One of the database view I am trying to import using entity framework contains only two columns, one is an integer type of column and another one is an aggregate function. I am getting the following error.
The table/view does not have a primary key defined and no valid primary key could be inferred. This table/view has been excluded. To use the entity, you will need to review your schema, add the correct keys, and uncomment it.
I understand it is a known scenario and it can be fixed by either including a Key column in the view or modifying the edmx file manually.
I just wanted to know if there is some other solution other than the above two? I do not want to include an additional column in my query and making changes in edmx is not feasible as DB changes are very frequent and the edmx will be overwritten every time I update from db.
You can mark both properties as entity key directly in the designer but you must ensure that the composite value of these two properties will be always unique. If you cannot ensure that you must add another unique column anyway or you may have some other problems when working with such entity set.
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In a netstandard20 project, I'm using Npgsql.EntityFrameworkCore.PostgreSQL 3.1.0 and I'm having an issue using Guid as the type for my primary keys. If I use Database.EnsureCreated() to create the schema, the primary key columns get created with data type uuid. With everything the same except changing it to use Database.Migrate() creates all the primary key columns with data type text and then I get exception: Npgsql.PostgresException : 42883: operator does not exist: text = uuid when I try to perform any operations.
There is a single migration in my project to create the initial database. In that migration and also in the "context model snapshot" that are auto-generated, the primary key columns are all defined as Guid.
I need to both use the Database.Migrate() method to create the database and also have it create the Guid primary key columns as uuid. How can I make sure it creates the columns correctly?
I found this issue and response after posting my question. It led me to the correct answer which was that when I created the migration I was using sqlite. I needed to blow away the migration created against that data provider and regenerate it.
Can anyone explain what's the conceptual difference between #UniqueEntity validator, #UniqueConstraint table annotation and unique=true option of #Column annotation.
I understand that #UniqueConstraint adds UNIQUE index on database level and #UniqueEntity validates on ORM level. So what option shall I use, or do I use all of them?
#UniqueConstraint and unique=true are part of Doctrine and do similar thing.
When you set unique=true on a particular column, then Doctrine will create a unique key on this column physically in database.
#UniqueConstraint can be used to create a unique key in database on multiple columns (complex unique key). But if you pass a single column, then the result will be exactly the same as using unique=true on that field.
#UniqueEntity on the other hand is not a part of Doctrine, but it's a part of Symfony framework. While options above are used by Doctrine to generate proper schema, this one is just a validator used usually by Symfony Form Component at time of submitting the form.
So to answer your final question - yes, you usually should use both #UniqueEntity and one of #UniqueConstraint or unique=true.
As stated in documentation, #UniqueConstraint annotation is used for creation of unique constraint on multiple columns, when unique=true is used for unique constraint on one column.
UniqueEntityValidator exists to show friendly error message and unique database constraint's purpose is to make sure you don't store duplicate data.
So the answer to your question is like this - you should use both database constraint and #UniqueValidator.
I have 2 tables that have a foreign-key relationship through the field that has nchar type.
Database designer successfully created relationship and displays it on database diagram. But entity model created doesn't have this relationship, and as a result dynamic data site doesn't allow automated filtering by that parameter.
Is it possible to force that relationship be mapped to entity data model?
If no, how to apply filter on that field?
Dav Check if your foreign table have primary key or not. I faced same problem but after adding primary key to foreign it got resolved. Please try once.
If still you are facing problem you can use FilterUIHint annotation to do it.
I am unable to understand the line in bold from this msdn page:-
http://msdn.microsoft.com/en-us/library/bb738618.aspx
SaveChanges can generate an UpdateException when an object added to the ObjectContext cannot be successfully created in the data source. This can happen if a row with the foreign key specified by the relationship already exists. When this occurs, you cannot use Refresh to update the added object in the object context. Instead, reload the object with a value of OverwriteChanges for MergeOption.
In a table, a foreign key column can have a single value multiple times. e.g. DepartmentID foreign key in Users Table: More than one User can have same DepartmentID foreign key.
So how can this cause an UpdateException ?
Easy. You have an entity in your context in the Added state with a PK value of something already in the DB. This is common when people try to use stub objects incorrectly. If you want more help than that, you need to isolate your problem and post your code.
I have web application where Iam using linq to business entites i have business data model.
the problem is :
I have table with one column that it dosen't allow null value, when I try to update this table the folloeing error arise:
error The property 'e.g Carrier' is part of the object's key information and cannot be modified
what I can do?
The easiest thing to do is add a second column to the table that has a unique key eg guid and create a read only property on the entity that corresponds to it.
Linq to business entites needs some kind of key to keep track of what to update in the database. Usually this is the primary key on the database table. If you dont have a primary key it cannot reliably update the database and will then send you an exception.
Also if there is no primary key explicitly set on the table linq to business entites will select one of the columns (think its the first column in the table but i could be wrong) to act as a primary key and will therefore not allow you to update it.