DataGridView AllowUserToAddRow property doesn't work

Question

I have a simple project with Entity Framework, I have a DataGridView in my Form and I set its AllowUserToAddRow property to true but still I can not add new rows into it.

And here is my code:

DBEntities context = new DBEntities();
private void Form1_Load(object sender, EventArgs e)
{
    var q = (from i in context.myTable
             select i).ToList();
    DataGridView.DataSource = q;
}

private void btnSave_Click(object sender, EventArgs e)
{
    context.SaveChanges();
    MessageBox.Show("saved successfully");
}

If I use a BindingSource control, it allow me to insert rows in DataGridView but with this approach after I call context.SaveChanges() nothing insert in my database file. So I thought maybe its relative to this problem that DataGridView with true AllowUserToAddRow property doesn't let me to insert row in DataGridView.

Answer 1

Your problem is that you call .ToList() and materialize your query - this appears to break the full databinding.

You should be able to simply have:

DBEntities context = new DBEntities();
private void Form1_Load(object sender, EventArgs e)
{
    var q = (from i in context.myTable
             select i);
    DataGridView.DataSource = q;
}

I tried this and it works fine for allowing new rows (you do need to have a primary key in your table but you should have that anyway).

---

Do Note: this behaviour has been intentionally broken in Entity Framework 4.1 - Webforms data binding with EF Code-First Linq query error

---

I say should in my answer because I'm actually a little surprised it is this easy. I recall it not working so nicely in earlier versions of Entity Framework and I haven't used 4.0 very much.

If the solution above doesn't work you may have to do this the hard way and add new objects yourself before saving:

First introduce a binding source and when you save do something like (with an imaginary entity of Customer in the example):

foreach (Customer customer in bs.List)
{         
    // In my db customerId was an identity column set as primary key
    if (customer.CustomerId == 0)
        context.Customers.AddObject(customer);
}
context.SaveChanges();

Answer 2

I have just painfully upgraded to EF 6 from 4 and I have a similar issue, the solution in EF6 is below and I have shown a where statement for further help.

DBEntities context = new DBEntities();
private void Form1_Load(object sender, EventArgs e)
{
  context.MyTable.Where(e => e.myField == 1).Load();

  BindingSource bs = new BindingSource();
  bs.DataSource = context.MyTable.Local.ToBindingList();
  myDatagridView.DataSource = bs;
}

You can now use context.SaveChanges(); to save the changes or inserts

Answer 3

I have had a similar issue with a custom database implementation of an Interbase dialect. The solution for me was similar to that of above:

var tableAList = _dbImplementation.SelectAll<TableA>().ToList();
var bindingSource = new BindingSource();
bindingSource.DataSource = typeof (TableA);
foreach (var tableA in tableAList)
{
    bindingSource.Add(tableA);
}
dataGridView.DataSource = bindingSource;

Helpful reference: A Detailed Data Binding Tutorial

Answer 4

If you are going to bind the dataGridView to a source, then the only appropriate way to insert a row is to add a row to the data structure your DataGridView is binded to.

Answer 5

For me the problem was that I had added two new DataGrids to my form that are bound through a BindingList - but forgot to make a class for them inheriting from INotifyPropertyChanged. I had something like this:

public BindingList<String> MyProperty { get; set; } = "";

But it should have been this:

public BindingList<TextAndOrder> MyProperty { get;
set; } = new BindingList<TextAndOrder>();

In order for BindlingList to work it must be bound to a class that inherits from INotifyPropertyChanged

Where TextAndOrder Class was:

public class TextAndOrder : INotifyPropertyChanged
{
    private String _text = "";
    private int _order = 0;

    public String Text 
    {   
        get
        {
            return _text;
        }
        
        set
        {
            if (_text != value)
            {
                _text = value;
                this.NotifyPropertyChanged("Text");
            }
        }
    }

    public int Order 
    {
        get
        {
            return _order;
        }

        set
        {
            if (_order != value)
            {
                _order = value;
                this.NotifyPropertyChanged("Order");
            }
        }
    }


    private void NotifyPropertyChanged(string propertyName)

    {
        if (PropertyChanged != null)
        {
            this.PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
        }

    }

    public event PropertyChangedEventHandler PropertyChanged;


}

My Binding in the MainForm.cs was like:

grid.DataSource = MayDataClass.MyProperty; 
grid.AllowUserToAddRows = true; 
grid.AllowUserToDeleteRows = true; 
grid.AllowUserToResizeRows = true; 
grid.AllowUserToResizeColumns = true;