How do I delete multiple rows in Entity Framework (without foreach)

Question

I want to delete several items from a table using Entity Framework. There is no foreign key / parent object, so I can't handle this with OnDeleteCascade.

Right now I'm doing this:

var widgets = context.Widgets
    .Where(w => w.WidgetId == widgetId);

foreach (Widget widget in widgets)
{
    context.Widgets.DeleteObject(widget);
}
context.SaveChanges();

It works, but the foreach bugs me. I'm using EF4, but I don't want to execute SQL. I just want to make sure I'm not missing anything -- this is as good as it gets, right? I can abstract the code with an extension method or helper, but somewhere we're still going to be doing a foreach, right?

Answer 1

EntityFramework 6 has made this a bit easier with .RemoveRange().

Example:

db.People.RemoveRange(db.People.Where(x => x.State == "CA"));
db.SaveChanges();

Warning! Do not use this on large datasets!

EF pulls all the data into memory, THEN deletes it. For smaller data sets this might not be an issue but generally avoid this style of delete unless you can guarantee you are only doing very small changes.

You could easily run your process out of memory while EF happily pulls in all the data you specified just to delete it.

Answer 2

using (var context = new DatabaseEntities())
{
    context.ExecuteStoreCommand("DELETE FROM YOURTABLE WHERE CustomerID = {0}", customerId);
}

Addition: To support list of ids you can write

var listOfIds = String.Join(',',customerIds.Select(id => $"'{id}'").ToList());
var sql= $@"DELETE  [YOURTABLE] WHERE CustomerID in ({listOfIds})";

Note: if CustomerID Is a string, you should double-check for potential SQL injection risks, for integer CustomerID it’s safe

Answer 3

this is as good as it gets, right? I can abstract it with an extension method or helper, but somewhere we're still going to be doing a foreach, right?

Well, yes, except you can make it into a two-liner:

context.Widgets.Where(w => w.WidgetId == widgetId)
               .ToList().ForEach(context.Widgets.DeleteObject);
context.SaveChanges();

Answer 4

I know it's quite late but in case someone needs a simple solution, the cool thing is you can also add the where clause with it:

public static void DeleteWhere<T>(this DbContext db, Expression<Func<T, bool>> filter) where T : class
{
    string selectSql = db.Set<T>().Where(filter).ToString();
    string fromWhere = selectSql.Substring(selectSql.IndexOf("FROM"));
    string deleteSql = "DELETE [Extent1] " + fromWhere;
    db.Database.ExecuteSqlCommand(deleteSql);
}

Note: just tested with MSSQL2008.

Update:

The solution above won't work when EF generates sql statement with parameters, so here's the update for EF5:

public static void DeleteWhere<T>(this DbContext db, Expression<Func<T, bool>> filter) where T : class
{
    var query = db.Set<T>().Where(filter);
    
    string selectSql = query.ToString();
    string deleteSql = "DELETE [Extent1] " + selectSql.Substring(selectSql.IndexOf("FROM"));

    var internalQuery = query.GetType().GetFields(BindingFlags.NonPublic | BindingFlags.Instance).Where(field => field.Name == "_internalQuery").Select(field => field.GetValue(query)).First();
    var objectQuery = internalQuery.GetType().GetFields(BindingFlags.NonPublic | BindingFlags.Instance).Where(field => field.Name == "_objectQuery").Select(field => field.GetValue(internalQuery)).First() as ObjectQuery;
    var parameters = objectQuery.Parameters.Select(p => new SqlParameter(p.Name, p.Value)).ToArray();

    db.Database.ExecuteSqlCommand(deleteSql, parameters);
}
        

It requires a little bit of reflection but works well.

Further update for EF Core 6 I modified it to this, no reflection.

public void RemoveWhere<T>(DbContext db, Expression<Func<T, bool>> filter) where T : class
{
    string selectSql = db.Set<T>().Where(filter).ToQueryString();
    int fromIndex = selectSql.IndexOf("FROM");
    int whereIndex = selectSql.IndexOf("WHERE");

    string fromSql = selectSql.Substring(fromIndex, whereIndex - fromIndex);
    string whereSql = selectSql.Substring(whereIndex);
    string aliasSQl = fromSql.IndexOf(" AS ") > -1 ? fromSql.Substring(fromSql.IndexOf(" AS ") + 4) : "";
    string deleteSql = string.Join(" ", "DELETE ", aliasSQl.Trim(), fromSql.Trim(), whereSql.Trim());
    db.Database.ExecuteSqlRaw(deleteSql);
}

Answer 5

If you don't want to execute SQL directly calling DeleteObject in a loop is the best you can do today.

However you can execute SQL and still make it completely general purpose via an extension method, using the approach I describe here.

Although that answer was for 3.5. For 4.0 I would probably use the new ExecuteStoreCommand API under the hood, instead of dropping down to the StoreConnection.

Answer 6

For anyone using EF5, following extension library can be used: https://github.com/loresoft/EntityFramework.Extended

context.Widgets.Delete(w => w.WidgetId == widgetId);

Answer 7

Entity Framework Core

3.1 3.0 2.2 2.1 2.0 1.1 1.0

using (YourContext context = new YourContext ())
{
    var widgets = context.Widgets.Where(w => w.WidgetId == widgetId);
    context.Widgets.RemoveRange(widgets);
    context.SaveChanges();
}

Summary:

Removes the given collection of entities from the context underlying the set with each entity being put into the Deleted state such that it will be deleted from the database when SaveChanges is called.

Remarks:

Note that if System.Data.Entity.Infrastructure.DbContextConfiguration.AutoDetectChangesEnabled is set to true (which is the default), then DetectChanges will be called once before delete any entities and will not be called again. This means that in some situations RemoveRange may perform significantly better than calling Remove multiple times would do. Note that if any entity exists in the context in the Added state, then this method will cause it to be detached from the context. This is because an Added entity is assumed not to exist in the database such that trying to delete it does not make sense.

Answer 8

Finally bulk delete has been introduced in Entity Framework Core 7 via the ExecuteDelete command:

context.Widgets
    .Where(w => w.WidgetId == widgetId)
    .ExecuteDelete();

Something to note here is that ExecuteDelete does not need a SaveChanges, as per its documentation:

This operation executes immediately against the database, rather than being deferred until DbContext.SaveChanges() is called. It also does not interact with the EF change tracker in any way: entity instances which happen to be tracked when this operation is invoked aren't taken into account, and aren't updated to reflect the changes.

I know that the question was asked for EF4, but if you upgrade this is a good alternative!

Answer 9

Still seems crazy to have to pull anything back from the server just to delete it, but at least getting back just the IDs is a lot leaner than pulling down the full entities:

var ids = from w in context.Widgets where w.WidgetId == widgetId select w.Id;
context.Widgets.RemoveRange(from id in ids.AsEnumerable() select new Widget { Id = id });

Answer 10

This answers is for EF Core 7 (I am not aware if they merged EF Core with EF now or not, before they kept the two separately).

EF Core 7 now supports ExecuteUpdate and ExecuteDelete (Bulk updates):

// Delete all Tags (BE CAREFUL!)
await context.Tags.ExecuteDeleteAsync();

// Delete Tags with a condition
await context.Tags.Where(t => t.Text.Contains(".NET")).ExecuteDeleteAsync();

The equivalent SQL queries are:

DELETE FROM [t]
FROM [Tags] AS [t]

DELETE FROM [t]
FROM [Tags] AS [t]
WHERE [t].[Text] LIKE N'%.NET%'

Answer 11

EF 6.1

public void DeleteWhere<TEntity>(Expression<Func<TEntity, bool>> predicate = null) 
where TEntity : class
{
    var dbSet = context.Set<TEntity>();
    if (predicate != null)
        dbSet.RemoveRange(dbSet.Where(predicate));
    else
        dbSet.RemoveRange(dbSet);

    context.SaveChanges();
} 

Usage:

// Delete where condition is met.
DeleteWhere<MyEntity>(d => d.Name == "Something");

Or:

// delete all from entity
DeleteWhere<MyEntity>();

Answer 12

For EF 4.1,

var objectContext = (myEntities as IObjectContextAdapter).ObjectContext;
objectContext.ExecuteStoreCommand("delete from [myTable];");

Answer 13

The quickest way to delete is using a stored procedure. I prefer stored procedures in a database project over dynamic SQL because renames will be handled correctly and have compiler errors. Dynamic SQL could refer to tables that have been deleted/renamed causing run time errors.

In this example, I have two tables List and ListItems. I need a fast way to delete all the ListItems of a given list.

CREATE TABLE [act].[Lists]
(
    [Id] INT NOT NULL PRIMARY KEY IDENTITY, 
    [Name] NVARCHAR(50) NOT NULL
)
GO
CREATE UNIQUE INDEX [IU_Name] ON [act].[Lists] ([Name])
GO
CREATE TABLE [act].[ListItems]
(
    [Id] INT NOT NULL IDENTITY, 
    [ListId] INT NOT NULL, 
    [Item] NVARCHAR(100) NOT NULL, 
    CONSTRAINT PK_ListItems_Id PRIMARY KEY NONCLUSTERED (Id),
    CONSTRAINT [FK_ListItems_Lists] FOREIGN KEY ([ListId]) REFERENCES [act].[Lists]([Id]) ON DELETE CASCADE
)
go
CREATE UNIQUE CLUSTERED INDEX IX_ListItems_Item 
ON [act].[ListItems] ([ListId], [Item]); 
GO

CREATE PROCEDURE [act].[DeleteAllItemsInList]
    @listId int
AS
    DELETE FROM act.ListItems where ListId = @listId
RETURN 0

Now the interesting part of deleting the items and updating Entity framework using an extension.

public static class ListExtension
{
    public static void DeleteAllListItems(this List list, ActDbContext db)
    {
        if (list.Id > 0)
        {
            var listIdParameter = new SqlParameter("ListId", list.Id);
            db.Database.ExecuteSqlCommand("[act].[DeleteAllItemsInList] @ListId", listIdParameter);
        }
        foreach (var listItem in list.ListItems.ToList())
        {
            db.Entry(listItem).State = EntityState.Detached;
        }
    }
}

The main code can now use it is as

[TestMethod]
public void DeleteAllItemsInListAfterSavingToDatabase()
{
    using (var db = new ActDbContext())
    {
        var listName = "TestList";
        // Clean up
        var listInDb = db.Lists.Where(r => r.Name == listName).FirstOrDefault();
        if (listInDb != null)
        {
            db.Lists.Remove(listInDb);
            db.SaveChanges();
        }

        // Test
        var list = new List() { Name = listName };
        list.ListItems.Add(new ListItem() { Item = "Item 1" });
        list.ListItems.Add(new ListItem() { Item = "Item 2" });
        db.Lists.Add(list);
        db.SaveChanges();
        listInDb = db.Lists.Find(list.Id);
        Assert.AreEqual(2, list.ListItems.Count);
        list.DeleteAllListItems(db);
        db.SaveChanges();
        listInDb = db.Lists.Find(list.Id);
        Assert.AreEqual(0, list.ListItems.Count);
    }
}

Answer 14

You can use extensions libraries for doing that like EntityFramework.Extended or Z.EntityFramework.Plus.EF6, there are available for EF 5, 6 or Core. These libraries have great performance when you have to delete or update and they use LINQ. Example for deleting (source plus):

ctx.Users.Where(x => x.LastLoginDate < DateTime.Now.AddYears(-2)) .Delete();

or (source extended)

context.Users.Where(u => u.FirstName == "firstname") .Delete();

These use native SQL statements, so performance is great.

Answer 15

If you want to delete all rows of a table, you can execute sql command

using (var context = new DataDb())
{
     context.Database.ExecuteSqlCommand("TRUNCATE TABLE [TableName]");
}

TRUNCATE TABLE (Transact-SQL) Removes all rows from a table without logging the individual row deletions. TRUNCATE TABLE is similar to the DELETE statement with no WHERE clause; however, TRUNCATE TABLE is faster and uses fewer system and transaction log resources.

Answer 16

You can execute sql queries directly as follows :

    private int DeleteData()
{
    using (var ctx = new MyEntities(this.ConnectionString))
    {
        if (ctx != null)
        {

            //Delete command
            return ctx.ExecuteStoreCommand("DELETE FROM ALARM WHERE AlarmID > 100");

        }
    }
    return 0;
}

For select we may use

using (var context = new MyContext()) 
{ 
    var blogs = context.MyTable.SqlQuery("SELECT * FROM dbo.MyTable").ToList(); 
}

Answer 17

UUHHIVS's is a very elegant and fast way for batch delete, but it must be used with care:

• auto generation of transaction: its queries will be encompassed by a transaction
• database context independence: its execution has nothing to do with context.SaveChanges()

These issues can be circumvented by taking control of the transaction. The following code illustrates how to batch delete and bulk insert in a transactional manner:

var repo = DataAccess.EntityRepository;
var existingData = repo.All.Where(x => x.ParentId == parentId);  

TransactionScope scope = null;
try
{
    // this starts the outer transaction 
    using (scope = new TransactionScope(TransactionScopeOption.Required))
    {
        // this starts and commits an inner transaction
        existingData.Delete();

        // var toInsert = ... 

        // this relies on EntityFramework.BulkInsert library
        repo.BulkInsert(toInsert);

        // any other context changes can be performed

        // this starts and commit an inner transaction
        DataAccess.SaveChanges();

        // this commit the outer transaction
        scope.Complete();
    }
}
catch (Exception exc)
{
    // this also rollbacks any pending transactions
    scope?.Dispose();
}

Answer 18

In EF 7 you can use bulk delete

    var ids = widgets.Select(x => x.Id).ToList();
    await _mrVodDbContext.Widgets.Where(x => ids.Contains(x.Id)).ExecuteDeleteAsync();

EF core generate

  DELETE FROM [i]
  FROM [Widgets] AS [i]
  WHERE [i].[Id] IN (4,3,2,1)

More about deleting or updating in release notes. https://learn.microsoft.com/en-us/ef/core/what-is-new/ef-core-7.0/whatsnew#basic-executedelete-examples

Answer 19

You can also use the DeleteAllOnSubmit() method by passing it your results in a generic list rather than in var. This way your foreach reduces to one line of code:

List<Widgets> widgetList = context.Widgets
              .Where(w => w.WidgetId == widgetId).ToList<Widgets>();

context.Widgets.DeleteAllOnSubmit(widgetList);

context.SubmitChanges();

It probably still uses a loop internally though.

Answer 20

Thanh's answer worked best for me. Deleted all my records in a single server trip. I struggled with actually calling the extension method, so thought I would share mine (EF 6):

I added the extension method to a helper class in my MVC project and changed the name to "RemoveWhere". I inject a dbContext into my controllers, but you could also do a using.

// make a list of items to delete or just use conditionals against fields
var idsToFilter = dbContext.Products
    .Where(p => p.IsExpired)
    .Select(p => p.ProductId)
    .ToList();

// build the expression
Expression<Func<Product, bool>> deleteList = 
    (a) => idsToFilter.Contains(a.ProductId);

// Run the extension method (make sure you have `using namespace` at the top)
dbContext.RemoveWhere(deleteList);

This generated a single delete statement for the group.

Answer 21

I came up with a great library Zack.EFCore.Batch. It will convert your expression into simple DELETE FROM .... WHERE query. (Like some answers proposed) https://github.com/yangzhongke/Zack.EFCore.Batch

The usage example:

await ctx.DeleteRangeAsync<Book>(b => b.Price > n);

The Zack.EFCore.Batch library has lots of benefits over Z.EntityFramework.Extended https://entityframework-extensions.net/ which does not have true Async methods. (They are just wrappers around sync methods) You can get lots of unexpected issues by using this library in high load environment.

Answer 22

EF 6.=>

var assignmentAddedContent = dbHazirBot.tbl_AssignmentAddedContent.Where(a =>
a.HazirBot_CategoryAssignmentID == categoryAssignment.HazirBot_CategoryAssignmentID);
dbHazirBot.tbl_AssignmentAddedContent.RemoveRange(assignmentAddedContent);
dbHazirBot.SaveChanges();

Answer 23

Best : in EF6 => .RemoveRange()

Example:

db.Table.RemoveRange(db.Table.Where(x => Field == "Something"));

Answer 24

 context.Widgets.RemoveRange(context.Widgets.Where(w => w.WidgetId == widgetId).ToList());
                db.SaveChanges();

Answer 25

If you are using Generic Repository:

Inside Generic repository, following could be new method.

       public void RemoveMultiple(Expression<Func<T, bool>> predicate)
        {
             IQueryable<T> query = _context.Set<T>().Where(predicate);
             _context.Set<T>().RemoveRange(query.AsNoTracking());
            
        }

Usage:

_unitOfWork.YOUR_ENTITY.RemoveMultiple(x => x.AccountId == accountId);
 _unitOfWork.Complete();

Answer 26

See the answer 'favorite bit of code' that works

Here is how I used it:

     // Delete all rows from the WebLog table via the EF database context object
    // using a where clause that returns an IEnumerable typed list WebLog class 
    public IEnumerable<WebLog> DeleteAllWebLogEntries()
    {
        IEnumerable<WebLog> myEntities = context.WebLog.Where(e => e.WebLog_ID > 0);
        context.WebLog.RemoveRange(myEntities);
        context.SaveChanges();

        return myEntities;
    }

Answer 27

In EF 6.2 this works perfectly, sending the delete directly to the database without first loading the entities:

context.Widgets.Where(predicate).Delete();

With a fixed predicate it's quite straightforward:

context.Widgets.Where(w => w.WidgetId == widgetId).Delete();

And if you need a dynamic predicate have a look at LINQKit (Nuget package available), something like this works fine in my case:

Expression<Func<Widget, bool>> predicate = PredicateBuilder.New<Widget>(x => x.UserID == userID);
if (somePropertyValue != null)
{
    predicate = predicate.And(w => w.SomeProperty == somePropertyValue);
}
context.Widgets.Where(predicate).Delete();