Re: Linq-SQL canonical editable datagridview sample code

[Andrus]

Marc,

>I don't know if there is an easier way, but how about:

Thank you very much. I have issue on implementing add row properly using
this.

User presses down arrow in last row in grid starting adding new row.
Then user changes its mind desiding that new row should not added and
presses up arrow.
DataGridView does not show this unfinished row anymore.

However entity remains in DataContext and is added to database on
SubmitChanges.
How to prevent this ghost entity addition ?

Andrus.

[Marc Gravell]

Probably you'd need to implement ICancelAddNew, but taking a peek,
BindingList<Tal ready does this, calling RemoveItem correctly...
hmmm... I'll investigate...

[Marc Gravell]

I've looked at this with LINQ-to-SQL, and I cannot reproduce the
issue; if I add and remove a row (in any combination of immediate and
delayed cancel), then no change is applied to the database.

So: are you using LINQ-to-SQL, or are you using DbLinq? If the latter,
then I suspect it has "issues" noticing this trivial change (trivial
meant in the literal sense - not intended to be patronising).

You might be able to write the list to track insertions itself, but
this should be the job of the data-context. Of course, if this
actually is LINQ-to-SQL, please let me know and I'll retry...

Marc

[Andrus]

Marc,

>Probably you'd need to implement ICancelAddNew, but taking a peek,
BindingList<Ta lready does this, calling RemoveItem correctly...

I observed the following:

1. Pressing down arrow in last line of DataGridView calls AddNewCore() which
adds new entity to
DataContext.

2. Pressing Up Arrow doest *not* call RemoveItem. So added fake entity will
me saved on SubmitChanges() .

I'm wondering how Linq-SQL performs this correctly since RemoveItem() is not
called.

I'm using DbLinq but this should not depend on Linq provider.

Andrus.

[Andrus]

Marc,

I've looked at this with LINQ-to-SQL, and I cannot reproduce the
issue; if I add and remove a row (in any combination of immediate and
delayed cancel), then no change is applied to the database.

I'm planning to fix this in the following way:

1. AddNewCode() assigns new entity to property only, will not add to
DataContext
2. Override ICancelAddNew EndNew() method and add new entity to DataContext
in this method.

Will this work OK ?

Andrus.

[Marc Gravell]

Probably - but you can't *fully* verify the cancel conditions (the
index etc) since they aren't available as protected... I added
Console.WriteLi ne to RemoveItem, and it seemed to be working fine...

Marc

[Andrus]

Marc,

Probably - but you can't *fully* verify the cancel conditions (the
index etc) since they aren't available as protected... I added
Console.WriteLi ne to RemoveItem, and it seemed to be working fine...

I found that this occurs only when I move up-down in my
CustomDataGridV iewComBobox column.

Down arrow in this column invokes AddNewCore().
Up arrow does *not* invoke RemoveItem.
Pressing down arrow again causes InvalidOperatio nException in
base.AddNewCore ()

It seems that my combobox column class blocks bindinglist RemoveItem call.
I checked my class overridden methods and it seems that I'm calling base
methods in most cases.
Which combobox columns method calls bindinglist RemoveItem() ?
I implemented combobox column using MSDN sample code.

Any idea how to debug / resolve this issue? Exception which I got is below.

Andrus.

System.InvalidO perationExcepti on was unhandled
Message="Operat ion is not valid due to the current state of the object."
Source="System. Windows.Forms"
StackTrace:
at
System.Windows. Forms.DataGridV iew.DataGridVie wDataConnection .ProcessListCha nged(ListChange dEventArgs
e)
at
System.Windows. Forms.DataGridV iew.DataGridVie wDataConnection .currencyManage r_ListChanged(O bject
sender, ListChangedEven tArgs e)
at
System.Windows. Forms.CurrencyM anager.OnListCh anged(ListChang edEventArgs e)
at System.Windows. Forms.CurrencyM anager.List_Lis tChanged(Object
sender, ListChangedEven tArgs e)
at
System.Componen tModel.BindingL ist`1.OnListCha nged(ListChange dEventArgs e)
at System.Componen tModel.BindingL ist`1.InsertIte m(Int32 index, T
item)
at System.Collecti ons.ObjectModel .Collection`1.A dd(T item)
at System.Componen tModel.BindingL ist`1.AddNewCor e()
at MyAppl.TableLis t`1.AddNewCore( ) in I:\MyAppl\Table List.cs:line 92
at
System.Componen tModel.BindingL ist`1.System.Co mponentModel.IB indingList.AddN ew()
at System.Windows. Forms.CurrencyM anager.AddNew()
at
System.Windows. Forms.DataGridV iew.DataGridVie wDataConnection .AddNew()
at
System.Windows. Forms.DataGridV iew.DataGridVie wDataConnection .OnNewRowNeeded ()
at System.Windows. Forms.DataGridV iew.OnRowEnter( DataGridViewCel l&
dataGridViewCel l, Int32 columnIndex, Int32 rowIndex, Boolean
canCreateNewRow , Boolean validationFailu reOccurred)
at System.Windows. Forms.DataGridV iew.SetCurrentC ellAddressCore( Int32
columnIndex, Int32 rowIndex, Boolean setAnchorCellAd dress, Boolean
validateCurrent Cell, Boolean throughMouseCli ck)
at System.Windows. Forms.DataGridV iew.ProcessDown KeyInternal(Key s
keyData, Boolean& moved)
at System.Windows. Forms.DataGridV iew.ProcessDown Key(Keys keyData)
at
System.Windows. Forms.DataGridV iew.ProcessData GridViewKey(Key EventArgs e)
at System.Windows. Forms.DataGridV iew.ProcessKeyP review(Message& m)
at System.Windows. Forms.Control.P rocessKeyPrevie w(Message& m)
at System.Windows. Forms.Control.P rocessKeyMessag e(Message& m)
at System.Windows. Forms.ComboBox. ChildWndProc(Me ssage& m)
at
System.Windows. Forms.ComboBox. ComboBoxChildNa tiveWindow.WndP roc(Message& m)
at System.Windows. Forms.NativeWin dow.DebuggableC allback(IntPtr hWnd,
Int32 msg, IntPtr wparam, IntPtr lparam)
at System.Windows. Forms.UnsafeNat iveMethods.Disp atchMessageW(MS G&
msg)
at
....

[Marc Gravell]

Sorry - I don't think I'm going to be able to debug that just from a
stacktrace, and I'm not in a desparate hurry to pick through your full
bespoke code... sorry again...

Marc

[Andrus]

Marc,

I discovered that this occurs when all following conditions are met:

1. DataGridView contains single row
2. DataGridViewCol umn column is DataGridViewCom boBoxColumn
3. EditMode is EditOnEnter

In this case pressing up arrow in new row does *not* call BindingList
RemoveItem() method.

Is this .NET bug ? Any idea how to fix it ?

Andrus.

[Andrus]

Following code reproduces DataGridView crash on edit.
Press down arrow, up arrow, down arrow. Exception occurs.

Any idea how to fix ?

Andrus.

using System;
using System.Windows. Forms;
using System.Componen tModel;

class Supplier {
public string Id { get; set; }
}

class Form1 : Form {
[STAThread]
static void Main() {
Application.Run (new Form1());
}

public Form1() {
DataGridView grid = new DataGridView();
// if this line is commented out, all is OK:
grid.EditMode = DataGridViewEdi tMode.EditOnEnt er;
ComboBoxColumn comboBoxColumn = new ComboBoxColumn( );
ComboBoxCell ComboBoxCell = new ComboBoxCell();
comboBoxColumn. CellTemplate = ComboBoxCell;
grid.Columns.Ad d(comboBoxColum n);
BindingList<Sup plierl = new BindingList<Sup plier>();
l.Add(new Supplier());
grid.DataSource = l;
Controls.Add(gr id);
}

class ComboBoxColumn : DataGridViewCom boBoxColumn { }

class ComboBoxCell : DataGridViewCom boBoxCell {
public override Type EditType {
get {
return typeof(ComboBox EditingControl) ;
}
}

}

class ComboBoxEditing Control : ComboBox, IDataGridViewEd itingControl {
protected int rowIndex;
protected DataGridView dataGridView;
protected bool valueChanged = false;

protected override void OnTextChanged(E ventArgs e) {
base.OnTextChan ged(e);
NotifyDataGridV iewOfValueChang e();
}

protected virtual void NotifyDataGridV iewOfValueChang e() {
valueChanged = true;
if (dataGridView != null) {
dataGridView.No tifyCurrentCell Dirty(true);
}
}

public Cursor EditingPanelCur sor {
get {
return Cursors.IBeam;
}
}

public DataGridView EditingControlD ataGridView {
get {
return dataGridView;
}
set {
dataGridView = value;
}
}

public object EditingControlF ormattedValue {
set {
if (value.ToString () != Text) {
Text = value.ToString( );
NotifyDataGridV iewOfValueChang e();
}
}

get {
return Text;
}
}

public object
GetEditingContr olFormattedValu e(DataGridViewD ataErrorContext s
context) {
return Text;
}

public void PrepareEditingC ontrolForEdit(b ool selectAll) { }

public bool RepositionEditi ngControlOnValu eChange {
get {
return false;
}
}

public int EditingControlR owIndex {
get {
return rowIndex;
}

set {
rowIndex = value;
}
}

public void ApplyCellStyleT oEditingControl (DataGridViewCe llStyle
dataGridViewCel lStyle) {
DropDownStyle = ComboBoxStyle.D ropDown;
}

public bool EditingControlW antsInputKey(Ke ys keyData, bool
dataGridViewWan tsInputKey) {
return !dataGridViewWa ntsInputKey;
}

public bool EditingControlV alueChanged {

get {
return valueChanged;
}
set {
valueChanged = value;
}
}
}
}