C# Removing bindinglist item object on datagridview causes Exception
-
30-06-2021 - |
Question
I am very new to C#
.
I need to be able to remove objects from my bindinglist
which is a data source for a datagridview
. When I remove the last item I get the following exception:
System.NullReferenceException: Object reference not set to an instance of an object.
at System.Windows.Forms.DataGridViewRow.BuildInheritedRowStyle(Int32 rowIndex,
DataGridViewCellStyle inheritedRowStyle)
at System.Windows.Forms.DataGridViewRow.Paint(Graphics graphics, Rectangle clipBounds,
Rectangle rowBounds, Int32 rowIndex, DataGridViewElementStates rowState, Boolean isFirstDisplayedRow, Boolean isLastVisibleRow)
at System.Windows.Forms.DataGridView.PaintRows(Graphics g, Rectangle boundingRect,
Rectangle clipRect, Boolean singleHorizontalBorderAdded)
at System.Windows.Forms.DataGridView.PaintGrid(Graphics g, Rectangle gridBounds,
Rectangle clipRect, Boolean singleVerticalBorderAdded, Boolean singleHorizontalBorderAdded)
at System.Windows.Forms.DataGridView.OnPaint(PaintEventArgs e)
at System.Windows.Forms.Control.PaintWithErrorHandling(PaintEventArgs e, Int16 layer, Boolean disposeEventArgs)
at System.Windows.Forms.Control.WmPaint(Message& m)
at System.Windows.Forms.Control.WndProc(Message& m)
at System.Windows.Forms.DataGridView.WndProc(Message& m)
at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m)
at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m)
at System.Windows.Forms.NativeWindow.Callback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)
Here's My Code for removing the object:
studies is the bindinglist of study objects.
private void removeComplete()
{
if (studies.Count == 0)
return;
// Create temp list of copleted studies
List<study> completedStudies = studies.Where(s => s.isComplete() == true).ToList();
if (studies.Count == 0)
{
// do nothing
}
else
{
// If I don't use this line, every row produces the same exception
studies.RaiseListChangedEvents = false;
foreach (study study in completedStudies)
{
try
{
studies.Remove(study);
}
catch (Exception ex)
{
MessageBox.Show(ex.Message);
}
break;
}
// Turn it back on after turning it off above
studies.RaiseListChangedEvents = true;
// This is the point where it fails
studies.ResetBindings();
}
}
From what I can see, the datagridview still seems to be attempting to add a row which has just been removed from the source. Which is really odd to me.
Please help!
Solution
Thanks to a comment on my original question and a bit more research, I have found it was because the removeComplete() method call needed to be on the UI thread. To do this I used BeginInvoke as shown below:
public delegate void processDelegate();
private void processCompleted(object sender, EventArgs e)
{
processDelegate simpleDelegate = new processDelegate(removeComplete);
BeginInvoke(simpleDelegate);
}
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