How To Insert Data In FluentAPI Mapping Table - entity-framework

Question

I have a A Table, B Table and AB (Mapping Table)
A
public class A
{
public int AID{ get; set; }
[JsonIgnore]
public virtual ICollection<B> Bs { get; set; }
}
B
public class B
{
public int BID { get; set; }
[JsonIgnore]
public virtual ICollection<A> As { get; set; }
}
ApplicationDbContext
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
base.OnModelCreating(modelBuilder);
modelBuilder.Entity<B>()
.HasMany(s => s.As)
.WithMany(c => c.Bs)
.Map(cs =>
{
cs.MapLeftKey("AID");
cs.MapRightKey("BID");
cs.ToTable("AB");
});
}
Now things are perfectly fine, but how do I insert in this AB Mapping table?
If I try to create AB as like below, it generates two tables, AB and AB1 with same column name and all.
public class AB
{
public int ABID { get; set; }
public string AID { get; set; }
public int BID { get; set; }
}
So is there any way to do CRUD in FluentAPI Mapping Table?
If not, then can I force FluentAPI to map from Existing table? In this case I'll manually manage Employee and will change the mapping code to use existing table.
I'm unable to find any of the solution.

Answer 1

Edit: Since the question was changed, I'm writing up a more thorough answer. The answer to your question remains the same, however:
Now things are perfectly fine, but how do I insert in this AB Mapping
table?
You don't!
This is exactly the kind of thing that EF is good at. Instead of managing a link table yourself, now you just end up with the actual object you want. So, if you want to add a link between an A and B, all you do is add a B to the Bs collection on that A. You don't ever insert directly into the AB table, because who cares about that? That table is there so we can have relationships between different As and Bs, that's it. So, Entity Framework will create the table for it's own use, but not present it to you, because that's not how EF works: you work with your objects and let EF handle the database.
That's why when you try to define the table yourself, it creates two: it's already making a table called AB, but you're asking for another one. It can't have exactly the same name so it appends a '1' to the end of it. Since you've already used FluentAPI to define the apping, let EF worry about how to implement the mapping: all you need to care about is that you've now got a way to have an A with a set of Bs, or vice versa.
Since this still sounds confusing with names 'A' and 'B', below is the Program class for a console app that will illustrate this; all you need to do is start a fresh console app, replace the Program class with this one, install the entity framework package, and run enable-migrations -enableautomaticmigrations -force. I recommend you use this to add some objects and relate them, and then go have a look at your database: you will see the 'AB' table, with records that were added. This might help explain it better.
class Program
{
static bool quit = false;
static void Main(string[] args)
{
string s = "Please select an option:" +
"\n1: Insert an A" +
"\n2: Insert a B" +
"\n3: Add a B to an A" +
"\n4: Add an A to a B" +
"\n5: Print all As" +
"\n6: Print all Bs" +
"\n7: Print AB Table" +
"\nx: Quit.";
while (!quit)
{
Console.WriteLine();
Console.WriteLine(s);
var k = Console.ReadKey();
DoStuff(k);
}
}
private static void DoStuff(ConsoleKeyInfo i)
{
switch (i.Key)
{
case ConsoleKey.D1:
//add an A
AddA(GetName());
break;
case ConsoleKey.D2:
//add a B
AddB(GetName());
break;
case ConsoleKey.D3:
// link a B to an A
LinkB(GetBtoLink(),GetAtoLink());
break;
case ConsoleKey.D4:
//link an A to an B
LinkA(GetAtoLink(), GetBtoLink());
break;
case ConsoleKey.D5:
// print As
WriteA();
break;
case ConsoleKey.D6:
//print Bs
WriteB();
break;
case ConsoleKey.D7:
// print AB
WriteAB();
break;
case ConsoleKey.X:
quit = true;
break;
}
}
private static int GetAtoLink()
{
string x;
int z;
do
{
Console.Clear();
Console.WriteLine("Please enter the ID of the A you want to use and then press enter.");
WriteA();
x = Console.ReadLine();
} while (!int.TryParse(x, out z));
return z;
}
private static int GetBtoLink()
{
string x;
int z;
do
{
Console.Clear();
Console.WriteLine("Please enter the ID of the B you want to use and then press enter.");
WriteB();
x = Console.ReadLine();
} while (!int.TryParse(x, out z));
return z;
}
private static void WriteB()
{
Console.WriteLine("{0,10}{1,15}", "ID", "Name");
using (var db = new Context())
{
foreach (var a in db.Bs)
{
Console.WriteLine("{0,10}{1,15}", a.BID, a.Name);
}
}
}
private static void WriteA()
{
Console.WriteLine("{0,10}{1,15}", "ID", "Name");
using (var db = new Context())
{
foreach (var a in db.As)
{
Console.WriteLine("{0,10}{1,15}", a.AID, a.Name);
}
}
}
private static void WriteAB()
{
Console.WriteLine("{0,10}{1,10}", "AID", "BID");
using (var db = new Context())
{
// this is the only way we need to do this, because it's many to many,
// if an A is linked to a B, then that B is by definition linked to that A as well.
foreach (var a in db.As)
{
foreach (var b in a.Bs)
{
Console.WriteLine("{0,10}{1,10}", a.AID, b.BID);
}
}
}
}
private static void LinkB(int bToUse, int aToUse)
{
using (var db = new Context())
{
var a = db.As.First(x => x.AID == aToUse);
var b = db.Bs.First(y => y.BID == bToUse);
a.Bs.Add(b);
db.SaveChanges();
}
}
private static void LinkA(int aToUse, int bToUse)
{
using (var db = new Context())
{
var a = db.As.First(x => x.AID == aToUse);
var b = db.Bs.First(y => y.BID == bToUse);
b.As.Add(a);
db.SaveChanges();
}
}
private static string GetName()
{
Console.WriteLine("Please enter a name");
return Console.ReadLine();
}
private static void AddA(string input)
{
using (var db = new Context())
{
db.As.Add(new A {Name = input});
db.SaveChanges();
}
}
private static void AddB(string input)
{
using (var db = new Context())
{
db.Bs.Add(new B { Name = input });
db.SaveChanges();
}
}
}
public class A
{
public int AID { get; set; }
public string Name { get; set; }
public virtual ICollection<B> Bs { get; set; }
}
public class B
{
public int BID { get; set; }
public string Name { get; set; }
public virtual ICollection<A> As { get; set; }
}
public class Context : DbContext
{
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
base.OnModelCreating(modelBuilder);
modelBuilder.Entity<B>()
.HasMany(s => s.As)
.WithMany(c => c.Bs)
.Map(cs =>
{
cs.MapLeftKey("AID");
cs.MapRightKey("BID");
cs.ToTable("AB");
});
}
public DbSet<A> As { get; set; }
public DbSet<B> Bs { get; set; }
}
Old Answer: You've defined an ICollection<ApplicationUser> called Employees in Company, and mapped to it with FluentAPI. This creates a table called 'Employees' as expected. You don't have to create another class called Employees; as far as Entity Framework is concerned, you've already told it to create a table called Employees. This is why
I think the step you're missing is defining your DbSet<>.
Using your code, and running Add-Migration, this is the definition I get for the Employees table:
CreateTable(
"dbo.Employees",
c => new
{
UserID = c.Int(nullable: false),
CompanyID = c.Int(nullable: false),
})
.PrimaryKey(t => new { t.UserID, t.CompanyID })
.ForeignKey("dbo.ApplicationUsers", t => t.UserID, cascadeDelete: true)
.ForeignKey("dbo.Companies", t => t.CompanyID, cascadeDelete: true)
.Index(t => t.UserID)
.Index(t => t.CompanyID);
Which seems to correlate with what you wanted.
To finish it off, add (if you haven't already) this to your ApplicationDbContext file:
public DbSet<ApplicationUser> Employees;
public DbSet<Company> Companies;
Then to add an employee, you create a new ApplicationUser and add it like
ApplicationUser user = new ApplicationUser();
// do whatever here to give it the right data
ApplicationDbContext ctx = new ApplicationDbContext();
ctx.Employees.Add(user);
The Employees table itself you shouldn't ever have to interact with.

Answer 2

EF will manage that you don't need to insert into the mapping table directly, have a look at this sample that I have in my project:
public class Organization : Entity<int>
{
public string Name { get; set; }
public string Address { get; set; }
public string MainContact { get; set; }
public string Phone { get; set; }
public string Website { get; set; }
//navigation property
public virtual ICollection<DevelopmentalGoal> DevelopmentalGoals { get; set; }
public virtual ICollection<ServiceActivity> ServiceActivities { get; set; }
}
public class DevelopmentalGoal : Entity<int>
{
public string Name { get; set; }
public string Icon { get; set; }
//navigation property
public virtual ICollection<Organization> Organizations { get; set; }
}
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
modelBuilder.Entity<Organization>().ToTable("Organization", "ServiceLearning")
.HasKey(t => t.ID);
modelBuilder.Entity<DevelopmentalGoal>().ToTable("DevelopmentalGoal", "ServiceLearning")
.HasKey(t => t.ID);
modelBuilder.Entity<Organization>()
.HasMany(t => t.DevelopmentalGoals)
.WithMany(t=> t.Organizations)
.Map(m =>
{
m.ToTable("OrganizationDevelopmentalGoal", "ServiceLearning");
m.MapLeftKey("OrganizationID");
m.MapRightKey("DevelopmentalGoalID");
});
}
public int SaveOrganization(OrganizationViewModel viewModel, IUserContext currentUser)
{
Organization organization;
{
if (viewModel.ID == 0)
{
organization = ObjectMapper.MapTo<Organization>(viewModel);
_context.Set<Organization>().Add(organization);
}
else
{
organization = _context.Set<Organization>()
.SingleOrDefault(t =>
t.ID == viewModel.ID
);
organization.Name = viewModel.Name;
organization.Address = viewModel.Address;
organization.MainContact = viewModel.MainContact;
organization.Phone = viewModel.Phone;
organization.Website = viewModel.Website;
UpdateOrganizationDevelopmentalGoals(organization, viewModel);
}
try
{
CommitChanges();
}
catch (DbUpdateException ex)
{
if (ex.IsDuplicateException())
throw new KeystoneDuplicateException("A Organization with the same name already exists.");
throw ex;
}
}
return organization.ID;
}
private void UpdateOrganizationDevelopmentalGoals(Organization organization, OrganizationViewModel viewModel)
{
var originalIdList = organization.DevelopmentalGoals.Select(d => d.ID).Distinct().ToList();
var modifiedIdList = viewModel.DevelopmentalGoal.Where(d => d.Selected == true).Select(d => d.ID).Distinct().ToList();
//Remove deleted Developmetal Goals.
foreach (var id in originalIdList.Except(modifiedIdList))
organization.DevelopmentalGoals.Remove(organization.DevelopmentalGoals.Single(d => d.ID == id));
//Add new Developmetal Goals.
foreach (var id in modifiedIdList.Except(originalIdList))
{
//Add director relationship without having to load entity.
var d = new DevelopmentalGoal { ID = id };
_context.Set<DevelopmentalGoal>().Attach(d);
organization.DevelopmentalGoals.Add(d);
}
}
As you can see in the UpdateOrganizationDevelopmentalGoals method I do not insert or delete data from the mapping table directly, I insert and delete from the organization.DevelopmentalGoals and as I've already defined the mapping table in fluent API on "OnModelCreating" then EF knows how to manage the relations.