Develop Reference

How do I use a database view as a model in C# MVC

I am using a DATABASE-FIRST approach in C# MVC and all of my generated models are in a sub-folder Models>Generated. One of these models is called SourceSystem which contains the field definitions of the table and the related table entities.
public partial class SourceSystem
{
[Key]
[Column("ID")]
public int Id { get; set; }
[StringLength(100)]
public string SystemName { get; set; } = null!;
[Column("ROWSTAMP")]
public byte[] Rowstamp { get; set; } = null!;
[StringLength(100)]
public string? LinkedServerName { get; set; }
[StringLength(100)]
public string? DatabaseName { get; set; }
[StringLength(20)]
public string? DefaultSourceSchema { get; set; }
[StringLength(20)]
public string? DefaultTargetSchema { get; set; }
[InverseProperty("SourceSystem")]
public virtual ICollection<Domain> Domains { get; } = new List<Domain>();
[InverseProperty("SourceSystem")]
public virtual ICollection<EventProfile> EventProfiles { get; } = new List<EventProfile>();
}
As part of the application there are also a number of synonyms created which will link back to the source databases (based on the Linked Server Name, Database Name and Default Source Schema. This list of synonymns does not live in MY database but are in the msdb database so I have a view that enables me to generate a dataset of the synonyms and associate them back to the SourceSystem table. For note, DelimitedSpit8K takes a string and spits it up, into a record set. Because synonyms use a 2/3/4 part naming convention, I have to reverse them as I need to definately have the last two parts (schema and object name) but the first two (linked server name and database) are optional. Note also that the schema for the view is pow, not the default dbo.
CREATE VIEW pow.Synonymn AS
SELECT
SYN.object_id AS [SystemID]
,SYN.name AS [Synonym]
,SCH.name AS [SourceSchema]
,SYN.base_object_name
,REPLACE(REPLACE(REVERSE(object_name.Item),'[',''),']','') AS [object_name]
,REPLACE(REPLACE(REVERSE(object_schema.Item),'[',''),']','') AS [object_schema]
,REPLACE(REPLACE(REVERSE(object_db.Item),'[',''),']','') AS [object_db]
,REPLACE(REPLACE(REVERSE(object_linked_server.Item),'[',''),']','') AS [object_linked_server]
,SS.ID AS [SourceSystem_Id]
FROM
sys.synonyms AS SYN
JOIN
sys.schemas AS SCH ON SCH.schema_id = SYN.schema_id
JOIN
pow.SourceSystem AS SS ON SS.DefaultTargetSchema = SCH.name
CROSS APPLY
pow.DelimitedSplit8K(REVERSE(SYN.base_object_name), '.') AS [object_name]
CROSS APPLY
pow.DelimitedSplit8K(REVERSE(SYN.base_object_name), '.') AS [object_schema]
CROSS APPLY
pow.DelimitedSplit8K(REVERSE(SYN.base_object_name), '.') AS [object_db]
CROSS APPLY
pow.DelimitedSplit8K(REVERSE(SYN.base_object_name), '.') AS [object_linked_server]
WHERE
object_name.ItemNumber =1
AND
object_schema.ItemNumber = 2
AND
object_db.ItemNumber = 3
AND
(
object_linked_server.ItemNumber IS NULL
OR
object_linked_server.ItemNumber = 4
)
I have manually added a model to my models folder (not Models>Generated):
using Overwatch_API.Models.Generated;
using System;
using System.Collections.Generic;
using System.ComponentModel.DataAnnotations;
using System.ComponentModel.DataAnnotations.Schema;
using System.Text.Json.Serialization;
using Microsoft.EntityFrameworkCore;
namespace Overwatch_API.Models;
//[Table("Synonym", Schema = "pow")]
public partial class Synonym
{
[Key]
[Column("SystemID")]
public int SystemID { get; set; }
[Column("Synonym")]
public string SynonymName { get; set; }
[Column("SourceSystemTargetSchema")]
public string SourceSchema { get; set; } = null!;
[Column("SourceSystemId")]
public int SourceSystem_Id { get; set; }
public string base_object_name { get; set; }
public string object_name { get; set; }
public string object_schema { get; set; }
public string object_db { get; set; }
public string object_linked_server { get; set; }
[ForeignKey("SourceSystemId")]
[InverseProperty("Synonyms")]
//[JsonIgnore]
public virtual SourceSystem SourceSystem { get; set; } = null!;
}
and I have modified the database context:
using Overwatch_API.Models;
...
public virtual DbSet<Synonym> Synonyms { get; set; }
...
modelBuilder.Entity<Synonym>(entity =>
{
entity.ToView(nameof(Synonym))
.HasKey(t => t.SystemID);
});
and I have updated the ViewModel for the SourceSystemVM:
using Overwatch_API.Models;
...
public class SourceSystemVM
{
public int Id { get; set; }
[DisplayName("System Name")]
public string SystemName { get; set; }
[DisplayName("Linked Server")]
public string? LinkedServerName { get; set; }
[DisplayName("Linked Database")]
public string? DatabaseName { get; set; }
[DisplayName("Source Schema")]
public string? DefaultSourceSchema { get; set; }
[DisplayName("Target Schema")]
public string? DefaultTargetSchema { get; set; }
public ICollection<DomainVM> domains { get; set; }
public ICollection<Synonym> synonyms { get; set; }
public SourceSystemVM(SourceSystem ss)
{
Id = ss.Id;
SystemName = ss.SystemName;
LinkedServerName = ss.LinkedServerName;
DatabaseName = ss.DatabaseName;
DefaultSourceSchema = ss.DefaultSourceSchema;
DefaultTargetSchema = ss.DefaultTargetSchema;
domains = new List<DomainVM>();
synonyms = new List<Synonym>();
}
}
When I start the server and run Swagger, and choose the api endpoint
https://localhost:7001/api/SourceSystems
I get the following error message:
InvalidOperationException: The [InverseProperty] attribute on property 'Synonym.SourceSystem' is not valid. The property 'Synonyms' is not a valid navigation on the related type 'SourceSystem'. Ensure that the property exists and is a valid reference or collection navigation.
I am not sure what part of the configuration I have got wrong. I don't want to touch the SourceSytem.cs in the Models>Generated folder as it will get overwritten if the DF models are re-generated. Do I need to create a new partial class in the models folder to extend the generated model, and if so, what would that look like and how do I disambiguate between the Models>SourceSystem.cs and the Models>Generated>SourceSystem.cs when referencing it in the VM and DTOs. Or am I missing an entire concept somewhere?
For context, the Synonym collection is used for view (read) only. The functionality to add a new synonym will have to be managed through a call to a SQL stored procedure, but I need to understand what I have screwed up here first :)
UPDATE
I have added the partial class to the Models folder:
using Overwatch_API.Models;
using Overwatch_API.Models.Generated;
using System.ComponentModel.DataAnnotations.Schema;
namespace Overwatch_API.Models.Generated
{
public partial class SourceSystem
{
[InverseProperty("SourceSystem")]
public virtual ICollection<Synonym> Synonyms { get; } = new List<Synonym>();
}
}
and updated the context:
modelBuilder.Entity<Synonym>(entity =>
{
entity.ToView("Synonym", "pow");
});
and now the API doesn't throw an error message but the synonym array is empty and I'm not sure why: Whether the relationship between the Synonym and SourceSystems is not defined correctly or if the view is not being found/executed to return the details.
UPDATE 2: As per the question from Alex:
I have set up the following in the dbContext:
modelBuilder.Entity<Synonym>(entity =>
{
entity.ToView("Synonym", "pow");
entity.HasOne(d => d.SourceSystem)
.WithMany(p => p.Synonyms)
.HasForeignKey(x => x.SourceSystemId);
});
The Profiler is showing the following queries being run. For the Synonymns API [HttpGet]
SELECT [s].[SystemID], [s].[SourceSchema], [s].[SourceSystem_ID], [s].[Synonym], [s].[base_object_name], [s].[object_db], [s].[object_linked_server], [s].[object_name], [s].[object_schema]
FROM [pow].[Synonym] AS [s]
For the SourceSystem API [HttpGet]
SELECT [s].[ID], [s].[DatabaseName], [s].[DefaultSourceSchema], [s].[DefaultTargetSchema], [s].[LinkedServerName], [s].[ROWSTAMP], [s].[SystemName], [d].[ID], [d].[DomainName], [d].[ROWSTAMP], [d].[SourceSystem_ID]
FROM [pow].[SourceSystem] AS [s]
LEFT JOIN [pow].[Domain] AS [d] ON [s].[ID] = [d].[SourceSystem_ID]
ORDER BY [s].[ID]
Domain is another collection within SourceSystem but it unrelated to the Synonyms. A single join here would create a cartesion collection with both the Domains and Synonymns being repeated. Could this be the problem? The data fetch would either need to do an N+1 query or bring back the cartesian collection and then filter distinct. If so, how do I get around the problem. Is there a way to lazy-load the synonymns in MVC. I could just load them all in the front end (React/Next) and apply a filter in JS to only show the ones connected with the selected SourceSystem but this is spreading the logic about throughout the application stack.

OK. So I worked it out and it is non-trivial so hoping that this helps someone else.
SourceSystems contains multiple ICollections (Domains and Synonyms amongst them) however these create cyclic dependencies so the get uses a SourceSystemViewModel which uses a DomainViewModel which does not contain the cyclic reference back to the SourceSystem. I had to add the Synonyms to the SourceSystemViewModel, but as the Synonyms also contain the cyclic reference I have to create a SynonymViewModel as well.
and then in the SourceSystemsController, when executing the _context.SourceSystems you have to tell it to .Include("ChildCollection") which I had not done.
var ssList = _context.SourceSystems
.Include("Domains")
.Include("Synonyms")
.ToList();
Once this is included you then have to specifically iterate through the ssList, and for each SourceSystemDTO, iterate through both the Domains list and the Synonyms list and map the list items into the relevant arrays.
[HttpGet]
[ResponseType(typeof(List<SourceSystemVM>))]
public async Task<IEnumerable<SourceSystemVM>> GetSourceSystems()
{
List<SourceSystem> ss = _context.SourceSystems.ToList();
IEnumerable<SourceSystemVM> ssDTO = from s in ss select new SourceSystemVM(s);
var ssList = _context.SourceSystems
.Include("Domains")
.Include("Synonyms")
.ToList();
var ssDTOList = new List<SourceSystemVM>();
ssList.ForEach(ss =>
{
var ssDTO = new SourceSystemVM(ss);
foreach (var domain in ss.Domains)
{
var domainDTO = new DomainVM(domain);
ssDTO.domains.Add(domainDTO);
}
foreach (var synonym in ss.Synonyms)
{
var synonymDTO = new SynonymVM(synonym);
ssDTO.synonyms.Add(synonymDTO);
}
ssDTOList.Add(ssDTO);
});
return ssDTOList;
}

Composite indexes with RavenDB

I'm trying to create a composite index using RavenDB. Basically, I have 2 models that I need "joined" and able to perform searches on the result.
Here's an example of my models:
Model 1:
public class UserProfile {
public string ProfileId { get; set }
public string FirstName { get; set }
public string LastName { get; set }
public string EmailAddress { get; set }
}
Model 2:
public class UserProjects {
public string UserProjectId { get; set }
public List<Project> Projects { get; set }
}
Here's the Project Model, in case you're wondering:
public class Project {
public string ProjectId { get; set; }
public string Name { get; set; }
}
The UserProjectId property is as follows: users/<Email Address>/projects.
I was able to create an index that returns all the fields, but I'm not able to search on certain fields.
Here's my index:
public class ProfileProjectIndex : AbstractIndexCreationTask<UserProfile> {
Map = profiles =>
from profile in profiles
select new {
profile.ProfileId,
profile.FirstName,
profile.LastName,
profile.EmailAddress
};
TransformResults = (db, results) =>
from result in results
let project = db.Load<UserProjects>("users/" + profile.EmailAddress + "/projects")
select new {
result.ProfileId,
result.EmailAddress,
result.FirstName,
result.LastName,
project.UserProjectId,
project.Projects
};
}
Now this index, when querying Raven from the web interface, returns the complete list of data I could want, but I need to be able to filter the results based on some values included in the UserProjects.Projects list, for example:
return all user profiles with associated projects when Project.Projects.Contains(x => x.ProjectId == "projects/1234")
Any RavenDB gurus can enlighten me? Oh, and I'm using RavenDB 2.5.

You are probably looking at multi map indexes, see:
http://ravendb.net/docs/article-page/3.0/csharp/indexes/multi-map-indexes

Entity Framework inserting new rows instead of updating them

I have a problem when I am updating data to database. When I want to update data, Entitiy Framework adds new rows to tables that can have multiple rows (tables that have foreign key).
Database model:
When I update Phone/Contact or Tags entity, Entity Framework automatically adds new row instead of updating it
Here is code that I used:
public string UpdateContact(Contact contact)
{
if (contact != null)
{
int id = Convert.ToInt32(contact.id);
Contact Updatecontact = db.Contacts.Where(a => a.id == id).FirstOrDefault();
Updatecontact.firstname = contact.firstname;
Updatecontact.lastname = contact.lastname;
Updatecontact.address = contact.address;
Updatecontact.bookmarked = contact.bookmarked;
Updatecontact.city = contact.city;
Updatecontact.notes = contact.notes;
Updatecontact.Emails1 = contact.Emails1;
Updatecontact.Phones1 = contact.Phones1;
Updatecontact.Tags1 = contact.Tags1;
db.SaveChanges();
return "Contact Updated";
}
else
{
return "Invalid Record";
}
}
EDIT:
Here is EF Model code:
Contact:
public partial class Contact
{
public Contact()
{
this.Emails1 = new HashSet<Email>();
this.Phones1 = new HashSet<Phone>();
this.Tags1 = new HashSet<Tag>();
}
public int id { get; set; }
public string firstname { get; set; }
public string lastname { get; set; }
public string address { get; set; }
public string city { get; set; }
public Nullable<byte> bookmarked { get; set; }
public string notes { get; set; }
public virtual ICollection<Email> Emails1 { get; set; }
public virtual ICollection<Phone> Phones1 { get; set; }
public virtual ICollection<Tag> Tags1 { get; set; }
}
Emails/Tags and Phone have same model (with different name for value)
public partial class Email
{
public int id { get; set; }
public int id_contact { get; set; }
public string email1 { get; set; }
public virtual Contact Contact1 { get; set; }
}

Update properties rather than set new objects.
Updatecontact.Emails1.email1 = contact.Emails1.email1;
Updatecontact.Phones1.number = contact.Phones1.number;
Updatecontact.Tags1.tag1 = contact.Tags1.tag1;
Edit: seems that your contact model has lists of emails, phones and tags. If this is so, then simple assignment won't work. Instead, when sent from the client, you have to find one-by-one and update:
foreach ( var email in contact.Emails1 )
{
// first make sure the object is retrieved from the database
var updateemail = Updatecontact.Emails1.FirstOrDefault( e => e.id == email.id );
// then update its properties
updateemail.email1 = email.email1;
}
// do the same for phones and tags

It's doing that because you're setting the different HashSet values to the values of a completely different collection, namely from what you call contact in that method. In order for you to properly do an update, you're going to have to loop through the emails, phones, and tags to check if those need to be added/updated/deleted on the actual object that you're trying to update.

First, why do you have to search for the contact if you are already receiving it by parameter? That makes me think that you are creating a new one because you are in a different context, if so, then it creates a new record because you have 2 different object in 2 different context.
Try using just one object in the same context to update, EF should mark the object to modification by itself, if not then try making sure before saving that your object has EntityState.Modified.

Recursive Entity Update

I have an entity which holds a list of entities (same as root entity) to represent a Folder structure:
public class SopFolder
{
public int Id { get; set; }
public string Name { get; set; }
public DateTime? LastUpdated { get; set; }
public int Status { get; set; }
public virtual ICollection<SopField> SopFields { get; set; }
public virtual ICollection<SopFolder> SopFolderChildrens { get; set; }
public virtual ICollection<SopBlock> Blocks { get; set; }
public virtual ICollection<SopReview> Reviews { get; set; }
}
This entity is stored in my DB using Code-First Approach which is working fine. I then print the entity to a KendoUI Treeview, let the user modify it and on "save" post it back to the Server to an Action as IEnumerable<TreeViewItemModel> items.
I then look for the ROOT entity with all it's children (there is only one root) and convert it back into an SopFolder object.
To get the full object updated in the database I do the following:
List<SopFolder> sopfolderlist = ConvertTree(items.First());
SopFolder sopfolder = sopfolderlist[0];
if (ModelState.IsValid)
{
SopFolder startFolder = new SopFolder { Id = sopfolder.Id };
//db.SopFolders.Attach(startFolder);
// db.SopFolders.Attach(sopfolder);
startFolder.Name = sopfolder.Name;
startFolder.LastUpdated = sopfolder.LastUpdated;
startFolder.SopFields = sopfolder.SopFields;
startFolder.SopFolderChildrens = sopfolder.SopFolderChildrens;
startFolder.Status = sopfolder.Status;
db.Entry(startFolder).State = EntityState.Modified;
db.SaveChanges();
return Content("true");
}
However this is not working. The model is not updated at all. If I shift the "entityState.Modified" before the modifications, it just creates a complete fresh duplicate of my data in the database (modified of course).
Is my approach correct or do I have to go a different path? What am I missing here? I guess there is another "hidden" id which lets the EF map the entities to the db entries but I am not sure about this. Thanks for help!
UPDATE:
Instead of creatinga new instance of SopFolder I also tried db.SopFolders.Find(sopfolder.Id) and this works for entries with no children. If I have entities with children, it creates a duplicate.
Regards,
Marcus

This is typical Disconnected Graph scenario. Please see this question for possible solutions:
Disconnected Behavior of Entity Framework when Updating Object Graph
You have already figure out the first solution - that is: update entities separately. Actually, what you should do is to fetch the original data from database and then do comparison of what have changed. There are some generic ways of doing that, some of them are described in "Programming EF DbContext" book by J.Lerman, which I strongly recommend to you before doing more coding using EF.
P.S. IMHO this is the worse downside of EF.

Replace SopFolder startFolder = new SopFolder { Id = sopfolder.Id }; with
SopFolder startFolder = db.SopFolders.FirstOrDefault(s=>s.Id.Equals(sopfolder.Id));
// then validate if startFolder != null

I recommend you to create your entity model with ParentId, not children object list. When you need treeview model collect it with recursive function from database.
public class SopFolder
{
public int Id { get; set; }
public string Name { get; set; }
public DateTime? LastUpdated { get; set; }
public int Status { get; set; }
public virtual ICollection<SopField> SopFields { get; set; }
//public virtual ICollection<SopFolder> SopFolderChildrens { get; set; }
public int? ParentFolderId { get; set; }
public virtual ICollection<SopBlock> Blocks { get; set; }
public virtual ICollection<SopReview> Reviews { get; set; }
}
When you create children folders, select it's parent, so collect your data. In childrens case try this :
List<SopFolder> sopfolderlist = ConvertTree(items.First());
SopFolder sopfolder = sopfolderlist[0];
if (ModelState.IsValid)
{
SopFolder startFolder = new SopFolder { Id = sopfolder.Id };
//db.SopFolders.Attach(startFolder);
// db.SopFolders.Attach(sopfolder);
startFolder.Name = sopfolder.Name;
startFolder.LastUpdated = sopfolder.LastUpdated;
startFolder.SopFields = sopfolder.SopFields;
startFolder.SopFolderChildrens = sopfolder.SopFolderChildrens;
foreach (var child in sopfolder.SopFolderChildrens)
{
db.SopFolders.CurrentValues.SetValues(child);
db.SaveChanges();
}
startFolder.Status = sopfolder.Status;
db.Entry(startFolder).State = EntityState.Modified;
db.SaveChanges();
return Content("true");
}

Name table in SQLite-net

I'm building a Windows 8 C#/XAML app that uses SQLite as a storage database, and I'm trying to create multiple tables using the SQLite-net syntax.
From what I've researched so far, a table is created based off of a class. First, I've created an "Account" class via:
public class Account
{
[PrimaryKey, AutoIncrement]
public int ID { get; set; }
public string Name { get; set; }
public string Type { get; set;}
}
And then create a table and enter in initial data later on in the code via:
private static readonly string _dbPath =
Path.Combine(Windows.Storage.ApplicationData.Current.LocalFolder.Path, "data.sqlite");
using (var db = new SQLite.SQLiteConnection(_dbPath))
{
db.CreateTable<Account>();
db.RunInTransaction(() =>
db.Insert(new Account()
{
Name = "MyCheckingAccount",
Type = "Checking",
})
);
}
I want to create multiple account tables, but the db.CreateTable<Account>() syntax just creates a table and the data is inserted into the columns with db.Insert(). I don't see where to enter the name of the table itself.
How do I create multiple tables, i.e. one named "BusinessAccounts" and another "PersonalAccounts" based off of the Account class?
Is there a way to do this with SQLite-net? Or do I need to write out the SQLite command explicitly somehow?

This answer seems to be outdated, in SQLite-net you can now use an attribute on a class to ovverride the table name, for example:
[SQLite.Table("table_customers")]
public class Customer
{
[MaxLength(3)]
public string code { get; set; }
[MaxLength(255)]
public string name { get; set; }
}
So it will create/update that table.

Sqlite-Net uses the class name to create the table, as well as to update the data. To do what you want, you'll need to create separate classes. One way to get around repeating common fields is to use inheritance:
public class Account
{
[PrimaryKey, AutoIncrement]
public int ID { get; set; }
public string Name { get; set; }
public string Type { get; set;}
}
public class BusinessAccounts : Account { }
public class PersonalAccounts : Account { }
To create tables:
db.CreateTable<BusinessAccounts>();
db.CreateTable<PersonalAccounts>();
To insert data:
db.Insert(new BusinessAccounts() {...});
db.Insert(new PersonalAccounts() {...});
Just a note that the above code is untested. You'll want to make sure that the tables are created correctly (e.g. with the proper primary key and autoincrement field).

Just to add that with SQLite-net, you can change the attribute of the class by implementing an initialisation overload and setting the SQLite.TableAttribute like this:
[Table("Account")]
public class Account
{
[PrimaryKey]
[AutoIncrement]
public int ID { get; set; }
public string Name { get; set; }
public string Type { get; set; }
public Account(string name = null)
{
if (!string.IsNullOrEmpty(name))
{
TableAttribute attrname = TypeDescriptor.GetAttributes(this)(0);
attrname.Name = name;
}
}
}
The name defaults to account, but if you initialize the class with a string, it sets the attribute thus you can then create a table with that name.