We may require to delete all the records from the table using EF Core. In this article, we will check alternative options like running Truncate/Delete commands and unit testing options.
Background
Sometimes, we may require to delete all the records from the table using Entity Framework Core. One of the commonly used approaches is to iterate each row and use the DBSet<T>.Remove()
to delete each row as shown below:
foreach (var item in Db.Users)
{
Db.Users.Remove(item);
}
Db.SaveChanges();
This process is slower than Truncate
/Delete
and not suitable for large datasets. Here, are going to check alternative options, like running Truncate
/Delete
commands and unit testing options.
Clean Helper
The idea is to use a raw SQL query to Truncate
a table or Delete
everything from a table.
Annotation Helper
Annotation helper is to get table name and schema from entity framework mapping configuration of a model.
using Microsoft.EntityFrameworkCore;
using Microsoft.EntityFrameworkCore.Infrastructure;
using Microsoft.EntityFrameworkCore.Metadata;
namespace EfCoreHelper.Database.Core
{
public class AnnotationHelper
{
private static string GetName(IEntityType entityType,
string defaultSchemaName = "dbo")
{
var schema = entityType.FindAnnotation("Relational:Schema").Value;
string tableName = entityType.GetAnnotation
("Relational:TableName").Value.ToString();
string schemaName = schema == null ? defaultSchemaName : schema.ToString();
string name = string.Format("[{0}].[{1}]", schemaName, tableName);
return name;
}
public static string TableName<T>(DbContext dbContext) where T : class
{
var entityType = dbContext.Model.FindEntityType(typeof(T));
return GetName(entityType);
}
public static string TableName<T>(DbSet<T> dbSet) where T : class
{
var entityType = dbSet.EntityType;
return GetName(entityType);
}
}
}
Extension Methods
Along with Microsoft.EntityFrameworkCore
, we need to install Microsoft.EntityFrameworkCore.Relational
. This will enable us to use ExecuteSqlRaw()
to run row query in Entity Framework Core.
Install-Package Microsoft.EntityFrameworkCore
Install Microsoft.EntityFrameworkCore.Relational
Here are the extension methods for both DbSet<T>
and DbContext
:
Truncate
- Truncates a table using a truncate
query Delete
- Delete all rows of a table using a delete
query Clear
- Delete all rows of a table using RemoveRange
method
using Microsoft.EntityFrameworkCore;
using Microsoft.EntityFrameworkCore.Infrastructure;
using System.Linq;
namespace EfCoreHelper.Database.Core
{
public static class EfCleanHelper
{
public static string Truncate<T>(this DbSet<T> dbSet) where T : class
{
string cmd = $"TRUNCATE TABLE {AnnotationHelper.TableName(dbSet)}";
var context = dbSet.GetService<ICurrentDbContext>().Context;
context.Database.ExecuteSqlRaw(cmd);
return cmd;
}
public static string Delete<T>(this DbSet<T> dbSet) where T : class
{
string cmd = $"DELETE FROM {AnnotationHelper.TableName(dbSet)}";
var context = dbSet.GetService<ICurrentDbContext>().Context;
context.Database.ExecuteSqlRaw(cmd);
return cmd;
}
public static void Clear<T>(this DbContext context) where T : class
{
DbSet<T> dbSet = context.Set<T>();
if (dbSet.Any())
{
dbSet.RemoveRange(dbSet.ToList());
}
}
public static void Clear<T>(this DbSet<T> dbSet) where T : class
{
if (dbSet.Any())
{
dbSet.RemoveRange(dbSet.ToList());
}
}
public static string Truncate(this DbContext context,
string tableName, string schemaName = "dbo")
{
string name = string.Format("[{0}].[{1}]", schemaName, tableName);
string cmd = $"TRUNCATE TABLE { name }";
context.Database.ExecuteSqlRaw(cmd);
return cmd;
}
public static string Delete(this DbContext context,
string tableName, string schemaName = "dbo")
{
string name = string.Format("[{0}].[{1}]", schemaName, tableName);
string cmd = $"DELETE FROM { name }";
context.Database.ExecuteSqlRaw(cmd);
return cmd;
}
}
}
Using the Code
Delete
Using Name
Db.Delete("Users");
Using DbSet<T>
Db.Users.Delete();
Use Transaction
using (var tran = Db.Database.BeginTransaction())
{
try
{
Db.Users.Delete();
tran.Commit();
}
catch (Exception ex)
{
tran.Rollback();
}
}
Truncate
Using Name
Db.Truncate("Users");
Using DbSet<T>
Db.Users.Truncate();
Clear
Using DbSet<T>
Db.Users.Clear();
Db.SaveChanges();
Using DbContext
Db.Clear<User>();
Db.SaveChanges();
Unit Testing
Let's add packages to the test project:
- Moq used for entity framework
DbContext
mocking - NBuilder to populate sample test data
Install-Package Nunit
Install-Package Moq
Install-Package NBuilder
Clear
methods are good for unit testing. But Truncate
and Delete
methods are running raw SQL, so for unit testing, we need to bypass them.
Add Things in Db Context
Here, the CpuAppDbContext
db context class is implementing the interface ICpuAppDbContext.
Which force to add void Truncate<T>() where T : class
and void Delete<T>() where T : class
methods, which will be used to truncate a table or delete data of a table. In the actual implemention, we are calling existing extension methods.
public interface ICpuAppDbContext : IDisposable
{
DbSet<User> Users { get; set; }
void Truncate<T>() where T : class;
void Delete<T>() where T : class;
DbSet<T> Set<T>() where T : class;
int SaveChanges();
}
public class CpuAppDbContext : DbContext, ICpuAppDbContext
{
public CpuAppDbContext(DbContextOptions<CpuAppDbContext> options) : base(options)
{
}
public CpuAppDbContext() : base()
{
}
public DbSet<User> Users { get; set; }
public void Truncate<T>() where T : class
{
this.Set<T>().Truncate();
}
public void Delete<T>() where T : class
{
this.Set<T>().Delete();
}
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
modelBuilder.ApplyConfiguration(new UserConfig());
}
}
Using Methods In Actual Code
Db.Delete<User>();
Db.Truncate<User>();
Test Methods
Helper method to convert a List<T>
to DbSet<T>
:
public static class TestHelpers
{
public static DbSet<T> ToDbSet<T>(this List<T> list) where T : class
{
IQueryable<T> queryableList = list.AsQueryable();
var mockSet = new Mock<DbSet<T>>();
mockSet.As<IQueryable<T>>().Setup(m =>
m.Provider).Returns(queryableList.Provider);
mockSet.As<IQueryable<T>>().Setup(m =>
m.Expression).Returns(queryableList.Expression);
mockSet.As<IQueryable<T>>().Setup(m =>
m.ElementType).Returns(queryableList.ElementType);
mockSet.As<IQueryable<T>>().Setup(m =>
m.GetEnumerator()).Returns(queryableList.GetEnumerator());
return mockSet.Object;
}
}
Unit Testing Using Interface
Here, we are bypassing/mocking the Delete
method:
[Test]
public void DbContext_Moq_Using_Interface()
{
List<User> users = Builder<User>.CreateListOfSize(10).Build().ToList();
bool isCalled = false;
var dbMock = new Mock<ICpuAppDbContext>();
dbMock.Setup(x => x.Users).Returns(users.ToDbSet());
dbMock.Setup(x => x.Delete<User>()).Callback(() =>
{
users = new List<User>();
isCalled = true;
});
ICpuAppDbContext db = dbMock.Object;
db.Delete<User>();
Assert.True(isCalled);
}
Unit Testing using DbContext Class
For mocking, we must declare testable dbsets and methods as virtual. This virtual thing is also related to Lazy and Eager loading. So be sure before using or making changes to existing codes. I do prefer interface based mocking, and it is the best option.
[Test]
public void DbContext_Moq_Using_Class()
{
List<User> users = Builder<User>.CreateListOfSize(10).Build().ToList();
bool isCalled = false;
var dbMock = new Mock<CpuAppDbContext>();
dbMock.Setup(x => x.Users).Returns(users.ToDbSet());
dbMock.Setup(x => x.Delete<User>()).Callback(() =>
{
users = new List<User>();
isCalled = true;
});
CpuAppDbContext db = dbMock.Object;
db.Delete<User>();
Assert.True(isCalled);
}
Assembly Faking
To mock extension methods, Fakes Assembly can also be used.
Moq.EntityFrameworkCore
If we want to do unit testing using the context class itself, we can use Moq.EntityFrameworkCore also. But it requires EF Core 6.
Install-Package Moq.EntityFrameworkCore
Limitations
Truncate
or Delete
SQL statements execute immediately, regardless of whether or not we call Db.SaveChanges()
Clear
is slower than Truncate
/Delete
and not good for large datasets. Clear
is suitable for regular unit testing, Truncate
and Delete
are not.
References
About Code Sample
- Visual Studio 2022 Solution
- ASP.NET 6
- EF Core 6, also tested in core 5
Database.Test
is an intrigued unit test project. Change the connection string in appsettings.json. Create Users table in db, check db.sql of project Database.Application
. Check/Run tests of EfCleanHelperTests.cs and EfCleanHelperUnitTests.cs.
{
"ConnectionStrings": {
"DatabaseConnection": "Data Source=.\\SQLEXPRESS;
Initial Catalog=Cup;Integrated Security=True"
}
}
DROP TABLE IF EXISTS [dbo].[Users]
GO
CREATE TABLE [dbo].[Users](
[Id] [bigint] IDENTITY(1,1) NOT NULL,
[Name] [nvarchar](max) NULL,
[Email] [nvarchar](max) NULL,
[IsDeleted] [bit] NOT NULL,
[CreatedOn] [datetime2](7) NOT NULL,
[CreatedBy] [nvarchar](max) NOT NULL,
[ModifiedOn] [datetime2](7) NULL,
[ModifiedBy] [nvarchar](max) NULL
)
History
- 15th August, 2022: Initial version
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