使用实体框架从仅外键表中删除行

Question

I have a table User { UserId, Name, Age } and License { LicenseId, Name, IsActive } . Also I have a table UserLicense { UserId, LicenseId } which connects both of these and has the record for all the users who hold a license. A user can hold multiple license and those appear as different rows in the UserLicense table.

Now I need to remove a particular license from the license table. I do not want to delete it outright, so I mark IsActive = false . However I do want to delete rows from the UserLicense table for that license Id.

I am using Entity Framework.

If it is a direct table, I would have done something like :

var lic = db.Licenses.Where(l => l.Id== licenseId).FirstorDefault();
db.Licenses.Remove(lic);
db.SaveChanges();

However since UserLicense is a table of foreign keys, Entity Framework does not allow me to access it directly using

public void DeleteLicensedUsers(Guid LicenseId)
{
    db.UserLicenses.Where()
}

because the model does not contain an independent table for UserLicense as it is only a table of foreign keys.

So how do I delete all rows of UserLicense table for a particular licenseId using Linq and EF6?

Answer 1

If your entity class (I guess User ), has navigation properties of type ICollection<Licence> by removing Licence from this collection you are actually removing items from UserLicense table. This is how Entity Framework handles many-to-many relationships in databases.

Answer 2

I faced a similar issue and you can solve it this way. I almost tend to avoid tables with just foreign keys and instead add another column to fix this issue.

var license = db.Licenses.Where(l => l.ID == LicenseId).FirstOrDefault();
var users = license.Users.ToList();


if (users != null)
{
    foreach (var user in users)
    {
         license.Users.Remove(user);
    }                   
}

Answer 3

I'm a little confused by your question. So if you mark a license as isActive = false , and still want to see that license appear on user's page, then there should still a record in UserLicense table associating the two.

That said, I believe this answer from a similar question will help you.

so essentially:

//include licenses in the user entity
var result = ctx.User.Include(x=>x.Licenses).Where(t=>t.Id == _id).FirstOrDefault()
//get the licenses you are looking for, either equal or use .Contains
var licensesOfUser = result.Where(x=>x.Licenses.Where(l=>l.id == _licenseId);
//remove them from entity and save.
result.Licenses.RemoveRange(licenseOfUser);
ctx.SaveChanges();

[edit: if you have license]

//include users in license entities  
var result = ctx.License.Include(x=>x.Users).Where(t=>t.Id == _id).FirstOrDefault()
//get the users you are looking for, either equal or use .Contains
var usersOfLicenses = result.Where(x=>x.Users.Where(l=>l.id == _userId);
//remove them from entity and save.
result.Users.RemoveRange(licenseOfUser);
ctx.SaveChanges();