, or the XML tool of your choice.
Can you not create a view with the columns you need and import it through entity function wizard and map it to your entities?
You could modify the text template to ignore these columns when generating your entity classes. For example if you added "IGNORE" to the documentation summary, you could modify the template to ignore them by replacing;
Dim simpleProperties as IEnumerable(Of EdmProperty) = typeMapper.GetSimpleProperties(entity)
with;
Dim simpleProperties as IEnumerable(Of EdmProperty) = typeMapper.GetSimpleProperties(entity).Where(Function(p) p.Documentation is nothing orelse p.Documentation.Summary.IndexOf("IGNORE")<0)
Right click on the field in the graphical representation and choose delete. Ive found that sometimes you will get errors when you make a lot of changes to the modeling at once and start to lose track of your changes. Your best bet might be to rebuild the EF generated model.
Keep in mind that when you "update from the database", that old fields on the generated models will not be removed, you will have to remove them manually. For example if you renamed DateField1 to DateField2 in your database, and then you "Update Model from Database", you will now see both DateField1 and DateField2 on the resultant model. This can be a cause of errors.
Do you not want the column to appear in the model at all?
Try selecting the column in the Designer view and hitting the delete key.
Edit
You could make the setter for the property private. Then your app won't be able to modify the value.
Timestamp is a different data type than DateTime. Timestamp seems to be recognized as an attribute the engine manages, much like an identity attribute. You can't "update" a timestamp attribute. Hence, the EDM can manage it correctly (just as it does an identity).
In EDMX designer, select the property and set StoreGeneratedPattern to Computed.