EF Core Delete

Summary: in this tutorial, you’ll learn how to delete data from the database tables in EF Core.

Setting up a sample project

First, download the HR sample project:

Second, run the Add-Migration command in the Package Manager Console (PMC) to create a new migration:

Add-Migration InitialCode language: C# (cs)

Third, execute the Update-Database command in the PMC to create a new HR database and tables in the local SQL Server:

Update-DatabaseCode language: C# (cs)

Perform a simple delete

We’ll work with Departments & Employees tables:

The following inserts a new department to the Departments table:

using HR;

using var context = new HRContext();

var department = new Department() { Name = "Logistics" };
context.Departments.Add(department);

context.SaveChanges();Code language: C# (cs)

The Departments table will contain a row with Id 1:

Id          Name
----------- ---------------
1           LogisticsCode language: plaintext (plaintext)

To delete a row from the database, you follow these steps:

First, get the entity from the database.
Second, remove the entity from the DbSet by calling DbSet‘s Remove() method.
Third, apply the change to the database by calling the SaveChanges() method.

For example, the following gets the department with Id 1 and removes it from the database:

using HR;

using var context = new HRContext();

// get the deparment
var department = context.Departments.Find(1);

if(department is not null)
{
    // remove it
    context.Departments.Remove(department);
    
    // commit the change to the database
    context.SaveChanges();
}Code language: C# (cs)

How it works.

First, get the department with id 1 from the database:

var department = context.Departments.Find(1);Code language: C# (cs)

EF Core executes a SELECT statement that retrieves a department by id:

-- [Parameters=[@__p_0='1'], CommandType='Text', CommandTimeout='30']
SELECT TOP(1) [d].[Id], [d].[Name]
FROM [Departments] AS [d]
WHERE [d].[Id] = @__p_0Code language: C# (cs)

Second, remove the department from the DbSet and call the SaveChanges() to remove the department from the database:

if(department is not null)
{
    // remove it
    context.Departments.Remove(department);
    
    // commit the change to the database
    context.SaveChanges();
}Code language: C# (cs)

EF Core will perform a simple DELETE statement that deletes the department with id 1 from the Departments table:

-- [Parameters=[@p0='1'], CommandType='Text', CommandTimeout='30']
SET IMPLICIT_TRANSACTIONS OFF;
SET NOCOUNT ON;
DELETE FROM [Departments]
OUTPUT 1
WHERE [Id] = @p0;Code language: SQL (Structured Query Language) (sql)

Cascade Delete

The following program inserts an employee with a department into the Employees and Departments tables:

using HR;

using var context = new HRContext();

var employee = new Employee()
{
    FirstName = "Jane",
    LastName = "Doe",
    Salary = 120_000,
    JoinedDate = new DateTime(2023, 5, 1),
    Department = new Department() { Name = "IT" }
};

context.Add(employee);
context.SaveChanges();Code language: C# (cs)

The Employees table (not all fields):

Id          FirstName       LastName        DepartmentId
----------- --------------- --------------- ------------
1           Jane            Doe             2Code language: plaintext (plaintext)

The Departments table:

Id          Name
----------- ---------------
2           ITCode language: plaintext (plaintext)

The DepartmentId column of the Employees table references the Id column of the Employees table. Due to the default foreign key constraint settings, when you delete a department, all employees that associate with the department will also be removed automatically by the database server. It’s called ON DELETE CASCADE in the database.

For example:

using HR;

using var context = new HRContext();

// find department id 2 
var department = context.Departments.Find(2);

if (department is not null)
{
    // delete the department
    context.Departments.Remove(department);
    context.SaveChanges();

    // all employees associcated with the department
    // will be removed by the database
}Code language: C# (cs)

If you view the data of the Departments and Employees tables, you’ll see that both tables are empty

Summary

To delete an entity, first, get it from the database, then remove it from the DbSet, and call the SaveChanges() to delete it from the database.

Was this tutorial helpful ?