[英]How can I use Entity Framework 6 and my repository to delete multiple records?
我正在使用Entity Framework 6,並且具有一個類似於以下內容的存儲庫,其中刪除了Add和Update方法以使其更短:
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);
}
}
在我的控制器中,我這樣調用存儲庫:
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);
}
}
這適用於單個測試,但是如何刪除例如examsId列值為1的所有測試,因為examId是Test表中的列之一。
您可以在通用存儲庫類中創建另一個delete方法,請參見下文:
public virtual void Delete(Expression<Func<T, bool>> predicate)
{
IQueryable<T> query = DbSet.Where(predicate).AsQueryable();
foreach (T obj in query)
{
DbSet.Remove(obj);
}
}
然后您可以像下面一樣使用它,它將刪除所有Id
等於id
記錄。
_uow.Test.Delete(n => n.Id = id)
我不確定在給定一定值的情況下EF是否能夠處理多次刪除,但是我上一次這樣做時,我不得不求助於循環。
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);
}
}
如果“測試”表是鏈接到“ ID”列上主表的外部表,則在這種情況下,您可能需要考慮進行級聯刪除。
您可以使用RemoveRange()
public virtual void Delete(Expression<Func<T,bool>> predicate)
{
var query = Context.Set<T>().Where(predicate);
Context.Set<T>().RemoveRange(query);
}
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