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

I'm deleting several items from a table using Entity Framework. There isn't a 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 it with an extension method or helper, but somewhere we're still going to be doing a foreach, right?

Answers


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.


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

Example:

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

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();

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

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.


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

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

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 });

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>();

For EF 4.1,

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

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);
    }
}

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.


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.


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();
}

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(); 
}

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.


EF 6.=>

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

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;
    }

Best : in EF6 => .RemoveRange()

Example:

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

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();

Need Your Help

Is this how you go about calling your Dao's in your service layer?

java oop

In your service layer, say you have a method that does XX, is this how you would reference your Dao classes?