datagridview绑定到不更新数据库的实体

Question

I am populating a grid from a entity object and it is displaying the data fine. When I make changes and save it back, nothing is updating.

Here is my code:

In my load event:

  var query = from c in _entities.PaymentTypes
              where c.CorporationId == _currentcorp.CorporationId
              select
                new DataBindingProjection
                  {
                    PaymentTypeId = c.PaymentTypeId,
                    CorporationId = c.CorporationId,
                    TokenId = c.TokenId,
                    IsActive = c.IsActive,
                    Description = c.Description,
                    CashChargeCodeType = c.CashChargeCodeType,
                    SortOrder = c.SortOrder,
                    ExcludeCreditCode = c.ExcludeCreditCodes,
                    IsUpdated = c.IsUpdated,
                    IsAdded = c.IsAdded,
                    ClearUpdatedAndAdded = c.ClearUpdateAndAdded
                  };
  dataGridView_PaymentTypes.DataSource = query.ToList();

My class:

private class DataBindingProjection
{
  public Guid PaymentTypeId { get; set; }
  public Guid CorporationId { get; set; }
  public Guid TokenId { get; set; }
  public bool IsActive { get; set; }
  public string Description { get; set; }
  public int CashChargeCodeType { get; set; }
  public int SortOrder { get; set; }
  public int ExcludeCreditCode { get; set; }
  public bool IsUpdated { get; set; }
  public bool IsAdded { get; set; }
  public bool ClearUpdatedAndAdded { get; set; }
}

In the button to save the changes:

private void button_SaveChanges2_Click(object sender, EventArgs e)
{
  button_SaveChanges2.Enabled = false;
  _entities.SaveChanges();
  timer1.Enabled = true;
  button_SaveChanges2.Enabled = true;
}

What am I doing wrong?

In response to bmused:

Defined at the class level:

private SuburbanPortalEntities _entities;

defined in my load:

  var bs = new BindingSource();
  _entities.PaymentTypes.Where(x => x.CorporationId == _currentcorp.CorporationId).Load;
  bs.DataSource = _entities.PaymentTypes.Local.ToBindingList();
  dataGridView_PaymentTypes.DataSource = bs;

It is showing that it cannot load symbol Load and Local:

Answer 1

Two-way databinding with Winforms and Entity Framework can be achieved by creating an IBindinglist from the DbContext Local ObservableCollection<T> and setting it as the DataSource of a BindingSource . Example:

private BindingSource bs = new BindingSource();
private MyDbContext context = new MyDbContext();

context.MyEntities.Where(x=>x.SomeProperty == 2).Load(); 
bs.DataSource = context.MyEntities.Local.ToBindingList(); 
myDataGridView.DataSource = bs;

Answer 2

You are change the properties of the projected copy of the entity, while entity itself stays unchanged. That is why save does not work - entity stays unchanged.

You need either bind entities itself as DataSource to grid, or update property of the corresponding entity when you updating property of projection instance.

Answer 3

.Load()和.Local将是可见的，当使用参考：

 using System.Data.Entity;

Answer 4

You are creating the new DataBindingProjection() so we are assuming this is a class that is controlled by your context right?

Assuming that, what i see that is missing in your code is for you to pass the new instance of DataBindingProjection to your DbContext(if using 4.2+ or to the ObjectContext if using older versions, i would recommend migrating to 5.0)

You need to Attach() the created entities to the context before calling the SaveChanges(), i don't see this in your code.

The is the way for you to create new records to the database. If you want to change records that are at the database, you should not use the Linq approach where you create a new object, you should call the object itself, so it can have the EF proxies and be tracked by the ChangeTracker of EF.

For me it seems that you have a new class that is not tracked by EF.....

If you did something like this, then it should work (im assuming a property named Projection to be in your entities, just for an example) :

var query = from c in _entities.PaymentTypes
         where c.CorporationId == _currentcorp.CorporationId 
         select c.Projection;

dataGridView_PaymentTypes.DataSource = query.ToList();

If you dont have that then you should do something like this:

var query = from c in _entities.PaymentTypes
         where c.CorporationId == _currentcorp.CorporationId 
         new DataBindingProjection
              {
                PaymentTypeId = c.PaymentTypeId,
                CorporationId = c.CorporationId,
                TokenId = c.TokenId,
                IsActive = c.IsActive,
                Description = c.Description,
                CashChargeCodeType = c.CashChargeCodeType,
                SortOrder = c.SortOrder,
                ExcludeCreditCode = c.ExcludeCreditCodes,
                IsUpdated = c.IsUpdated,
                IsAdded = c.IsAdded,
                ClearUpdatedAndAdded = c.ClearUpdateAndAdded
              };

foreach(var item in query)
    (DbContext)YourInstanceOfContext.Set<DataBindingProjection>().Add(item);

dataGridView_PaymentTypes.DataSource = query.ToList();

After this you will be able to save it to the database.

Answer 5

看一下我关于绑定datagridView的帖子，该方法非常有效并且非常有用： 将datagridview绑定到数据库实体的最佳方法