C# 我应该如何删除 DbSet 中的所有元素？
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/10448684/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
How should I remove all elements in a DbSet?
提问by aknuds1
What's the best way to remove all elements in a System.Data.Entity.DbSet, with Entity Framework 4.3?
使用 Entity Framework 4.3 删除 System.Data.Entity.DbSet 中所有元素的最佳方法是什么？
采纳答案by Slauma
dbContext.Database.ExecuteSqlCommand("delete from MyTable");
(No kidding.)
（不开玩笑。）
The problem is that EF doesn't support any batch commands and the only way to delete all entities in a set using no direct DML would be:
问题是 EF 不支持任何批处理命令，不使用直接 DML 删除集合中所有实体的唯一方法是：
foreach (var entity in dbContext.MyEntities)
dbContext.MyEntities.Remove(entity);
dbContext.SaveChanges();
Or maybe a litte bit cheaper to avoid loading full entities:
或者可能便宜一点以避免加载完整的实体：
foreach (var id in dbContext.MyEntities.Select(e => e.Id))
{
var entity = new MyEntity { Id = id };
dbContext.MyEntities.Attach(entity);
dbContext.MyEntities.Remove(entity);
}
dbContext.SaveChanges();
But in both cases you have to load allentities or allkey properties and remove the entities one by one from the set. Moreover when you call SaveChangesEF will send n (=number of entities in the set) DELETE statements to the database which also get executed one by one in the DB (in a single transaction).
但在这两种情况下，您都必须加载所有实体或所有关键属性，并从集合中一一删除实体。此外，当您调用SaveChangesEF 时，将向数据库发送 n 个（=集合中的实体数）DELETE 语句，这些语句也将在 DB 中（在单个事务中）一一执行。
So, direct SQL is clearly preferable for this purpose as you only need a single DELETE statement.
因此，出于此目的，直接 SQL 显然更可取，因为您只需要一个 DELETE 语句。
回答by Tim Cooke
Here's another way you can do it in code.
这是您可以在代码中执行此操作的另一种方法。
public static class Extensions
{
public static void DeleteAll<T>(this DbContext context)
where T : class
{
foreach (var p in context.Set<T>())
{
context.Entry(p).State = EntityState.Deleted;
}
}
}
To actually call the method and clear the set:
要实际调用该方法并清除该集合：
myDbContext.DeleteAll<MyPocoClassName>();
回答by Fred Johnson
If you are working with a unit of work and generic repository you may find the following useful
如果您正在使用工作单元和通用存储库，您可能会发现以下有用
public virtual void DeleteWhere(Expression<Func<TEntity, bool>> filter = null,
Func<IQueryable<TEntity>, IOrderedQueryable<TEntity>> orderBy = null,
string includeProperties = "")
{
IQueryable<TEntity> query = dbSet;
if (filter != null)
{
query = query.Where(filter);
}
foreach (var includeProperty in includeProperties.Split
(new char[] { ',' }, StringSplitOptions.RemoveEmptyEntries))
{
query = query.Include(includeProperty);
}
foreach (var entity in query)
{
context.Entry(entity).State = EntityState.Deleted;
}
}
Usage:
用法：
uow.myRepositoryName.DeleteWhere(u => u.RoomId == roomId);
uow.Save();
回答by Anestis Kivranoglou
If you want to remove all elements without writing any SQLand only execute a Single Db Call
如果你想在不写任何 SQL 的情况下删除所有元素并且只执行一个Single Db Call
Entity Framework Extended Libraryoffers a batch deletemethod.
实体框架扩展库提供了批量删除的方法。
context.Users.Delete();
回答by Ravindra Devrani
You can achieve it by using a direct query:
您可以通过使用直接查询来实现它：
ent.Database.ExecuteSqlCommand("delete from tablename");
回答by Ryfcia
As the accepted answer only mentions about the method below:
由于接受的答案仅提及以下方法：
context.Database.ExecuteSqlCommand("delete from MyTable");
and rather gives alternatives to it, I've managed to write a method, which you can use to avoid loading all entities, then looping through them and use ExecuteSqlCommandinstead.
而是提供了替代方案，我设法编写了一个方法，您可以使用它来避免加载所有实体，然后循环遍历它们并改用ExecuteSqlCommand。
Assuming using unit of work, where context is DbContext:
假设使用工作单元，其中上下文是 DbContext：
using System.Data.Entity.Core.Objects;
using System.Text.RegularExpressions;
public void DeleteAll()
{
ObjectContext objectContext = ( (IObjectContextAdapter)context ).ObjectContext;
string sql = objectContext.CreateObjectSet<T>().ToTraceString();
Regex regex = new Regex( "FROM (?<table>.*) AS" );
Match match = regex.Match( sql );
string tableName = match.Groups[ "table" ].Value;
context.Database.ExecuteSqlCommand( string.Format( "delete from {0}", tableName ) );
}
First block of code retrievs the table name needed in ExecuteSqlCommandmethod.
第一个代码块检索ExecuteSqlCommand方法中所需的表名。
Usage:
用法：
using ( var context = new UnitOfWork() )
{
context.MyRepository.DeleteAll();
}
There's no needto call
有没有必要打电话
context.SaveChanges()
回答by joeystdio
Old post but there is a RemoveRange method now:
旧帖子，但现在有一个 RemoveRange 方法：
dbContext.MyEntities.RemoveRange(dbContext.MyEntities);
dbContext.SaveChanges();
