The GridViewCheckBoxColumn.EditMode property controls when the value of the editor will be submitted to the cell. By default, the value is OnValidate and the value will be submitted only when the current cell changes, the grid looses focus or the active editor is closed by pressing Enter. If you set the EditMode property to OnValueChange it will submit the value immediately after the editor value changes. Please refer to the attached gif files illustrating the difference between the two modes. To reproduce: if you set the GridViewCheckBoxColumn.EnableHeaderCheckBox property to true, the cell value is always submitted immediately after toggle/untoggle the checkbox without considering that EditMode.OnValidate is used.
How to reproduce:
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
GridViewDecimalColumn decimalColumn = new GridViewDecimalColumn();
decimalColumn.Name = "DecimalColumn";
decimalColumn.HeaderText = "DecimalColumn";
this.radGridView1.MasterTemplate.Columns.Add(decimalColumn);
GridViewTextBoxColumn textBoxColumn = new GridViewTextBoxColumn();
textBoxColumn.Name = "TextBoxColumn";
textBoxColumn.HeaderText = "TextBoxColumn";
this.radGridView1.MasterTemplate.Columns.Add(textBoxColumn);
GridViewDateTimeColumn dateTimeColumn = new GridViewDateTimeColumn();
dateTimeColumn.Name = "DateTimeColumn";
dateTimeColumn.HeaderText = "DateTimeColumn";
this.radGridView1.MasterTemplate.Columns.Add(dateTimeColumn);
}
}
Workaround: this.radGridView1.MasterView.TableAddNewRow.MinHeight = 30;
When the EnableHeaderCheckBox property is set to true, whenever the checkbox is clicked in the new row, a new row is actually added to the grid before any other modifications are made. This can be replicated in the attached sample project. Run it and click the checkbox in the new row several times. Multiple rows are added. Workaround: cancel the RadGridView.UserAddingRow until all the required fields are filled.
To reproduce:
public Form1()
{
InitializeComponent();
DataTable dt = new DataTable();
dt.Columns.Add("Id");
dt.Columns.Add("Name");
for (int i = 0; i < 1; i++)
{
dt.Rows.Add(i, "Item");
}
this.radGridView1.DataSource = dt;
this.radGridView1.SelectionMode = GridViewSelectionMode.FullRowSelect;
this.radGridView1.ClipboardCopyMode = Telerik.WinControls.UI.GridViewClipboardCopyMode.EnableAlwaysIncludeHeaderText;
this.radGridView1.MultiSelect = true;
}
private void button1_Click(object sender, EventArgs e)
{
this.radGridView1.SelectAll();
this.radGridView1.Copy();
}
If you click the button, you will notice that only one cell is copied. However, if you add 2 and more rows, the whole grid content will be copied to the clipboard.
Workaround: use the BeginRowCopy/EndRowCopy methods.
private void button1_Click(object sender, EventArgs e)
{
this.radGridView1.SelectAll();
this.radGridView1.MasterTemplate.BeginRowCopy();
this.radGridView1.Copy();
this.radGridView1.MasterTemplate.EndRowCopy();
}
To reproduce:
- Add several columns including combo-box columns to a grid.
- Add one row and upon a button click, change the data source of the combo column.
Workaround:
Seth the following field to null prior changing the data source:
GetType(GridViewComboBoxColumn).GetField("nullBoundItem", Reflection.BindingFlags.Instance Or Reflection.BindingFlags.NonPublic).SetValue(combo, Nothing)
combo.DataSource = dt
To reproduce: add a RadGridView and a RadButton on the form. Use the following code snippet:
public RadForm1()
{
InitializeComponent();
this.radGridView1.Columns.Add("Col1");
this.radGridView1.Columns.Add("Col2");
for (int i = 0; i < 5; i++)
{
this.radGridView1.Rows.Add(i, "Item" + i);
}
this.radGridView1.AutoSizeColumnsMode = Telerik.WinControls.UI.GridViewAutoSizeColumnsMode.Fill;
this.radGridView1.RowValidating += radGridView1_RowValidating;
this.radGridView1.UserAddingRow += radGridView1_UserAddingRow;
}
private void radGridView1_UserAddingRow(object sender, Telerik.WinControls.UI.GridViewRowCancelEventArgs e)
{
e.Cancel = true;
}
private void radGridView1_RowValidating(object sender, Telerik.WinControls.UI.RowValidatingEventArgs e)
{
if (e.Row.IsModified && e.Row is GridViewDataRowInfo)
{
e.Cancel = true;
}
}
private void radButton1_Click(object sender, EventArgs e)
{
RadMessageBox.Show("Clicked");
}
1. Select a data cell and activate the editor. Enter some new value and click the button. The Click event is fired.
2. Select the new row and activate the editor. Enter some value and click the button. The Click event is NOT fired.
Workaround: use the CellValidating event instead.
To reproduce:
Sub New()
InitializeComponent()
Dim dt1 As New DataTable
dt1.Columns.Add("Id", GetType(Integer))
dt1.Columns.Add("Name", GetType(String))
For index = 1 To 20
dt1.Rows.Add(index, "Parent" & index)
Next
Me.RadGridView1.MasterTemplate.DataSource = dt1
Me.RadGridView1.AutoSizeColumnsMode = GridViewAutoSizeColumnsMode.Fill
Dim dt2 As New DataTable
dt2.Columns.Add("Id", GetType(Integer))
dt2.Columns.Add("Name", GetType(String))
dt2.Columns.Add("ParentId", GetType(Integer))
Dim dt3 As New DataTable
dt3.Columns.Add("Id", GetType(Integer))
dt3.Columns.Add("Name", GetType(String))
dt3.Columns.Add("ParentId", GetType(Integer))
For index = 1 To 20
If index Mod 2 = 0 Then
dt2.Rows.Add(index, "Child1." & index, index)
If index Mod 4 = 0 Then
dt3.Rows.Add(index, "Child2." & index, index)
End If
ElseIf index Mod 3 = 0 Then
dt3.Rows.Add(index, "Child2." & index, index)
Else
dt3.Rows.Add(index, "Child2." & index, index)
End If
Next
Dim template As New GridViewTemplate()
template.DataSource = dt2
template.AutoSizeColumnsMode = GridViewAutoSizeColumnsMode.Fill
RadGridView1.MasterTemplate.Templates.Add(template)
Dim relation As New GridViewRelation(RadGridView1.MasterTemplate)
relation.ChildTemplate = template
relation.RelationName = "FirstChild"
relation.ParentColumnNames.Add("Id")
relation.ChildColumnNames.Add("ParentId")
RadGridView1.Relations.Add(relation)
Dim template2 As New GridViewTemplate()
template2.DataSource = dt3
template2.AutoSizeColumnsMode = GridViewAutoSizeColumnsMode.Fill
RadGridView1.MasterTemplate.Templates.Add(template2)
Dim relation2 As New GridViewRelation(RadGridView1.MasterTemplate)
relation2.ChildTemplate = template2
relation2.RelationName = "SecondChild"
relation2.ParentColumnNames.Add("Id")
relation2.ChildColumnNames.Add("ParentId")
RadGridView1.Relations.Add(relation2)
AddHandler Me.RadGridView1.ChildViewExpanding, AddressOf ChildViewExpanding
End Sub
Private Sub RadGridView1_ViewCellFormatting(sender As Object, e As Telerik.WinControls.UI.CellFormattingEventArgs) _
Handles RadGridView1.ViewCellFormatting
Dim cell As GridDetailViewCellElement = TryCast(e.CellElement, GridDetailViewCellElement)
Dim expanderCell As GridGroupExpanderCellElement = TryCast(e.CellElement, GridGroupExpanderCellElement)
If expanderCell IsNot Nothing AndAlso TypeOf e.CellElement.RowElement Is GridDataRowElement Then
Dim hierarchyRow As GridViewHierarchyRowInfo = DirectCast(expanderCell.RowInfo, GridViewHierarchyRowInfo)
If Not IsExpandable(hierarchyRow) Then
expanderCell.Expander.Visibility = Telerik.WinControls.ElementVisibility.Hidden
Else
expanderCell.Expander.Visibility = Telerik.WinControls.ElementVisibility.Visible
End If
ElseIf cell IsNot Nothing Then
Dim hierarchyRow As GridViewHierarchyRowInfo = DirectCast(DirectCast(cell.RowInfo, GridViewDetailsRowInfo).Owner, _
GridViewHierarchyRowInfo)
For i As Integer = 0 To cell.PageViewElement.Items.Count - 1
Dim item As RadPageViewItem = cell.PageViewElement.Items(i)
Dim viewInfo As GridViewInfo = hierarchyRow.Views(i)
item.Text = "Child Template " & i
If viewInfo.ChildRows.Count = 0 Then
If i = 0 AndAlso i < cell.PageViewElement.Items.Count - 1 Then
cell.PageViewElement.Items(i + 1).IsSelected = True
End If
item.Visibility = Telerik.WinControls.ElementVisibility.Hidden
Else
item.Visibility = Telerik.WinControls.ElementVisibility.Visible
End If
Next
End If
End Sub
Private Function IsExpandable(hierarchyRow As GridViewHierarchyRowInfo) As Boolean
For Each view As GridViewInfo In hierarchyRow.Views
If view.ChildRows.Count > 0 Then
Return True
End If
Next
Return False
End Function
Workaround:
AddHandler Me.RadGridView1.ChildViewExpanding, AddressOf RadGridView1_ChildViewExpanding
AddHandler Me.RadGridView1.MouseDown, AddressOf RadGridView_MouseDown
Private Sub RadGridView1_ChildViewExpanding(sender As Object, e As ChildViewExpandingEventArgs)
If lastClicked IsNot Nothing AndAlso e.ParentRow.Equals(lastClicked) Then
e.Cancel = False
Else
e.Cancel = True
End If
End Sub
Dim lastClicked As GridViewRowInfo
Private Sub RadGridView_MouseDown(sender As Object, e As MouseEventArgs)
Dim expander As GridExpanderItem = TryCast(Me.RadGridView1.ElementTree.GetElementAtPoint(e.Location), GridExpanderItem)
If expander IsNot Nothing Then
lastClicked = DirectCast(expander.Parent, GridGroupExpanderCellElement).RowInfo
End If
End Sub
To reproduce:
- Add GridViewTextBoxColumn and set the MaxLength property.
- Paste in data row while the is not in edit mode.
Workaround:
private void RadGridView1_Pasting(object sender, Telerik.WinControls.UI.GridViewClipboardEventArgs e)
{
if (radGridView1.CurrentColumn.Name == "column1")
{
GridViewTextBoxColumn col = new GridViewTextBoxColumn();
var lenght = col.MaxLength;
if (Clipboard.ContainsData(DataFormats.Text))
{
e.Cancel = true;
string data = Clipboard.GetData(DataFormats.Text).ToString();
radGridView1.CurrentCell.Value = data.Substring(0, lenght);
}
}
}
Steps to reproduce: 1. Add a CompositeFilterDescriptor programmatically as it is demonstrated in the following help article: http://docs.telerik.com/devtools/winforms/gridview/filtering/setting-filters-programmatically-(composite-descriptors) 2. Save the layout. 3. Load the layout. Workaround: specify the PropertyName property for the CompositeFilterDescriptor.
To reproduce:
Sub New()
InitializeComponent()
Dim dt As New DataTable
dt.Columns.Add("Id", GetType(Integer))
dt.Columns.Add("Name", GetType(String))
dt.Columns.Add("Description", GetType(String))
For index = 1 To 5
dt.Rows.Add(index, "Item" & index, "Description" & index)
Next
Me.RadGridView1.DataSource = dt
Me.RadGridView1.AutoSizeColumnsMode = Telerik.WinControls.UI.GridViewAutoSizeColumnsMode.Fill
AddHandler Me.RadGridView1.UserAddingRow, AddressOf UserAddingRow
End Sub
Private Sub UserAddingRow(sender As Object, e As Telerik.WinControls.UI.GridViewRowCancelEventArgs)
Me.RadGridView1.MasterView.TableAddNewRow.ErrorText = ""
If String.IsNullOrEmpty(e.Rows(0).Cells(0).Value) Then
e.Cancel = True
Me.RadGridView1.MasterView.TableAddNewRow.ErrorText = "Empty value is not allowed!"
End If
End Sub
1. Click the new row and enter a value in the last cell.
2. Click outside the new row, e.g. click on a data row. The UserAddingRow event is canceled and the new row remains current.
3. Click a data row again without any modification on the new row. The new row is not current anymore.
4. However, you perform step 1and 2 but instead of clicking a data row, the user clicks a header cell, the new row is not current from the first time. It is necessary to forbid the user to exit the new row until the validation passes or the new row is canceled by pressing Enter.
Workaround: use the CellValidating/RowValidating event for validating.
Consider the case where there are many child views and you want to export only the ones that actually contain data. Currently, you can either export only one view or all. One should be able to pass all the views in the ChildViewExporting event.
Workaround: create a custom GridDetailViewCellElement
Public Class Form1
Sub New()
InitializeComponent()
AddHandler dgvPatients.CreateCell, AddressOf dgvPatients_CreateCell
End Sub
Private Sub dgvPatients_CreateCell(sender As Object, e As GridViewCreateCellEventArgs)
If e.CellType = GetType(GridDetailViewCellElement) Then
e.CellElement = New MyGridDetailViewCellElement(e.Column, e.Row)
End If
End Sub
End Class
Public Class MyGridDetailViewCellElement
Inherits GridDetailViewCellElement
Sub New(column As GridViewColumn, rowElement As GridRowElement)
MyBase.New(column, rowElement)
End Sub
Public Overrides Sub UpdateTabItemsVisibility()
If Me.DetailsRow Is Nothing Then
Return
End If
MyBase.UpdateTabItemsVisibility()
End Sub
End Class
To reproduce:
GridViewTextBoxColumn textBoxColumn1 = new GridViewTextBoxColumn("Col 1");
textBoxColumn1.FieldName = "col1";
radGridView1.MasterTemplate.Columns.Add(textBoxColumn1);
GridViewTextBoxColumn textBoxColumn2 = new GridViewTextBoxColumn("Col 2");
textBoxColumn2.FieldName = "col2";
textBoxColumn2.FormatString = "{0:d}";
radGridView1.MasterTemplate.Columns.Add(textBoxColumn2);
radGridView1.AutoSizeColumnsMode = GridViewAutoSizeColumnsMode.Fill;
DataTable dt = new DataTable();
dt.Columns.Add("col1", typeof(string));
dt.Columns.Add("col2", typeof(DateTime));
for (int i = 0; i < 10; i++)
{
dt.Rows.Add("Item" + i, DateTime.Now.AddDays(i));
}
this.radGridView1.AutoGenerateColumns = false;
this.radGridView1.DataSource = dt;
Right click the row header cell and select Copy. The following exception occurs although we don't have a GridViewDateTimeColumn : System.InvalidCastException was unhandled
HResult=-2147467262
Message=Unable to cast object of type 'Telerik.WinControls.UI.GridViewTextBoxColumn' to type 'Telerik.WinControls.UI.GridViewDateTimeColumn'.
Source=Telerik.WinControls.GridView
StackTrace:
at Telerik.WinControls.UI.MasterGridViewTemplate.CopyRows(String format, Boolean cut, Boolean cutOperation, StringBuilder content)
at Telerik.WinControls.UI.MasterGridViewTemplate.ProcessContent(String format, Boolean cut, Boolean cutOperation)
at Telerik.WinControls.UI.MasterGridViewTemplate.CopyContent(Boolean cut)
at Telerik.WinControls.UI.MasterGridViewTemplate.Copy()
at Telerik.WinControls.UI.GridDataRowElement.copyItem_Click(Object sender, EventArgs e)
at Telerik.WinControls.RadElement.OnClick(EventArgs e)
at Telerik.WinControls.UI.RadButtonItem.OnClick(EventArgs e)
at Telerik.WinControls.UI.RadMenuItem.OnClick(EventArgs e)
at Telerik.WinControls.RadElement.DoClick(EventArgs e)
at Telerik.WinControls.RadElement.RaiseBubbleEvent(RadElement sender, RoutedEventArgs args)
at Telerik.WinControls.RadItem.RaiseBubbleEvent(RadElement sender, RoutedEventArgs args)
at Telerik.WinControls.RadElement.RaiseRoutedEvent(RadElement sender, RoutedEventArgs args)
at Telerik.WinControls.RadElement.RaiseBubbleEvent(RadElement sender, RoutedEventArgs args)
at Telerik.WinControls.RadItem.RaiseBubbleEvent(RadElement sender, RoutedEventArgs args)
at Telerik.WinControls.RadElement.RaiseRoutedEvent(RadElement sender, RoutedEventArgs args)
at Telerik.WinControls.RadElement.DoMouseUp(MouseEventArgs e)
at Telerik.WinControls.ComponentInputBehavior.OnMouseUp(MouseEventArgs e)
at Telerik.WinControls.RadControl.OnMouseUp(MouseEventArgs e)
at System.Windows.Forms.Control.WmMouseUp(Message& m, MouseButtons button, Int32 clicks)
at System.Windows.Forms.Control.WndProc(Message& m)
at System.Windows.Forms.ScrollableControl.WndProc(Message& m)
at Telerik.WinControls.RadControl.WndProc(Message& m)
at Telerik.WinControls.UI.RadPopupControlBase.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.DebuggableCallback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)
at System.Windows.Forms.UnsafeNativeMethods.DispatchMessageW(MSG& msg)
at System.Windows.Forms.Application.ComponentManager.System.Windows.Forms.UnsafeNativeMethods.IMsoComponentManager.FPushMessageLoop(IntPtr dwComponentID, Int32 reason, Int32 pvLoopData)
at System.Windows.Forms.Application.ThreadContext.RunMessageLoopInner(Int32 reason, ApplicationContext context)
at System.Windows.Forms.Application.ThreadContext.RunMessageLoop(Int32 reason, ApplicationContext context)
at System.Windows.Forms.Application.Run(Form mainForm)
at _1075342CopyText.Program.Main() in d:\Projects\1075342CopyText_Binding\Program.cs:line 17
at System.AppDomain._nExecuteAssembly(RuntimeAssembly assembly, String[] args)
at System.AppDomain.ExecuteAssembly(String assemblyFile, Evidence assemblySecurity, String[] args)
at Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssembly()
at System.Threading.ThreadHelper.ThreadStart_Context(Object state)
at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
at System.Threading.ThreadHelper.ThreadStart()
InnerException:
Workaround: use a GridViewDateTimeColumn
The problematic themes are:
Aqua
HighContrastBlack
VisualStudio2012Dark
VisualStudio2012Light
Windows8
How to reproduce:
private void RadForm1_Load(object sender, EventArgs e)
{
var theme = new Windows8Theme();
ThemeResolutionService.ApplicationThemeName = "Windows8";
GridViewTextBoxColumn textBoxColumn = new GridViewTextBoxColumn();
textBoxColumn.Name = "Test";
this.radGridView1.Columns.Add(textBoxColumn);
for (int i = 0; i < 100; i++)
{
this.radGridView1.Rows.AddNew();
}
}
Workaround:
private void RadForm1_Load(object sender, EventArgs e)
{
var theme = new Windows8Theme();
ThemeResolutionService.ApplicationThemeName = "Windows8";
GridViewTextBoxColumn textBoxColumn = new GridViewTextBoxColumn();
textBoxColumn.Name = "Test";
this.radGridView1.Columns.Add(textBoxColumn);
this.radGridView1.BeginUpdate();
for (int i = 0; i < 100; i++)
{
this.radGridView1.Rows.AddNew();
}
this.radGridView1.EndUpdate();
int lastRow = this.radGridView1.Rows.Count - 1;
this.radGridView1.Rows[lastRow].IsCurrent = true;
}
Please refer to the attached sample project and select a new value in the drop down.
Workaround: change the PageSize in the RadDropDownListElement.PopupClosed event:
public sealed class PageSizeDropdownHeaderCellElement : GridHeaderCellElement
{
public PageSizeDropdownHeaderCellElement(GridViewColumn col, GridRowElement row) : base(col, row)
{
TextAlignment = ContentAlignment.TopCenter;
Alignment = ContentAlignment.TopCenter;
}
private RadDropDownListElement _dropDownListElement;
protected override void CreateChildElements()
{
base.CreateChildElements();
_dropDownListElement = new RadDropDownListElement();
if (_dropDownListElement != null && _dropDownListElement.DataSource == null)
{
_dropDownListElement = new RadDropDownListElement();
_dropDownListElement.BindingContext = new BindingContext();
_dropDownListElement.DropDownStyle = Telerik.WinControls.RadDropDownStyle.DropDownList;
_dropDownListElement.Items.Clear();
_dropDownListElement.Items.Add(new RadListDataItem("10", 10) { Selected = true });
_dropDownListElement.Items.Add(new RadListDataItem("25", 25));
_dropDownListElement.Items.Add(new RadListDataItem("50", 50));
_dropDownListElement.Items.Add(new RadListDataItem("100", 100));
_dropDownListElement.Items.Add(new RadListDataItem("All", -1));
_dropDownListElement.Margin = new Padding(15, 0, 0, 0);
_dropDownListElement.StretchHorizontally = true;
_dropDownListElement.NotifyParentOnMouseInput = false;
_dropDownListElement.Popup.MouseClick += Popup_MouseClick;
_dropDownListElement.PopupClosed += _dropDownListElement_PopupClosed;
this.Children.Add(_dropDownListElement);
}
}
RadListVisualItem elementUnderMouse;
private void Popup_MouseClick(object sender, MouseEventArgs e)
{
elementUnderMouse = _dropDownListElement.Popup.ElementTree.GetElementAtPoint(e.Location) as RadListVisualItem;
}
private void _dropDownListElement_PopupClosed(object sender, RadPopupClosedEventArgs args)
{
if (elementUnderMouse == null)
{
return;
}
if (_dropDownListElement.SelectedIndex == -1)
return;
var pageSize = Convert.ToInt32(elementUnderMouse.Data.Value);
if (pageSize == -1)
{
pageSize = GridControl.RowCount;
}
else
{
pageSize = pageSize <= GridControl.RowCount ? pageSize : GridControl.RowCount;
}
this.RowInfo.Tag = pageSize;
GridControl.PageSize = pageSize;
elementUnderMouse = null;
}
protected override void SetContentCore(object value)
{
if (_dropDownListElement != null && this.RowInfo.Tag != null)
{
this._dropDownListElement.SelectedValue = (int)this.RowInfo.Tag;
}
}
public override bool IsCompatible(GridViewColumn data, object context)
{
return data is ActionColumn && context is GridTableHeaderRowElement;
}
protected override Type ThemeEffectiveType
{
get
{
return typeof(GridHeaderCellElement);
}
}
}
To reproduce:
- Subscribe to the CellClick event
- Click several times in the grid with the right mouse button.
- At some point, the CellClick event will be executed.
Workaround:
- Use the Click event:
private void RadGridView1_Click(object sender, EventArgs e)
{
var args = e as MouseEventArgs;
if (args.Button == MouseButtons.Left)
{
var clickedCell = radGridView1.ElementTree.GetElementAtPoint(args.Location) as GridDataCellElement;
if (clickedCell != null)
{
//add your code here
}
}
}
To reproduce: - Add one-to-many relations hierarchy 3 or more child templates. - Export the grid using GridViewSpreadExport - The child rows of the last parent row are missing. Workaround: Add an empty parent row at the end of the grid.
To reproduce: - Bind the grid to an object that contains enum property. - Save the layout - Restart the application and load the layout before setting the DataSource of the grid. Workaround: Load the layout after the DataSource is set.
Description: if you filter a text column with "Does not contains" operator, the produced FilterDescriptors.Expression is "ProductName NOT LIKE '%c%' OR ProductName IS NULL". However, if you try to programmatically add this expression to the RadGridView.FilterDescriptors.Expression property it doesn't filter the grid.
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
Me.ProductsTableAdapter.Fill(Me.NwindDataSet.Products)
Me.RadGridView1.EnableFiltering = True
End Sub
Private Sub RadButton1_Click(sender As Object, e As EventArgs) Handles RadButton1.Click
Me.RadGridView1.FilterDescriptors.Expression = "ProductName NOT LIKE '%c%' OR ProductName IS NULL"
End Sub
Workaround: don't set expression but add a FilterDescriptor: http://docs.telerik.com/devtools/winforms/gridview/filtering/setting-filters-programmatically-(simple-descriptors)
Dim filter1 As New FilterDescriptor()
filter1.[Operator] = FilterOperator.NotContains
filter1.Value = "c"
filter1.IsFilterEditor = True
filter1.PropertyName = "ProductName"
Me.RadGridView1.FilterDescriptors.Add(filter1)