How can I use Entity Framework 6 and my repository to delete multiple records? - asp.net-mvc

Question

I am using Entity Framework 6 and I have a repository looking like the following with the Add and Update methods removed to make it shorter:
public class GenericRepository<T> : IRepository<T> where T : class
{
public GenericRepository(DbContext dbContext)
{
if (dbContext == null)
throw new ArgumentNullException("An instance of DbContext is required to use this repository", "context");
DbContext = dbContext;
DbSet = DbContext.Set<T>();
}
protected DbContext DbContext { get; set; }
protected DbSet<T> DbSet { get; set; }
public virtual IQueryable<T> Find(Expression<Func<T, bool>> predicate)
{
return DbSet.Where<T>(predicate);
}
public virtual IQueryable<T> GetAll()
{
return DbSet;
}
public virtual T GetById(int id)
{
//return DbSet.FirstOrDefault(PredicateBuilder.GetByIdPredicate<T>(id));
return DbSet.Find(id);
}
public virtual void Delete(T entity)
{
DbEntityEntry dbEntityEntry = DbContext.Entry(entity);
if (dbEntityEntry.State != EntityState.Deleted)
{
dbEntityEntry.State = EntityState.Deleted;
}
else
{
DbSet.Attach(entity);
DbSet.Remove(entity);
}
}
public virtual void Delete(int id)
{
var entity = GetById(id);
if (entity == null) return; // not found; assume already deleted.
Delete(entity);
}
}
In my controller I call the repository like this:
public HttpResponseMessage DeleteTest(int id)
{
Test test = _uow.Tests.GetById(id);
if (test == null)
{
return Request.CreateResponse(HttpStatusCode.NotFound);
}
try
{
_uow.Tests.Delete(test);
_uow.Commit();
return Request.CreateResponse(HttpStatusCode.OK);
}
catch (Exception ex)
{
return Request.CreateErrorResponse(HttpStatusCode.BadRequest, ex);
}
}
This works for a single test but how can I delete for example all tests that have an examId column value of 1 being
that examId is one of the columns in the Test table.

Answer 1

You can create another delete method in your generic repository class, see below:
public virtual void Delete(Expression<Func<T, bool>> predicate)
{
IQueryable<T> query = DbSet.Where(predicate).AsQueryable();
foreach (T obj in query)
{
DbSet.Remove(obj);
}
}
Then you can use it like below, it will delete all records which Id equalsid.
_uow.Test.Delete(n => n.Id = id)

Answer 2

I'm not sure if EF is able to handle multiple delete now given a certain value, but the last time I did this I had to resort to a loop.
public HttpResponseMessage DeleteTest(int id)
{
var testList = _uow.Tests.GetAll().Where(o => o.Id == id);
if (testList.Count() == 0)
{
return Request.CreateResponse(HttpStatusCode.NotFound);
}
try
{
foreach (var test in testList)
{
_uow.Tests.Delete(test);
}
_uow.Commit();
return Request.CreateResponse(HttpStatusCode.OK);
}
catch (Exception ex)
{
return Request.CreateErrorResponse(HttpStatusCode.BadRequest, ex);
}
}
If the "test" table is a foreign table linked to a primary table on the "ID" column, you may want to consider doing a cascading delete in this case.

Answer 3

You can use RemoveRange()
public virtual void Delete(Expression<Func<T,bool>> predicate)
{
var query = Context.Set<T>().Where(predicate);
Context.Set<T>().RemoveRange(query);
}