Is it possible to get SaveChanges to produce an INSERT statement containing only columns that have assigned values for the associated properties.
For example:
administrator.Login = login
administrator.PasswordSalt = salt
administrator.Password = hashed
administrator.CreatedBy = "xxx"
db.Administrators.Add(administrator)
db.SaveChanges()
Should only have four fields in the INSERT statement. Right now, SaveChanges is adding all the fields, setting the unassigned properties to have a value of NULL, which prevents any default value being used. Example: CreatedDate has a default of getdate().
There are at least two different ways to exclude property from INSERT/UPDATE statement in compile-time:
1) EDMX: go to entity and set StoreGeneratedPattern option for a property to Computed or Identity.
If CodeFirst is used: try [DatabaseGenerated(DatabaseGeneratedOption.Computed)] attribite instead.
2) Add AFTER INSERT trigger to SQL table to update an inserted record with default values. How to update inserted field in trigger
I'm not sure it is possible to do in run-time in pure EF.
Related
I have a table in postgres that basically just serves to collect multiple object in a bag. Think like a shopping cart. It only has a uuid that is generated automatically.
How can I insert an empty record into such a table?
INSERT INTO cart() values();
Doesn't work
From the fine INSERT manual:
This section covers parameters that may be used when only inserting new rows. [...]
DEFAULT VALUES
All columns will be filled with their default values, as if DEFAULT were explicitly specified for each column. (An OVERRIDING clause is not permitted in this form.)
[...]
DEFAULT
The corresponding column will be filled with its default value. An identity column will be filled with a new value generated by the associated sequence. For a generated column, specifying this is permitted but merely specifies the normal behavior of computing the column from its generation expression.
So you can use DEFAULT as a value to explicitly use the column's default value:
INSERT INTO cart(your_uuid_column) values(default);
or you can say:
INSERT INTO cart default values;
to use defaults for all the columns.
We are trying to implement a multi tenant architecture in our Web API based application. We are using RLS in SQL Server, and Subscription_Id is, what is given to each subscriber. We have set the default value for Subscription_Id in SQL Server, so while I am calling db.SaveChanges(), I just want to ignore the Subscription_Id going to the SQL Server from the API.
I tried setting the value of Subscription_Id in the SaveChanges() override method but got stuck here.
public override int SaveChanges()
{
var objectType = selectedEntity.CurrentValues.ToObject();
Guid value = new Guid("54E720FC-616B-44C6-8485-5F2185FD7B4C");
PropertyInfo propertyInfo =
objectType.GetType().GetProperty("Subscription_Id");
ChangeTracker.Entries().FirstOrDefault()
.CurrentValues.ToObject().GetType()
.GetProperty("Subscription_Id")
.SetValue(objectType, Convert.ChangeType(value, propertyInfo.PropertyType), null);
return base.SaveChanges();
}
My advice is that you shouldn't modify your SaveChanges() code for this.
A recommended way of using RLS is making the TenantId columns transparent to your EF model and your code, so you don't need to define Tenant ID or navigation properties in your entities. This way you don't need to change your SaveChanges() code, or to explicitly manage and set Subscription_Id values anywhere in your code other that when opening the DB connection.
What you need to do is manually setting a default value constraint in the Subscription_Id columns in your database, with a default value based on the current session Subscription_Id parameter. The value will be set when inserting the records, and implicitly used to filter any subsequent queries and commands at database level.
In case of a new column:
ALTER TABLE SomeEntityTable ADD Subscription_Id nvarchar(128)
DEFAULT CAST(SESSION_CONTEXT(N'UserId') AS nvarchar(128))
In case of an existing column:
ALTER TABLE SomeEntityTable
ADD DEFAULT CAST(SESSION_CONTEXT(N'UserId') AS nvarchar(128)
FOR Subscription_Id
If the column had a previous different DEFAULT value it would be good to also delete its associated obsolete DEFAULT constraint. More info about updating default values in existing columns can be found here.
These columns should not be included in your model. You should not have properties for them in your entity classes. If you are using Database First you should make sure you exclude/ignore these columns when updating your model from your database.
How to do this if you are using EF Code First: you can manually include AlterColumn (or CreateColumn) instructions in a code migration after you generate it with Add-Migration. Do it for every entity table:
public override void Up()
{
AlterColumn("dbo.SomeEntityTable", "Subscription_Id",
c => c.String(
nullable: false,
maxLength: 128,
defaultValueSql: "CAST(SESSION_CONTEXT(N'UserId') AS nvarchar(128))"));
}
(It would be good to add also a Down() method removing the column.)
Warning: Be careful when running this migration if you already have existing records in the tables with an empty Subscription_Id column value (or if you are adding a new Subscription_Id column to a table that already have records). The empty column will be filled with the value of the Subscription_Id in the connection that is executing the migration, which probably will be wrong (you probably don't want all the existing records to be associated to that specific subscription). In that case you may want to include explicit UPDATE instructions with the right Subscription_Id values in your Up() method, with the Sql() method. Something like this:
Sql("UPDATE SomeEntitiesTable SET Subscription_Id= '19bc9b0d-28dd-4510-bd5e-d6b6d445f511' WHERE Id IN (1, 2, 5)");
With Code First you should also remove the Subscription_Id properties from your model classes. If you can't, at least add explicit Ignore() instructions in your configuration code for the Subscription_Id columns, you don't want them in your EF mappings.
Note: I'm assuming here that you created a RLS policy in your DB that uses UserId parameter in SESSION_CONTEXT, and that your application code is setting that value when opening the DB connection, via a DbConnectionInterceptor or something similar.
This page contains more info.
Is there a way to have entity framework use a SQL default value on an insert and yet allow updating to the field. We have an instance where a SQL table has an identity column "id" and another column which is set to ident_current("table"). The only way that I know of to get the field inserted with the default value is to set the field as DatabaseGenerated(DatabaseGeneratedOption.Computed) so that it is ignored on the insert. However by having that attribute then we cannot perform an update to the column. Also it's a self referencing foreign key so we can't do an insert then immediate update to get around the issue. Don't ask me why the table is designed this way - just the way it was set up before so we're kind of stuck with it for now. A simple diagram of our setup is below:
DomainClass:
Class1 {
public int id {get;set;}
[DatabaseGenerated(DatabaseGeneratedOption.Computed)]
public int id2 {get;set;}
public string Name {get;set;}
}
SQL (pseudo):
Table (
id INT which is an identity(1,1) column,
id2 INT NOT NULL with a default value of ident_current("table")
Name nvarchar(50)
)
We would want the insert statement generated by EF to be:
INSERT INTO Table(Name) VALUES('Name')
and the update to be:
UPDATE table
SET id2 = *somenumber*, name = 'Name'
Thanks a lot for all the help. We are using EF 4.3.1.0 if that's needed as well.
There is no way AFAIK. See this and that.
The first link points to a suggestion about using sequences as primary keys, which seems like something you might want to do instead given your example code.
The second link points to a suggestion about generic handling of default values, which is currently not supported either, but would be another potential starting point toward adding support for what you need.
In our database, every table has two DateTime columns, CreatedOn and ModifiedOn, set via triggers in SQL Server. CreatedOn is set on INSERT, and ModifiedOn is set on INSERT and UPDATE.
I am trying to use Entity Framework 4.1. How should I annotate/configure the two properties?
I think it involves the annotation [DatabaseGenerated(DatabaseGeneratedOption.Computed)], but should I use that annotation for both, or should I set [DatabaseGenerated(DatabaseGeneratedOption.Identity)] on the CreatedOn field?
According to MSDN Identity simply implies that The database generates a value when a row is inserted., which seems true here.
Also, should I use [Timestamp]?
Use Identity for CreatedOn and Computed for ModifiedOn. Identity means that value is set only during insert and returned back to application. Computed is set during each modification (including insert) and value is returned back to the application after each executed insert or update.
Just be aware that neither of these properties can be set in the application. Computed columns also can't be part of primary key or foreign key (it will not be your case).
This will only work with existing database. When using code-first Computed can be set only for timestamp or rowversion.
Timestamp is used for optimistic concurrency. If you mark a column as timestamp each update will contain condition WHERE timestampColum = #lastKnownValue. It will update the record only if last known value is the same as current value. If the value is different you will get an exception. It is usually used with timestamp SQL type. Using it with datatime would require some tests. Value of SQL datatime is not the same as value in .NET.
I am sure I am not the first one to struggle with this.
I am using Entity Framework 1 (VS2008) and one of the columns in the table is ModifiedDate. It has DefaultValue in SQL Server (getdate()); so I would like to leave it the DB to do the generation. However, generated SQL has INSERT (... ModifiedDate) VALUES (... null), and the default value doesn't get inserted.
Is it possible to not specify this column at all?
By setting StoreGeneratedPattern in SSDL.