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Change name of generated Join table ( Many to Many ) - EF Core 5

How to change name of a join table that EF Core 5 Created ?
for example
public class Food
{
public int FoodId { get; set; }
public string Name { get; set; }
public string Description { get; set; }
public string Ingredients { get; set; }
public string PhotoPath { get; set; }
public ICollection<Menu> Menus { get; set; }
}
public class Menu
{
public int MenuId { get; set; }
[Column(TypeName = "date")]
public DateTime MenuDate { get; set; }
public bool IsPublished { get; set; }
public ICollection<Food> Foods { get; set; }
}
and the join table for this 2 entities named FoodMenu, I want to change it to something else..

You can use one of the UsingEntity method overloads, for instance UsingEntity(Action<EntityTypeBuilder>).
Since it is a relationship fluent configuration API, you first need HasMany + WithMany pair, e.g.
modelBuilder.Entity<Food>()
.HasMany(left => left.Menus)
.WithMany(right => right.Foods)
.UsingEntity(join => join.ToTable("TheDesiredName"));

The accepted answer is missing an important part I had to struggle with.
First, you need to install the package
Microsoft.EntityFrameworkCore.Relational
Then you can add the following in your OnModelCreating overridden method
modelBuilder.Entity<Food>()
.HasMany(left => left.Menus)
.WithMany(right => right.Foods)
.UsingEntity(join => join.ToTable("NameYouWish"));

EF Core 2.0 - Navigation properties can only participate in a single relationship

Let's say I have these models:
public class Component
{
public int Id { get; set; }
public string Name { get; set; }
public string Type { get; set; }
public List<ComponentUpdate> Updates { get; set; }
public ComponentUpdate LastUpdate { get; set; }
}
public class ComponentUpdate
{
public int Id { get; set; }
public DateTime Timestamp { get; set; }
public Component Component { get; set; }
public string Message { get; set; }
}
The reason I'm saving the LastUpdate field instead of manually pulling it according to the highest 'TimeStamp' is because of speed. It would be faster to store a reference instead of checking the entire list every request.
When I'm trying to migrate the DB it throws an error saying I cannot have my properties participate in more than a single relationship.
I'm mapping the relationships in my context class and I don't think I'm doing it right since I have ComponentUpdate.Component mapped twice.
I've looked on several solutions but some were outdated and some just did not fit this scenario.
Thanks for helping.
Edit
Mapping accordingly:
modelBuilder.Entity<Component>().HasMany(c => c.Updates).WithOne(u => u.Component);
modelBuilder.Entity<ComponentUpdate>().HasOne(u => u.Component).WithOne(c => c.LastUpdate);

The property 'x' is not a navigation property of entity type 'y'

I'm using EF Core with ASP Core 2.0. Using latest Identity framework. I get this exception on page All.
InvalidOperationException: The property 'User' is not a navigation property of entity type 'Gallery'. The 'Include(string)' method can only be used with a '.' separated list of navigation property names.
ApplicationUser looks like:
public class ApplicationUser : IdentityUser<Guid>
{
public ICollection<Gallery> Galleries { get; set; }
}
Entity Gallery looks like:
public class Gallery
{
public int Id { get; set; }
public Guid UserId { get; set; }
public string Title { get; set; }
public int? ArticleId { get; set; }
public string Photos { get; set; }
public DateTime CreatedAt { get; set; }
public DateTime UpdatedAt { get; set; }
public Article Article { get; set; }
public ApplicationUser User { get; set; }
[NotMapped]
public List<string> PhotosList
{
get { return Photos?.Split('|').ToList(); }
set { Photos = string.Join("|", value); }
}
}
Controller for View looks like:
public async Task<IActionResult> All()
{
var databaseContext = db.Galleries.Include(x => x.Article).Include(x => x.User);
return View(await databaseContext.ToListAsync());
}
I have no idea why it dont crash on Article..
Database is up-to-date.

add a ForeignKey attribute
using System.ComponentModel.DataAnnotations.Schema;
...
[ForeignKey("Article")]
public int? ArticleId { get; set; }
[ForeignKey("User")]
public Guid UserId { get; set; }
You can also put the attribute on the navigation property
[ForeignKey("UserId")]
public ApplicationUser User { get; set; }
Also, make sure your dbContext inherits from IdentityDbContext<ApplicationUser, ...>

You can run into this if you manually add extra properties to Models.
To troubleshoot it, run SQL Profiler and capture the RAW SQL, execute the SQL against the database and see why the query doesn't work, ie which property 'x' is not a navigation property of entity type 'y'.
Then go to the model and remove the extra property you added manually.
PS: If you don't have a SQL dB you can use another profiler. Alternatively just check the diffs in source control.

Entity Framework Core Self reference optional property

I am using Microsoft.EntityFrameworkCore.Sqlite v1.0.1.
This is my entity:
public class Category
{
public int CategoryId { get;set;}
public Category ParentCategory { get; set; }
public int? ParentCategoryId { get; set; }
public string Name { get; set; }
public DateTime DateCreated { get; set; }
public DateTime DateModified { get; set; }
}
So i need to configure ParentCategory as an optional property. How can i do this in EF core?
This is my fluent mapping until now:
modelBuilder.Entity<Category>(e =>
{
e.HasKey(c => c.CategoryId);
e.Property(c => c.DateCreated).ValueGeneratedOnAdd();
e.Property(c => c.DateModified).ValueGeneratedOnAddOrUpdate();
});

Your ParentCategoryId is already optional based on the fact that it is nullable. If it wasn't nullable, it would be required. You don't need to configure it further.
Note, you don't need to configure CategoryId as the Key for Category. It will be configured as the key because it already follows the naming convention for an entity key.

Entity Framework - How to access foreign key not listed in Model

I have the following two entities,
public class App
{
public int AppID { get; set; }
public string Business { get; set; }
public string ApName { get; set; }
public string FirstContact { get; set; }
}
public class Colleague
{
public int ColleagueID { get; set; }
public string FirstName { get; set; }
public string SecondName { get; set; }
public string EmailAddress { get; set; }
public int PhoneNumber { get; set; }
public virtual ICollection<App> Apps { get; set; }
}
in my SQL table this automatically created a foriegn key property for the App model that refers to the ColleagueID.
My issue is that since the foriegn key isn't mentioned in the actual model, how do i use it in queries? for example, i want to show all the apps where the foreign key matches that of the given colleague ID.

You're on a right track. You need to populate the foreign key for the App class. This is a perfect example of one-to-many relationship.
public class App
{
public int AppID { get; set; }
public string Business { get; set; }
public string ApName { get; set; }
public string FirstContact { get; set; }
[ForeignKey("Colleague")]
public int ColleagueId { get; set; }
public virtual Colleague Colleague { get; set; }
}
Then you can call App.CollegueId or App.Colleague.CollegueId anywhere you want.

well one solution is :
IQueryable<Apps> q = ctx.Colleagues.Where(x => x.ColleagueID == someId).
SelectMany(x => x.Apps);
you will not see the table backing Colleague in the generated SQL query. You'll get something like:
SELECT
[Extend1].[AppID] AS [AppID],
...
FROM [dbo].[Apps] AS [Extend1]
WHERE 123 = [Extend1].[Colleague_ColleagueID]
where Colleague_ColleagueID is handled by EF and only by EF
So, there is no need, for the reasons you give, to expose a FK in your class.

Also, if you don't want to use Data Annotations and want that Colleague be optional when you save App to DB, you can use Fluent Api. First, add ColleagueId FK property to your App class:
public class App
{
//...
public int? ColleagueId { get; set; }
}
And then override the OnModelCreating method on your Context:
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
modelBuilder.Entity<App>()
.HasOptional(a => a.Colleague)
.WithMany(c => c.Apps)
.HasForeignKey(a => a.ColleagueId);
}
Now, this way you can do this query:
int selectedColleagueId = 1;
var apps=context.Apps.Where(a => a.ColleagueId == selectedColleagueId);
However, as #tschmit007 shows in his answer you don't need to expose the FK if you want just searching for that value. FK property is very useful when you need to update a relationship, for example, when you may not have the Coleague object in memory, but you do have access to that object’s key value. With a foreign key property, you can simply use the key value without depending on having that instance in memory:
app.ColleagueId=3;
context.SaveChanges();