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Request a Feature Report a Bug
Declined
Last Updated: 22 Apr 2024 14:19 by ADMIN
Maura Regan
Created on: 04 Apr 2024 15:04
Category: UI for WinForms
Type: Bug Report
0
System.NullReferenceException with Telerik.WinControls.UI.RadGridView

 

I'm a Progress OpenEdge developer and found issue with RadGridView using it in a ABL application. I have been able to reproduce the issue outside of the OpenEdge environment, and have attached a project file.

 

To see the issue, run the app, and scroll down really quickly with scrollbar thumb to the bottom.

You will then get:

System.NullReferenceException
  HResult=0x80004003
  Message=Object reference not set to an instance of an object.
  Source=Telerik.WinControls.GridView
  StackTrace:
   at Telerik.WinControls.UI.ExpressionAccessor.EvaluateExpression(GridViewRowInfo row, GridViewColumn column)

                       

Call Stack when I'm in my project:

> WindowsFormsApp1_NetFramework.exe!Progress.Data.DataSource.FillCacheFromPVMSource(Progress.Data.CacheRow cacheRow, int rowIx) Line 579 C#
WindowsFormsApp1_NetFramework.exe!Progress.Data.DataSource.GetRowError(int rowIx) Line 651 C#
WindowsFormsApp1_NetFramework.exe!Progress.Data.DummyRow.Error.get() Line 1347 C#
Telerik.WinControls.GridView.dll!Telerik.WinControls.UI.GridViewRowInfo.ErrorText.get() Unknown
Telerik.WinControls.GridView.dll!Telerik.WinControls.UI.GridDataRowElement.UpdateInfo() Unknown
Telerik.WinControls.GridView.dll!Telerik.WinControls.UI.GridRowElement.Initialize(Telerik.WinControls.UI.GridViewRowInfo rowInfo) Unknown
Telerik.WinControls.GridView.dll!Telerik.WinControls.UI.GridRowElement.Attach(Telerik.WinControls.UI.GridViewRowInfo row, object context) Unknown
Telerik.WinControls.UI.dll!Telerik.WinControls.UI.BaseVirtualizedContainer<Telerik.WinControls.UI.GridViewRowInfo>.UpdateElement(int position, Telerik.WinControls.UI.GridViewRowInfo data) Unknown
Telerik.WinControls.GridView.dll!Telerik.WinControls.UI.ScrollableRowsContainerElement.UpdateElement(int position, Telerik.WinControls.UI.GridViewRowInfo data) Unknown
Telerik.WinControls.UI.dll!Telerik.WinControls.UI.BaseVirtualizedContainer<Telerik.WinControls.UI.GridViewRowInfo>.MeasureElements() Unknown
Telerik.WinControls.UI.dll!Telerik.WinControls.UI.BaseVirtualizedContainer<Telerik.WinControls.UI.GridViewRowInfo>.MeasureOverride(System.Drawing.SizeF availableSize) Unknown
Telerik.WinControls.GridView.dll!Telerik.WinControls.UI.ScrollableRowsContainerElement.MeasureOverride(System.Drawing.SizeF availableSize) Unknown
Telerik.WinControls.dll!Telerik.WinControls.RadElement.MeasureCore(System.Drawing.SizeF availableSize) Unknown
Telerik.WinControls.dll!Telerik.WinControls.RadElement.Measure(System.Drawing.SizeF availableSize) Unknown
Telerik.WinControls.dll!Telerik.WinControls.Layouts.ContextLayoutManager.UpdateLayout() Unknown
Telerik.WinControls.dll!Telerik.WinControls.Layouts.ContextLayoutManager.UpdateLayoutCallback(Telerik.WinControls.Layouts.ILayoutManager manager) Unknown
[Native to Managed Transition]
[Managed to Native Transition]
mscorlib.dll!System.Delegate.DynamicInvokeImpl(object[] args) Line 123 C#
System.Windows.Forms.dll!System.Windows.Forms.Control.InvokeMarshaledCallbackDo(System.Windows.Forms.Control.ThreadMethodEntry tme) Unknown
System.Windows.Forms.dll!System.Windows.Forms.Control.InvokeMarshaledCallbackHelper(object obj) Unknown
mscorlib.dll!System.Threading.ExecutionContext.RunInternal(System.Threading.ExecutionContext executionContext, System.Threading.ContextCallback callback, object state, bool preserveSyncCtx) Line 980 C#
mscorlib.dll!System.Threading.ExecutionContext.Run(System.Threading.ExecutionContext executionContext, System.Threading.ContextCallback callback, object state, bool preserveSyncCtx) Line 928 C#
mscorlib.dll!System.Threading.ExecutionContext.Run(System.Threading.ExecutionContext executionContext, System.Threading.ContextCallback callback, object state) Line 917 C#

 

                                                   

Once I relinguish control back to Telerik, I get:

System.NullReferenceException
  HResult=0x80004003
  Message=Object reference not set to an instance of an object.
  Source=Telerik.WinControls.GridView
  StackTrace:
   at Telerik.WinControls.UI.ExpressionAccessor.EvaluateExpression(GridViewRowInfo row, GridViewColumn column)


Telerik.WinControls.GridView.dll!Telerik.WinControls.UI.ExpressionAccessor.EvaluateExpression(Telerik.WinControls.UI.GridViewRowInfo row, Telerik.WinControls.UI.GridViewColumn column) Unknown
Telerik.WinControls.GridView.dll!Telerik.WinControls.UI.ExpressionAccessor.this[Telerik.WinControls.UI.GridViewRowInfo].get(Telerik.WinControls.UI.GridViewRowInfo row) Unknown
Telerik.WinControls.GridView.dll!Telerik.WinControls.UI.GridViewRowInfo.this[Telerik.WinControls.UI.GridViewColumn].get(Telerik.WinControls.UI.GridViewColumn column) Unknown
Telerik.WinControls.GridView.dll!Telerik.WinControls.UI.GridDataCellElement.Value.get() Unknown
Telerik.WinControls.GridView.dll!Telerik.WinControls.UI.GridCellElement.SetContent() Unknown
Telerik.WinControls.GridView.dll!Telerik.WinControls.UI.GridVirtualizedCellElement.Initialize(Telerik.WinControls.UI.GridViewColumn column, Telerik.WinControls.UI.GridRowElement row) Unknown
Telerik.WinControls.GridView.dll!Telerik.WinControls.UI.GridVirtualizedCellElement.Attach(Telerik.WinControls.UI.GridViewColumn data, object context) Unknown
Telerik.WinControls.UI.dll!Telerik.WinControls.UI.BaseVirtualizedContainer<Telerik.WinControls.UI.GridViewColumn>.InsertElement(int position, Telerik.WinControls.UI.IVirtualizedElement<Telerik.WinControls.UI.GridViewColumn> element, Telerik.WinControls.UI.GridViewColumn data) Unknown
Telerik.WinControls.UI.dll!Telerik.WinControls.UI.BaseVirtualizedContainer<Telerik.WinControls.UI.GridViewColumn>.UpdateElement(int position, Telerik.WinControls.UI.GridViewColumn data) Unknown
Telerik.WinControls.UI.dll!Telerik.WinControls.UI.BaseVirtualizedContainer<Telerik.WinControls.UI.GridViewColumn>.MeasureElements() Unknown
Telerik.WinControls.UI.dll!Telerik.WinControls.UI.BaseVirtualizedContainer<Telerik.WinControls.UI.GridViewColumn>.MeasureOverride(System.Drawing.SizeF availableSize) Unknown
Telerik.WinControls.dll!Telerik.WinControls.RadElement.MeasureCore(System.Drawing.SizeF availableSize) Unknown
Telerik.WinControls.dll!Telerik.WinControls.RadElement.Measure(System.Drawing.SizeF availableSize) Unknown
Telerik.WinControls.GridView.dll!Telerik.WinControls.UI.GridVirtualizedRowElement.MeasureElements(System.Drawing.SizeF availableSize, System.Drawing.SizeF clientSize, System.Windows.Forms.Padding borderThickness) Unknown
Telerik.WinControls.UI.dll!Telerik.WinControls.UI.LightVisualElement.MeasureOverride(System.Drawing.SizeF availableSize) Unknown
Telerik.WinControls.GridView.dll!Telerik.WinControls.UI.GridRowElement.MeasureOverride(System.Drawing.SizeF availableSize) Unknown
Telerik.WinControls.dll!Telerik.WinControls.RadElement.MeasureCore(System.Drawing.SizeF availableSize) Unknown
Telerik.WinControls.dll!Telerik.WinControls.RadElement.Measure(System.Drawing.SizeF availableSize) Unknown
Telerik.WinControls.UI.dll!Telerik.WinControls.UI.VirtualizedStackContainer<Telerik.WinControls.UI.GridViewRowInfo>.MeasureElementCore(Telerik.WinControls.RadElement element, System.Drawing.SizeF availableSize) Unknown
Telerik.WinControls.GridView.dll!Telerik.WinControls.UI.ScrollableRowsContainerElement.MeasureElementCore(Telerik.WinControls.RadElement element, System.Drawing.SizeF availableSize) Unknown
Telerik.WinControls.UI.dll!Telerik.WinControls.UI.VirtualizedStackContainer<Telerik.WinControls.UI.GridViewRowInfo>.MeasureElement(Telerik.WinControls.UI.IVirtualizedElement<Telerik.WinControls.UI.GridViewRowInfo> element) Unknown
Telerik.WinControls.UI.dll!Telerik.WinControls.UI.BaseVirtualizedContainer<Telerik.WinControls.UI.GridViewRowInfo>.MeasureElements() Unknown
Telerik.WinControls.UI.dll!Telerik.WinControls.UI.BaseVirtualizedContainer<Telerik.WinControls.UI.GridViewRowInfo>.MeasureOverride(System.Drawing.SizeF availableSize) Unknown
Telerik.WinControls.GridView.dll!Telerik.WinControls.UI.ScrollableRowsContainerElement.MeasureOverride(System.Drawing.SizeF availableSize) Unknown
Telerik.WinControls.dll!Telerik.WinControls.RadElement.MeasureCore(System.Drawing.SizeF availableSize) Unknown
Telerik.WinControls.dll!Telerik.WinControls.RadElement.Measure(System.Drawing.SizeF availableSize) Unknown
Telerik.WinControls.dll!Telerik.WinControls.Layouts.ContextLayoutManager.UpdateLayout() Unknown
Telerik.WinControls.dll!Telerik.WinControls.Layouts.ContextLayoutManager.UpdateLayoutCallback(Telerik.WinControls.Layouts.ILayoutManager manager) Unknown
[Native to Managed Transition]
[Managed to Native Transition]
mscorlib.dll!System.Delegate.DynamicInvokeImpl(object[] args) Line 123 C#
System.Windows.Forms.dll!System.Windows.Forms.Control.InvokeMarshaledCallbackDo(System.Windows.Forms.Control.ThreadMethodEntry tme) Unknown
System.Windows.Forms.dll!System.Windows.Forms.Control.InvokeMarshaledCallbackHelper(object obj) Unknown
mscorlib.dll!System.Threading.ExecutionContext.RunInternal(System.Threading.ExecutionContext executionContext, System.Threading.ContextCallback callback, object state, bool preserveSyncCtx) Line 980 C#
mscorlib.dll!System.Threading.ExecutionContext.Run(System.Threading.ExecutionContext executionContext, System.Threading.ContextCallback callback, object state, bool preserveSyncCtx) Line 928 C#
mscorlib.dll!System.Threading.ExecutionContext.Run(System.Threading.ExecutionContext executionContext, System.Threading.ContextCallback callback, object state) Line 917 C#
System.Windows.Forms.dll!System.Windows.Forms.Control.InvokeMarshaledCallback(System.Windows.Forms.Control.ThreadMethodEntry tme) Unknown
System.Windows.Forms.dll!System.Windows.Forms.Control.InvokeMarshaledCallbacks() Unknown
System.Windows.Forms.dll!System.Windows.Forms.Control.WndProc(ref System.Windows.Forms.Message m) Unknown
System.Windows.Forms.dll!System.Windows.Forms.ScrollableControl.WndProc(ref System.Windows.Forms.Message m) Unknown
Telerik.WinControls.dll!Telerik.WinControls.RadControl.WndProc(ref System.Windows.Forms.Message m) Unknown
Telerik.WinControls.GridView.dll!Telerik.WinControls.UI.RadGridView.WndProc(ref System.Windows.Forms.Message m) Unknown
System.Windows.Forms.dll!System.Windows.Forms.Control.ControlNativeWindow.OnMessage(ref System.Windows.Forms.Message m) Unknown
System.Windows.Forms.dll!System.Windows.Forms.Control.ControlNativeWindow.WndProc(ref System.Windows.Forms.Message m) Unknown
System.Windows.Forms.dll!System.Windows.Forms.NativeWindow.DebuggableCallback(System.IntPtr hWnd, int msg, System.IntPtr wparam, System.IntPtr lparam) Unknown
[Native to Managed Transition]
[Managed to Native Transition]
System.Windows.Forms.dll!System.Windows.Forms.Application.ComponentManager.System.Windows.Forms.UnsafeNativeMethods.IMsoComponentManager.FPushMessageLoop(System.IntPtr dwComponentID, int reason, int pvLoopData) Unknown
System.Windows.Forms.dll!System.Windows.Forms.Application.ThreadContext.RunMessageLoopInner(int reason, System.Windows.Forms.ApplicationContext context) Unknown
System.Windows.Forms.dll!System.Windows.Forms.Application.ThreadContext.RunMessageLoop(int reason, System.Windows.Forms.ApplicationContext context) Unknown
System.Windows.Forms.dll!System.Windows.Forms.Application.Run(System.Windows.Forms.Form mainForm) Unknown
> WindowsFormsApp1_NetFramework.exe!WindowsFormsApp1_NetFramework.Program.Main() Line 19 C#

 

/////////////////////////////////////////////////////////////////////////////////////////////////

The following notes will explain what we are doing, since it may not be typical.

 

The MaxDataGuess functionality offers a time-saving alternative for the OpenEdge BindingSource that binds to a query with 
a very large result set. 
Some .NET controls must know the number of records in the result set when they initialize. 
By default, the ProBindingSource counts the records by reading the records in the query's result set, which can be time-consuming for large 
result sets. Setting this property provides the .NET control with an estimated value to bypass the counting process.
Sometimes, the result list can contain tens of thousands records, so this functionality would be used for that use case.


The project that demonstrates the issue found with the Telerik GridView is a much simpler version of the actual OpenEdge implementation.
The Progress.Data.DataSource._actualNumberOfRecords property is just a hard coded value that takes the place of the ABL query result set list,
since this project does not include the OpenEdge specific code.

The internal implementation of the MaxDataGuess in this project is as follows:

The DataSource.Count property is originally set to 50.
See Form1.cs:  pbs = new Progress.Data.BindingSource(myDataTable, maxDataGuess);


Once user scrolls through rows close to the Count property,  the routine CheckForOffEnd() is called 
(triggered by IDataErrorInfo.Error property).
If it determines that we are close to "current" end of rows, it adds 100 more rows calling
OnListChanged(new ListChangedEventArgs(ListChangedType.ItemAdded, ix));
to notify the grid control that we've update the Count property.

The routine FillCacheFromPVMSource() is called to fill in the CacheRow param for the specified rowIx.
The exception comes into play when the rowIx is greater than the current Count property.
If this is the case, then FillCacheFromPVMSource() updates the Count property, and also calls
OnListChanged(new ListChangedEventArgs(ListChangedType.ItemDeleted, ix));
when adjusting the Count property to notify the Telerik grid.

The exception occurs when control passes back to the Telerik code. 
The rowIx is no longer valid, and the Telerik grid does not check for this.


We get the following System.NullReferenceException:

'Object reference not set to an instance of an object.'

 

Attached Files:
2 comments
ADMIN
Dinko | Tech Support Engineer
Posted on: 22 Apr 2024 14:19

Hello Maura,

Thank you for being so patient.

After investigating the project and the DataSource class, the exception comes from calling the OnListChanged event too many times. This is not directly related to our RadGridView control. The event is called more times than the actual items in the row. When slowly scrolling the rows, the RadGridView validates the added rows and manages to handle this scenario. However, when you scroll very fast, the control cannot validate on time the rows that are added and the number of ListChanged event calls and throws an exception for an item that does not exist in the source. 

To handle this scenario, you will need to add an additional check in the CheckForOffEnd() method. 

internal void CheckForOffEnd(int rowIx)
{
   . . . . . .// your code
    if (rowIx == _count - 1 && _newIx == -1)
    {
       . . . . . .// your code
	   
        if (_pbs.Batching == true)
        {
           . . . . . .// your code

            if (rowsAdded > 0)
            {
                // We'll add the actual rows (DummyRow objects)
                // when the control asks for them.
                //_count += rowsAdded;
                totalCnt = _count + rowsAdded;
				
                if (totalCnt > this._actualNumberOfRecords)
                {
                    totalCnt = this._actualNumberOfRecords;
                }
				
                // Let the bound controls know of the change
                // OE00164955: Change from ItemAdded for each new row to Reset.
                // When combining batching/sorting, and sending these individually, they don't
                // get to grid in order we send them. Changing to Reset fixes problem.
                // OE00165534 Called Reset wasn't correct. It caused this regression.
                // Problem wasn't ItemAdded. It was the fact that _count was being set up front before
                // all calls to OnListChanged() were made. Incrementing _count as each call is done fixes both problems.
                //OnListChanged(new ListChangedEventArgs(ListChangedType.Reset, -1, -1));
                for (int ix = oldCnt; ix < totalCnt; ix++)
                {
                    _count++;
                    OnListChanged(new ListChangedEventArgs(ListChangedType.ItemAdded, ix));
                }
            }
        }
        // _bAccurateCount can only be set when _maxDataGuess is set and we haven't hit OffEnd
        else if (_pbs._bAccurateCount == false)
        {
            int totalCnt = _count + BindingSource.MAXDATAGUESS_INCR;

            if (totalCnt > this._actualNumberOfRecords)
            {
                totalCnt = this._actualNumberOfRecords;
            }

            for (int ix = oldCnt; ix < totalCnt; ix++)
            {
                _count++;
                OnListChanged(new ListChangedEventArgs(ListChangedType.ItemAdded, ix));
            }
        }
    }
    _inCheckForOffEnd = false;
}

I have added the check in both places. You could double-check if you need to add somewhere else in the custom class.

Regards,
Dinko | Tech Support Engineer
Progress Telerik

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ADMIN
Dinko | Tech Support Engineer
Posted on: 11 Apr 2024 11:02

Hi Maura Regan,

Thank you for the provided project and details. We were able to reproduce the exception in the project. However, we will need more time to investigate this exception and why the row is detached from its template. We will contact you again here as soon as we have more information. 

Regards,
Dinko | Tech Support Engineer
Progress Telerik

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