NullReferenceException when delete last row in a datagrid

**Brian Delahunty** · Nov 17 '05, 07:36 AM

RE: NullReferenceEx ception when delete last row in a datagrid

Can you post your code please.

--
Brian Delahunty
Ireland

page not found

http://briandela.com/blog

INDA SouthEast - http://southeast.developers.ie/ - The .NET usergroup I
started in the southeast of Ireland.

"Ryan Liu" wrote:
[color=blue]
> Hi there,
>
> I got a NullReferenceEx ception when delete last row in a datagrid.
>
> I had hard time to solve since it does not occur in my own code.
>
> I put a datagrid in my inherited user control, then put this control on a
> form.
>
> I use DataAdaptor to fill the data table and update database.
>
> I have no problem to delete rows in datagrid, unless it is last row.
>
> If I do delete the last row, use Delete key on my keyboard, it throws
> following exception.
>
> Is this a known bug? Or can someone point out the clue I can look at? Since
> the delet is not handled by myself, I really don't know how to solve it.
>
> Thanks a lot!
> Ryan
>
> System.NullRefe renceException: Object reference not set to an instance of an
> object.
> at System.Windows. Forms.DataGrid. ResetSelection( )
> at System.Windows. Forms.DataGrid. ResetUIState()
> at System.Windows. Forms.DataGrid. SetDataGridRows (DataGridRow[] newRows,
> Int32 newRowsLength)
> at System.Windows. Forms.DataGrid. DeleteDataGridR ows(Int32 deletedRows)
> at System.Windows. Forms.DataGrid. DeleteRows(Data GridRow[] localGridRows)
> at System.Windows. Forms.DataGrid. ProcessGridKey( KeyEventArgs ke)
> at System.Windows. Forms.DataGrid. ProcessDialogKe y(Keys keyData)
> at System.Windows. Forms.Control.P rocessDialogKey (Keys keyData)
> at System.Windows. Forms.TextBoxBa se.ProcessDialo gKey(Keys keyData)
> at System.Windows. Forms.Control.P reProcessMessag e(Message& msg)
> at
> System.Windows. Forms.ThreadCon text.System.Win dows.Forms.Unsa feNativeMethods +IMsoComponent. FPreTranslateMe ssage(MSG&
> msg)
> at
> System.Windows. Forms.Component Manager.System. Windows.Forms.U nsafeNativeMeth ods+IMsoCompone ntManager.FPush MessageLoop(Int 32
> dwComponentID, Int32 reason, Int32 pvLoopData)
> at System.Windows. Forms.ThreadCon text.RunMessage LoopInner(Int32 reason,
> ApplicationCont ext context)
> at System.Windows. Forms.ThreadCon text.RunMessage Loop(Int32 reason,
> ApplicationCont ext context)
> at System.Windows. Forms.Applicati on.Run(Form mainForm)
>
>
>[/color]

**Ryan Liu** · Nov 17 '05, 07:50 AM

Re: NullReferenceEx ception when delete last row in a datagrid

Hi Brian,

Have you found any problem with my code? Do you need more source code from
me?

Thanks a lot!
Ryan

"Ryan Liu" <rliu@eSpaceSof t.com> Ð´ÈëÏûÏ¢ÐÂÎÅ:OG BijChoFHA.2904@ tk2msftngp13.ph x.gbl...[color=blue]
> Hi Brian,
>
> Thanks for your help. I tied to send email to you from 3 mail server but
> all failed. I have to post to this group again.
>
> Here are the files related.
>
> a.. SelfDefineAbnor malEndGridContr ol inherits RefeshDataGerid Control
> b.. RefeshDataGerid Control use SysUtil to read and upate database.
> c.. RefeshDataGerid Control is put on SystemManager form, and user can
> edit, delete data.
>
> All these files are attached. I will high light the codes here.
>
>
> a.. SysUtil.cs public static MySqlDataAdapte r
> BuildDbAdapterF orSelfDefindedA bnormalEnd(IDbC onnection conn){} return a
> adapter to read and write back to db.
>
> b.. SelfDefineAbnor malEndGridContr ol implements RefeshDataGerid Control's
> RefreshDataImp( ) function to read data from db.
>
> c.. SystemManager is the form user can interactive with. It has 3 tab
> pages and quite some code. But for our discussion, it is simple, just a
> selfDefineAbnor malEndGridContr ol1 on it, and when form is load,
> SelfDefineAbnor malEndGridContr ol UpdateDb() method is called.
>
> You see, when user press Delete key on keyboard, this is function of
> datagrid, not control by my code. And it throw an exception when the user
> delete the last row in datagrid.
>
> Thanks a lot for your help!
> Ryan
>
>
>
>
> "Brian Delahunty" <BrianDelahunty @discussions.mi crosoft.com> Ð´ÈëÏûÏ¢ÐÂÎÅ:89 4251E6-A2F7-41C5-8787-7080EE23881F@mi crosoft.com...[color=green]
>> Can you post your code please.
>>
>> --
>> Brian Delahunty
>> Ireland
>>
>> http://briandela.com/blog
>>
>> INDA SouthEast - http://southeast.developers.ie/ - The .NET usergroup I
>> started in the southeast of Ireland.
>>
>>
>> "Ryan Liu" wrote:
>>[color=darkred]
>>> Hi there,
>>>
>>> I got a NullReferenceEx ception when delete last row in a datagrid.
>>>
>>> I had hard time to solve since it does not occur in my own code.
>>>
>>> I put a datagrid in my inherited user control, then put this control on
>>> a
>>> form.
>>>
>>> I use DataAdaptor to fill the data table and update database.
>>>
>>> I have no problem to delete rows in datagrid, unless it is last row.
>>>
>>> If I do delete the last row, use Delete key on my keyboard, it throws
>>> following exception.
>>>
>>> Is this a known bug? Or can someone point out the clue I can look at?
>>> Since
>>> the delet is not handled by myself, I really don't know how to solve it.
>>>
>>> Thanks a lot!
>>> Ryan
>>>
>>> System.NullRefe renceException: Object reference not set to an instance
>>> of an
>>> object.
>>> at System.Windows. Forms.DataGrid. ResetSelection( )
>>> at System.Windows. Forms.DataGrid. ResetUIState()
>>> at System.Windows. Forms.DataGrid. SetDataGridRows (DataGridRow[]
>>> newRows,
>>> Int32 newRowsLength)
>>> at System.Windows. Forms.DataGrid. DeleteDataGridR ows(Int32
>>> deletedRows)
>>> at System.Windows. Forms.DataGrid. DeleteRows(Data GridRow[]
>>> localGridRows)
>>> at System.Windows. Forms.DataGrid. ProcessGridKey( KeyEventArgs ke)
>>> at System.Windows. Forms.DataGrid. ProcessDialogKe y(Keys keyData)
>>> at System.Windows. Forms.Control.P rocessDialogKey (Keys keyData)
>>> at System.Windows. Forms.TextBoxBa se.ProcessDialo gKey(Keys keyData)
>>> at System.Windows. Forms.Control.P reProcessMessag e(Message& msg)
>>> at
>>> System.Windows. Forms.ThreadCon text.System.Win dows.Forms.Unsa feNativeMethods +IMsoComponent. FPreTranslateMe ssage(MSG&
>>> msg)
>>> at
>>> System.Windows. Forms.Component Manager.System. Windows.Forms.U nsafeNativeMeth ods+IMsoCompone ntManager.FPush MessageLoop(Int 32
>>> dwComponentID, Int32 reason, Int32 pvLoopData)
>>> at System.Windows. Forms.ThreadCon text.RunMessage LoopInner(Int32
>>> reason,
>>> ApplicationCont ext context)
>>> at System.Windows. Forms.ThreadCon text.RunMessage Loop(Int32 reason,
>>> ApplicationCont ext context)
>>> at System.Windows. Forms.Applicati on.Run(Form mainForm)
>>>
>>>
>>>[/color][/color]
>
>
>[/color]

**Ryan Liu** · Nov 17 '05, 08:03 AM

Re: NullReferenceEx ception when delete last row in a datagrid

Proiblen solved, all because I add CurrentCellChan ged event, in which, I
select whole row. When I remove it, it is fine.

/// <summary>
/// automatically select whole row
/// make it protected so when the class who inherits it can remove it
by -=
/// this is necessary when child allow delete the last row
/// then this event itself will not fire exception, but it will cause
datagrid internal exception
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
protected void dataGrid_Curren tCellChanged(ob ject sender, EventArgs e)
{
if(this.dataGri d.CurrentRowInd ex != -1) //not empty table
{
this.dataGrid.S elect(this.data Grid.CurrentRow Index);
}
}

"Ryan Liu" <rliu@eSpaceSof t.com> Ð´ÈëÏûÏ¢ÐÂÎÅ:Oo 6xes5oFHA.1416@ TK2MSFTNGP09.ph x.gbl...[color=blue]
> Hi Brian,
>
> Have you found any problem with my code? Do you need more source code from
> me?
>
> Thanks a lot!
> Ryan
>
>
> "Ryan Liu" <rliu@eSpaceSof t.com> Ð´ÈëÏûÏ¢ÐÂÎÅ:OG BijChoFHA.2904@ tk2msftngp13.ph x.gbl...[color=green]
>> Hi Brian,
>>
>> Thanks for your help. I tied to send email to you from 3 mail server but
>> all failed. I have to post to this group again.
>>
>> Here are the files related.
>>
>> a.. SelfDefineAbnor malEndGridContr ol inherits RefeshDataGerid Control
>> b.. RefeshDataGerid Control use SysUtil to read and upate database.
>> c.. RefeshDataGerid Control is put on SystemManager form, and user can
>> edit, delete data.
>>
>> All these files are attached. I will high light the codes here.
>>
>>
>> a.. SysUtil.cs public static MySqlDataAdapte r
>> BuildDbAdapterF orSelfDefindedA bnormalEnd(IDbC onnection conn){} return a
>> adapter to read and write back to db.
>>
>> b.. SelfDefineAbnor malEndGridContr ol implements
>> RefeshDataGerid Control's RefreshDataImp( ) function to read data from db.
>>
>> c.. SystemManager is the form user can interactive with. It has 3 tab
>> pages and quite some code. But for our discussion, it is simple, just a
>> selfDefineAbnor malEndGridContr ol1 on it, and when form is load,
>> SelfDefineAbnor malEndGridContr ol UpdateDb() method is called.
>>
>> You see, when user press Delete key on keyboard, this is function of
>> datagrid, not control by my code. And it throw an exception when the user
>> delete the last row in datagrid.
>>
>> Thanks a lot for your help!
>> Ryan
>>
>>
>>
>>
>> "Brian Delahunty" <BrianDelahunty @discussions.mi crosoft.com> Ð´ÈëÏûÏ¢ÐÂÎÅ:89 4251E6-A2F7-41C5-8787-7080EE23881F@mi crosoft.com...[color=darkred]
>>> Can you post your code please.
>>>
>>> --
>>> Brian Delahunty
>>> Ireland
>>>
>>> http://briandela.com/blog
>>>
>>> INDA SouthEast - http://southeast.developers.ie/ - The .NET usergroup I
>>> started in the southeast of Ireland.
>>>
>>>
>>> "Ryan Liu" wrote:
>>>
>>>> Hi there,
>>>>
>>>> I got a NullReferenceEx ception when delete last row in a datagrid.
>>>>
>>>> I had hard time to solve since it does not occur in my own code.
>>>>
>>>> I put a datagrid in my inherited user control, then put this control on
>>>> a
>>>> form.
>>>>
>>>> I use DataAdaptor to fill the data table and update database.
>>>>
>>>> I have no problem to delete rows in datagrid, unless it is last row.
>>>>
>>>> If I do delete the last row, use Delete key on my keyboard, it throws
>>>> following exception.
>>>>
>>>> Is this a known bug? Or can someone point out the clue I can look at?
>>>> Since
>>>> the delet is not handled by myself, I really don't know how to solve
>>>> it.
>>>>
>>>> Thanks a lot!
>>>> Ryan
>>>>
>>>> System.NullRefe renceException: Object reference not set to an instance
>>>> of an
>>>> object.
>>>> at System.Windows. Forms.DataGrid. ResetSelection( )
>>>> at System.Windows. Forms.DataGrid. ResetUIState()
>>>> at System.Windows. Forms.DataGrid. SetDataGridRows (DataGridRow[]
>>>> newRows,
>>>> Int32 newRowsLength)
>>>> at System.Windows. Forms.DataGrid. DeleteDataGridR ows(Int32
>>>> deletedRows)
>>>> at System.Windows. Forms.DataGrid. DeleteRows(Data GridRow[]
>>>> localGridRows)
>>>> at System.Windows. Forms.DataGrid. ProcessGridKey( KeyEventArgs ke)
>>>> at System.Windows. Forms.DataGrid. ProcessDialogKe y(Keys keyData)
>>>> at System.Windows. Forms.Control.P rocessDialogKey (Keys keyData)
>>>> at System.Windows. Forms.TextBoxBa se.ProcessDialo gKey(Keys keyData)
>>>> at System.Windows. Forms.Control.P reProcessMessag e(Message& msg)
>>>> at
>>>> System.Windows. Forms.ThreadCon text.System.Win dows.Forms.Unsa feNativeMethods +IMsoComponent. FPreTranslateMe ssage(MSG&
>>>> msg)
>>>> at
>>>> System.Windows. Forms.Component Manager.System. Windows.Forms.U nsafeNativeMeth ods+IMsoCompone ntManager.FPush MessageLoop(Int 32
>>>> dwComponentID, Int32 reason, Int32 pvLoopData)
>>>> at System.Windows. Forms.ThreadCon text.RunMessage LoopInner(Int32
>>>> reason,
>>>> ApplicationCont ext context)
>>>> at System.Windows. Forms.ThreadCon text.RunMessage Loop(Int32 reason,
>>>> ApplicationCont ext context)
>>>> at System.Windows. Forms.Applicati on.Run(Form mainForm)
>>>>
>>>>
>>>>[/color]
>>
>>
>>[/color]
>
>[/color]

NullReferenceException when delete last row in a datagrid

NullReferenceException when delete last row in a datagrid

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