Set options values to an entity property - database

I come from Django, and with Django's ORM when defining a model I can set options, for example:
class MyModel(Model):
CHOICES = (...) # List of choices here
# it has tu be a 2-tuple list
# but that's is not the point right now.
choice = IntegerField(choices=CHOICES) # Set the choices.
Now, when MyModel is used to create an instance, the attribute(property) choice can hold only values defined in CHOICES.
There is some like this for EntityFrameworkCore-2.0?
It is something like this possible?
class MyEntity
{
[choices=EnumDefiningChoices]
property enum choices { get; set; }
}

A property can have a single defined value, an int, string, etc in order to be stored in a database.
An approach is to use 2 tables, one for your entity and one for the choices.
MyEntity:
public class MyEntity
{
public int Id { get; set; }
// all the other properties
public int ChoiceId { get; set; } // Here is the refference for the choice
public virtual Choice Choice { get; set; }
}
Choice:
public class Choice
{
public int Id { get; set; }
public string Name { get; set; }
}
As you can see the ChoiceId will allow only values from the Choice table.
However if you want to use an Enum there is no "blocking" mechanism using EF, this must be implemented at the application level.

Indeed, there is a way!
With EF > 6 you can do something like this:
public enum Option
{
option_1 = 1,
option_2,
option_3
}
class SomeEntity
{
public Option Option { get; set; }
}
And you can get the enum option name with:
var option_name = Option.GetName(typeof(Option), some_entity.option_2);
Console.WriteLine(option_name);
References
Working with Enumerated Values in Entity Framework
Enum.GetName Method (Type, Object)

Related

Azure Search - Query

So I'm using the C# nuget wrapper around Azure Search. My problem is I have a index of products:
public class ProductDocument
{
[System.ComponentModel.DataAnnotations.Key]
public string Key { get; set; }
[IsSearchable]
public string Sku { get; set; }
[IsSearchable]
public string Name { get; set; }
[IsSearchable]
public string FullDescription { get; set; }
[IsSearchable]
public List<CustomerSkuDocument> CustomerSkus { get; set; }
}
public class CustomerSkuDocument
{
[IsSearchable]
public int AccountId { get; set; }
[IsSearchable]
public string Sku { get; set; }
}
Example data would be:
new Product() { Key= 100,Name="Nail 101",Sku = "CCCCCCCC", CustomerSkus = new List<ProductCustomerSku>()
{
new ProductCustomerSku() {AccountId = 222, CustomerSku = "BBBB"},
new ProductCustomerSku() {AccountId = 333, CustomerSku = "EEEEEEE"}
}
So the problem is around CustomerSkuDocument.
When I Search I need to pass the AccountId in as well as the search term, however the AccountId is only used for when searching the ProductCustomerSkus.
Basically an Account can have different customer skus but it's only associated to that account - I don't want a separate index per account.
So my call would be something like /AccountId=222&term=BBBB which would find the match.
However /AccountId=333&term=BBBB would not find a match.
So I'm calling it like:
SearchParameters sp = new SearchParameters();
sp.SearchMode = SearchMode.Any;
sp.QueryType = QueryType.Full;
DocumentSearchResult<ProductDocument> results =
productIndexClient.Documents.Search<ProductDocument>(term, sp);
Where term is the normal search term, tried it with adding the AccountId but it doesn't work.
Azure Search does not support repeating data structures nested under a property of the outer document. We're working on this (see https://feedback.azure.com/forums/263029-azure-search/suggestions/6670910-modelling-complex-types-in-indexes), but we still have some work to do before we can release that.
Given that, the example you're showing is not probably indexing the nested parts. Can you post the search index definition you're using? While we work in direct support for complex types, you can see your options for approach here: https://learn.microsoft.com/en-us/azure/search/search-howto-complex-data-types
From the above you'll arribe at a index structure that will also guide your query options. If all you need is equality, perhaps you can simply include the accountId and the SKU in the same field and use a collection field so you can have multiple instances. For your query you would issue a search query that requires the accountId and has the rest as optional keywords.

Entity Framework Code First - One to Many relations from multiple tables

I have a BlobEntity table that contains paths to files for many other tables (tableX, tableY, tableZ, etc...) in my application.
The relation between all the other tables to BlobEntity table is one to many.
Example:
tableX -> BlobTable (OTM)
tableY -> BlobTable (OTM)
tableZ -> BlobTable (OTM)
and the relation is:
public virtual ICollection<BlobEntity> BlobEntity { get; set; }
I'm not sure if this is an issue, but entity framework Code First creates a new FK column in BlobEntity table for each source table.
In my case, BlobEntity contains three FK columns for tableX, tableY and tableZ.
In order to be efficiency, i rather create one column in BlobEntity that contains the FK for the source tables.
Is it reasonable?
Please advise...
Thanks.
No, you can't do this even in plain old SQL.
You can have a foreing key pointing to more than one table; that's why you need
three columns.
If you want to do a "trick" like this, you have to manually manage the relation (I mean, no real FK), but you can't map it into EF.
What about this?
public class EntityA
{
public int Id { get; set; }
public int MyFileID {get;set;}
public virtual MyFiles MyFile { get; set; }
}
public class EntityB
{
public int Id { get; set; }
public int MyFileID {get;set;}
public virtual MyFiles MyFile { get; set; }
}
public class MyFiles
{
public MyFiles()
{
// ReSharper disable once VirtualMemberCallInContructor
FilesForEntityA = new List<EntityA>();
// ReSharper disable once VirtualMemberCallInContructor
FilesForEntityB = new List<EntityB>();
}
public int Id { get; set; }
public int? EntityAId {get;set;}
public int? EntityBId {get;set;}
public virtual ICollection<EntityA> FilesForEntityA { get; set; }
public virtual ICollection<EntityB> FilesForEntityB { get; set; }
}
This way you can have the FK in place and you can easily manager multiple entities.
Obviously if you have many files for each entity, you can go with a N-to-N relationship, like this.

Is it possible to have a relation where the foreign key is also the primary key?

I have a table in a SQL database which should have a relation with one of two tables, but not both.
My manager solved it by using the ID field of the table Competitor as both primary key and as foreign key for the two other tables. None of the tables have autoincremental IDs.
Problem is, when I try to add a new compeitor, it fails unless there is an entry in both of the other tables with the specified ID, which is the opposite of what I want.
Here is an illustration to show you how it's done:
I am sorry if this has been posted or answered before. I could not find anything while searching.
Best Regards
Kajac
The only way to get this right is by subtyping the two Equestrian classes:
public class EquestrianBase
{
public int Id { get; set; }
public virtual Competitor Competitor { get; set; }
}
public class Equestrian : EquestrianBase
{
// Other properties
}
public class TeamEquestrian : EquestrianBase
{
public int TeamLeaderPersonId { get; set; }
// Other properties
}
This could be the competitor class:
public class Competitor
{
public int Id { get; set; }
public virtual EquestrianBase EquestrianBase { get; set; }
// Other properties
}
And the essential configuration:
modelBuilder.Entity<EquestrianBase>()
.HasRequired(e => e.Competitor)
.WithOptional();
Using this model, you'll see that EF adds a Discriminator column to the Equestrian table (of which there is only one now) which discriminates between the two types. Now the database schema enforces that a Competitor have only one Equestrian of either type.
If you want to further fine-tune the inheritance schema, which is called table per hierarchy, look here.
Sure just set the key as Foreign and Primary on the "dependant properties". The Competitor should have the primary key.
public class Competitor
{
[Key]
public int Id { get; set; }
}
public class Equestrain
{
[Key]
[ForeignKey("Competitor")]
public int Id{ get; set; }
public Competitor Competitor { get; set; }
}
public class TeamEquestrain
{
[Key]
[ForeignKey("Competitor")]
public int Id{ get; set; }
public Competitor Competitor { get; set; }
}
MSDN - Configuring a Required to Optional Relationship (One to Zero or One)

Mapping fields in stored procedure to class properties with different names with Dapper

I have this exert from a POCO class with many fields:
public class Call
{
public int Id { get; set; }
public string Customer { get; set; }
public int StatusId { get; set; }
public int UserAssignedToId { get; set; }
public string UserAssignedToName { get; set; }
}
However my stored procedure returns different names to the properties above (in this case the Id is before:
IdCall
IdStatus
IdUserAssignedTo
This is the code I am using to execute the stored procedure:
var call = conn.Query<Call>("CallSPName", new { IdCall = callId }, commandType: CommandType.StoredProcedure).First();
How can I specify a mapping to say I would like "IdStatus" from my stored procedure map to "StatusId" in my POCO class and "IdCall" to "CallId" etc?
I don't have access to change the stored procedures as they are controlled by DBAs and older legacy systems are using them which would break if the fields got changed in the stored procedure.
Any ideas/thoughts appreciated.
The closest thing which comes to my mind is to have private properties mapped to columns returned by the stored procedure and make the public properties with the names you want setting and getting those private fields:
// ...
private int IdStatus;
public int StatusId {
get { return IdStatus; }
set { IdStatus = value; }
}
// ...

Is there an equivalent to "NotMapped" for Dapper.Net and the Dapper.Net extensions?

I've started to play with Dapper.Net, and am really loving it so far - however, I have run into one problem.
Say that I have a POCO class like:
public class Person
{
public string FirstName { get; set; }
public string LastName { get; set; }
public string FullName { get { return FirstName + " " + LastName; } }
}
Now, using Dapper.Net and the Dapper.Net extensions, I want to simply load all instances of that data type from the DB by doing this:
string connectionString = CloudConfigurationManager.GetSetting("DBConnection");
using (SqlConnection cn = new SqlConnection(connectionString))
{
cn.Open();
IEnumerable<Types.Person> entities = cn.GetList<Types.Person>();
var forceMe = entities.ToList();
}
This works fine in the Linq setup, but when it hits the line with the .ToList(), which forces the evaluation, it blows up with "invalid column names" on FullName. Thinking that it might respect the Entity Framework DataAnnotations stuff for NotMapped, I tried adding a NotMapped attribute (after adding EF 5 to the project). This didn't work.
So, the question is, how do I tell Dapper.Net that a column isn't to be expected from the DB? Is this a problem with the extensions, trying to map a DB column for everything it sees in the model POCO? Do I need to revert to writing SQL, and explicitly ask for the columns that I want only, or is there a way to get an equivalent to NotMapped on the column?
I think the only way to to ignore certain properties from being mapped is to implement an auto class mapper, where you can specify your custom field mappings. For example:
public class CustomMapper : ClassMapper<Foo>
{
public CustomMapper()
{
Table("FooTable");
Map(f => f.Id).Column("FooId").Key(KeyType.Identity);
Map(f => f.DateOfBirth).Column("BirthDate");
Map(f => f.FirstName).Column("First");
Map(f => f.LastName).Column("Last");
Map(f => f.FullName).Ignore();
Map(f => f.Calculated).ReadOnly();
}
}
public class Foo
{
public int Id { get; set; }
public DateTime DateOfBirth { get; set; }
public string FirstName { get; set; }
public string LastName { get; set; }
public string FullName
{
get { return string.Format("{0} {1}", FirstName, LastName); }
}
}
In the above example, FullName is being ignored.
The auto-mapper also allows you to adjust table names, in case your POCO class names do not match table names.
Also, keep in mind that you must keep your custom maps in the same assembly as your POCO classes. The library uses reflection to find custom maps and it only scans one assembly.
Hope this helps,
Good luck

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