how to set null value to datetimepicker and textbox fields to save data into EF

Question

Hi All.

In Save button event I have

private void SaveEmployee_Click(object sender, RoutedEventArgs e)
{
    var employee = new EmployeeDT();

    if (Validate == true)
    {
        employee.EmployeeId = Guid.NewGuid();
        employee.Name = NameTextBox.Text;
        employee.Department = DepartmentTextBox.Text;
        employee.IsActive = IsActiveCheckBox.IsChecked.HasValue ? IsActiveCheckBox.IsChecked.Value : false;
        employee.CreatedDate = DateTime.Now;
        employee.CreatedBy = CreatedByTextBox.Text;
        employee.UpdateDate = ???????
        employee.UpdateBy = ???????

    var ea = new EmployeeAdapter();
    ea.SaveEmployee(employee);
    }
    else
        errorMessage();
}

How assign to employee.UpdateDate and employee.UpdateBy null or DBNull value?

Thanks.

Answer 1

Hello,

Is there are reason you would set these values to null? It would seem prudent to override SaveChanges and set those values there.

Example done in a dbContext class.

public override int SaveChanges()
{
    ChangeTracker.DetectChanges();

    foreach (var entry in ChangeTracker.Entries())
    {

        if (entry.State == EntityState.Added || entry.State == EntityState.Modified)
        {
            entry.Property("LastUpdated").CurrentValue = DateTime.Now;
            entry.Property("LastUser").CurrentValue = Environment.UserName;

            if (entry.Entity is Contact1 && entry.State == EntityState.Added)
            {
                entry.Property("CreatedAt").CurrentValue = DateTime.Now;
                entry.Property("CreatedBy").CurrentValue = Environment.UserName;
            }
        }
        else if (entry.State == EntityState.Deleted)
        {
            // Change state to modified and set delete flag
            entry.State = EntityState.Modified;
            entry.Property("isDeleted").CurrentValue = true;
        }

    }

    return base.SaveChanges();
}

See more here on shadow properties. For EF-6 see the following post.

Bottom line is you should not be setting these properties to null but if you must see the following post.

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Answer 2

Hi zleug,

Thank you for posting here.

If you need to set it to null for some reason, you can also take a look at this document.

Nullable value types (C# reference)

  DateTime? datetime = null;

Best Regards，

Timon

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