public RadForm1()
        {
            InitializeComponent();
            this.radGridView1.Columns.Add("TextColumn");
            this.radGridView1.AutoSizeColumnsMode = GridViewAutoSizeColumnsMode.Fill;

            for (int i = 0; i < 30; i++)
            {
                this.radGridView1.Rows.Add(Guid.NewGuid().ToString());
            }
            this.radGridView1.CellValidating += radGridView1_CellValidating;

            this.radGridView1.EditorManager.CloseEditorWhenValidationFails = false;
        }

        private void radGridView1_CellValidating(object sender, CellValidatingEventArgs e)
        {
            if (e.Value == null || e.Value == "")
            {
                e.Cancel = true;
                RadMessageBox.Show("Value can't be empty!");
            }
        }

        public class MyGrid : RadGridView
        {
            public override string ThemeClassName
            {
                get
                {
                    return typeof(RadGridView).FullName;
                }
            }

            protected override void OnMouseDown(MouseEventArgs e)
            {
                RadScrollBarElement scrollBarAtPoint = GetScrollbarElementAtPoint<RadScrollBarElement>(this.GridViewElement.ElementTree, e.Location) as RadScrollBarElement;
                GridViewEditManager editManager = this.EditorManager;
                if (scrollBarAtPoint != null && this.ActiveEditor != null && !editManager.CloseEditorWhenValidationFails)
                {
                    bool isClosed = editManager.CloseEditor();
                    if (!isClosed)
                    {
                        return;
                    }
                }
                base.OnMouseDown(e);
            }

            internal T GetScrollbarElementAtPoint<T>(RadElementTree componentTree, Point point) where T : RadElement
            {
                if (componentTree != null)
                {
                    RadElement elementUnderMouse = componentTree.GetElementAtPoint(point);

                    while (elementUnderMouse != null)
                    {
                        T item = elementUnderMouse as T;

                        if (item != null)
                        {
                            return item;
                        }

                        elementUnderMouse = elementUnderMouse.Parent;
                    }
                }

                return null;
            }
        }

    Private Sub RadButton2_Click(sender As Object, e As EventArgs) Handles RadButton2.Click
        Dim spreadExporter As GridViewSpreadExport = New GridViewSpreadExport(gvAssetSchedule)
        AddHandler spreadExporter.CellFormatting, AddressOf spreadExporter_CellFormatting
        Dim exportRenderer As New SpreadExportRenderer()
        spreadExporter.ExportVisualSettings = True
        Dim filename = "..\..\export" & DateTime.Now.ToLongTimeString().Replace(":", "_") & ".xlsx"
        spreadExporter.RunExport(filename, exportRenderer)
        Process.Start(filename)
    End Sub

    Private Sub spreadExporter_CellFormatting(sender As Object, e As Telerik.WinControls.Export.CellFormattingEventArgs)
        If e.GridCellInfo Is Nothing Then
            Dim selection As CellSelection = e.CellSelection
            Dim range As CellRange = selection.CellRanges(0)
            Dim val = selection.Worksheet.Cells(range.FromIndex.RowIndex, range.FromIndex.ColumnIndex).GetValue()
            Dim format As New CellValueFormat("@")
            selection.Worksheet.Cells(range.FromIndex.RowIndex, range.FromIndex.ColumnIndex).SetFormat(format)
            Dim dt As New DateTime(1900, 1, 1)
            Dim parsedDays = 0
            If Integer.TryParse(val.Value.RawValue, parsedDays) Then
                dt = dt.AddDays(parsedDays)
                selection.Worksheet.Cells(range.FromIndex.RowIndex, range.FromIndex.ColumnIndex).SetValue(dt.Year & "-" & MonthName(dt.Month))
            End If
        End If
    End Sub

        public RadForm1()
        {
            InitializeComponent();

            DataTable dt = new DataTable();
            dt.Columns.Add("Id");
            dt.Columns.Add("Name");
            for (int i = 0; i < 10; i++)
            {
                dt.Rows.Add(i, "Item" + i); 
            }
            this.radGridView1.DataSource = dt; 
            this.radGridView1.AutoSizeColumnsMode = GridViewAutoSizeColumnsMode.Fill; 
             
            this.radGridView1.CellValidating += radGridView1_CellValidating;
        }

        private void radGridView1_CellValidating(object sender, CellValidatingEventArgs e)
        {
            if (e.Column.Index == 0 && e.ActiveEditor != null && e.Value + "" == "1")
            { 
                e.Cancel = true;
                RadMessageBox.Show("IncorrectValue");
            }
        }

        public class CustomGridView : RadGridView
        {
            public override string ThemeClassName  
            { 
                get 
                { 
                    return typeof(RadGridView).FullName;  
                }
            }

            protected override void OnMouseDown(MouseEventArgs e)
            {
             RadScrollBarElement scrollbar=   this.GridViewElement.ElementTree.GetElementAtPoint ( e.Location) as RadScrollBarElement;
             if (scrollbar!=null && this.IsInEditMode)
             {
                    this.EditorManager.CloseEditorWhenValidationFails = false;
                    this.EditorManager.CloseEditor();
                    return;
             }
                base.OnMouseDown(e);
            }
        }

        public class CustomGrid : RadGridView
        {
            public override string ThemeClassName
            {
                get
                {
                    return typeof(RadGridView).FullName;
                }
            }
            protected override void OnMouseDown(MouseEventArgs e)
            {
                GridExpanderItem expander = this.ElementTree.GetElementAtPoint(e.Location) as GridExpanderItem;
                if (expander != null)
                {
                    flag = true;
                }
                base.OnMouseDown(e);
            }

            protected override void OnMouseUp(MouseEventArgs e)
            {
                base.OnMouseUp(e);
                flag = false;
            }

            bool flag = false;

            protected override void OnPageChanging(object sender, PageChangingEventArgs e)
            {
                if (flag)
                {
                    e.Cancel = true;
                }
                base.OnPageChanging(sender, e);

            }
        }

private void RadGridView1_CreateRow(object sender, GridViewCreateRowEventArgs e)
{
    if (e.RowInfo is GridViewDetailsRowInfo)
    {
        e.RowElement = new MyGridDetailViewRowElement();
    }
}

public class MyGridDetailViewRowElement : GridDetailViewRowElement
{
    protected override SizeF MeasureOverride(SizeF availableSize)
    {
        var baseSize =  base.MeasureOverride(availableSize);
        if(baseSize.Width == float.PositiveInfinity)
        {
            baseSize.Width = 800;
        }
        return baseSize;
    }
}

        public RadForm1()
        {
            InitializeComponent();
            DataTable dt = new DataTable();
            dt.Columns.Add("DateOnly", typeof(DateOnly));
            dt.Rows.Add(new DateOnly(2022,3,3));

            this.radGridView1.AutoGenerateColumns = false;
            GridViewDateTimeColumn dateColumn = new GridViewDateTimeColumn();
            dateColumn.FieldName = "DateOnly";
            this.radGridView1.Columns.Add(dateColumn);
            this.radGridView1.DataSource = dt;
            this.radGridView1.AutoSizeColumnsMode = GridViewAutoSizeColumnsMode.Fill;
        }

        public RadForm1()
        {
            InitializeComponent();
            DataTable dt = new DataTable();
            dt.Columns.Add("DateOnly", typeof(DateOnly));
            dt.Rows.Add(new DateOnly(2022,3,3));

            this.radGridView1.AutoGenerateColumns = false;
            GridViewDateTimeColumn dateColumn = new GridViewDateTimeColumn();
            dateColumn.DataType = typeof(DateTime);
            dateColumn.FieldName = "DateOnly";
            dateColumn.Format = DateTimePickerFormat.Custom;
            dateColumn.CustomFormat = "dd/MM/yyyy";
            dateColumn.FormatString = "{0:dd/MM/yyyy}";
            dateColumn.DataTypeConverter = new DateOnlyConverter();
            this.radGridView1.Columns.Add(dateColumn);
            this.radGridView1.DataSource = dt;
            this.radGridView1.AutoSizeColumnsMode = GridViewAutoSizeColumnsMode.Fill;
        }


        public class DateOnlyConverter : TypeConverter
        {
            public override bool CanConvertTo(ITypeDescriptorContext context, Type destinationType)
            { 
                return destinationType == typeof(DateTime);
            }
            public override object ConvertTo(ITypeDescriptorContext context, CultureInfo culture, object value, Type destinationType)
            { 
                if (value is DateOnly && destinationType == typeof(DateTime))
                {
                    DateOnly date = (DateOnly)value;
                    return new DateTime(date.Year, date.Month, date.Day);
                }
                
                return base.ConvertTo(context, culture, value, destinationType);
            }
            public override bool CanConvertFrom(ITypeDescriptorContext context, Type sourceType)
            { 
                return sourceType == typeof(DateTime) ;
            }
            public override object ConvertFrom(ITypeDescriptorContext context, CultureInfo culture, object value)
            { 
                if (value is DateTime)
                {
                    DateTime date = (DateTime)value;
                    return new DateOnly(date.Year, date.Month, date.Day);
                }
                
                return base.ConvertFrom(context, culture, value);
            }
        }

GridViewDataColumn column;

column.HeaderText = "Счет";

column.HeaderImage = ...; // some img

column.TextImageRelation = TextImageRelation.Overlay;

GridViewDataColumn column;

column.HeaderText = "";

column.HeaderImage = ...; // some img

column.TextImageRelation = TextImageRelation.Overlay;

            GridViewDateTimeColumn orderDate = this.radGridView1.Columns["OrderDate"] as GridViewDateTimeColumn;
            orderDate.Format = DateTimePickerFormat.Custom;
            orderDate.CustomFormat = "dd-MM-yyyy";
            orderDate.FormatString = "{0:dd-MM-yyyy}";


            GridViewDateTimeColumn shippedDate = this.radGridView1.Columns["ShippedDate"] as GridViewDateTimeColumn;
            shippedDate.Format = DateTimePickerFormat.Custom;
            shippedDate.CustomFormat = "dd-MM-yyyy";
            shippedDate.FormatString = "{0:dd-MM-yyyy}";

this.radGridView1.LoadLayout(@"..\..\..\Layout.xml");

<RadGridView Padding="0, 0, 0, 1" Cursor="Default" TabIndex="49">
<MasterTemplate EnableGrouping = "True" AllowEditRow="False" AllowDeleteRow="False" AllowAddNewRow="False" EnableFiltering="True" AutoExpandGroups="True">
<Columns>
<Telerik.WinControls.UI.GridViewTextBoxColumn Width="100" FieldName="JobID" Name="JobID" IsAutoGenerated="True" IsVisible="True" HeaderText="JobID" />
<Telerik.WinControls.UI.GridViewTextBoxColumn Width="100" FieldName="CustomerID" Name="CustomerID" IsAutoGenerated="True" IsVisible="True" HeaderText="CustomerID" />
<Telerik.WinControls.UI.GridViewTextBoxColumn Width="285" FieldName="StatusID" Name="StatusID" IsAutoGenerated="True" IsVisible="True" HeaderText="StatusID" />
<Telerik.WinControls.UI.GridViewTextBoxColumn Width="100" FieldName="UnitID" Name="UnitID" IsAutoGenerated="True" IsVisible="True" HeaderText="UnitID" />
<Telerik.WinControls.UI.GridViewTextBoxColumn Width="100" FieldName="OperatorID" Name="OperatorID" IsAutoGenerated="True" IsVisible="True" HeaderText="OperatorID" />
<Telerik.WinControls.UI.GridViewTextBoxColumn Width="100" FieldName="JobTypeID" Name="JobTypeID" IsAutoGenerated="True" IsVisible="True" HeaderText="JobTypeID" />
<Telerik.WinControls.UI.GridViewTextBoxColumn Width="100" FieldName="JobCatID" Name="JobCatID" IsAutoGenerated="True" IsVisible="True" HeaderText="JobCatID" />
<Telerik.WinControls.UI.GridViewDateTimeColumn Width="100" FieldName="StartTime" Name="StartTime" IsAutoGenerated="True" IsVisible="True" HeaderText="StartTime">
<FilterDescriptor xsi:type="Telerik.WinControls.Data.DateFilterDescriptor" Value="" IgnoreTimePart="False" PropertyName="StartTime" Operator="IsNotNull" IsFilterEditor="True" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" />
</Telerik.WinControls.UI.GridViewDateTimeColumn>
<Telerik.WinControls.UI.GridViewDateTimeColumn Width="100" FieldName="FinishTime" Name="FinishTime" IsAutoGenerated="True" IsVisible="True" HeaderText="FinishTime" />
<Telerik.WinControls.UI.GridViewDateTimeColumn Width="100" FieldName="CreateDate" Name="CreateDate" SortOrder="Descending" IsAutoGenerated="True" IsVisible="True" HeaderText="CreateDate" />
<Telerik.WinControls.UI.GridViewDateTimeColumn Width="100" FieldName="StatusJobDate" Name="StatusJobDate" IsAutoGenerated="True" IsVisible="True" HeaderText="StatusJobDate" />
<Telerik.WinControls.UI.GridViewTextBoxColumn Width="100" FieldName="UserID" Name="UserID" IsAutoGenerated="True" IsVisible="True" HeaderText="UserID" />
<Telerik.WinControls.UI.GridViewTextBoxColumn DataType="System.Guid" Width="100" FieldName="TableKey" Name="TableKey" IsAutoGenerated="True" IsVisible="False" HeaderText="TableKey" />
</Columns>
<FilterDescriptors>
<Telerik.WinControls.Data.DateFilterDescriptor Value="" IgnoreTimePart="False" PropertyName="StartTime" Operator="IsNotNull" IsFilterEditor="True" />
</FilterDescriptors>
<SortDescriptors>
<Telerik.WinControls.Data.SortDescriptor PropertyName="CreateDate" Direction="Descending" />
</SortDescriptors>
<ViewDefinition xsi:type="Telerik.WinControls.UI.TableViewDefinition" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" />
</MasterTemplate>
</RadGridView>

public class CustomGridView : RadGridView
{
    protected override GridViewLayoutSerializer CreateGridViewLayoutSerializer(Telerik.WinControls.XmlSerialization.ComponentXmlSerializationInfo info)
    {
        return new CustomGridViewLayoutSerializer(info);
    }
    public override string ThemeClassName
    {
        get
        {
            return typeof(RadGridView).FullName;
        }
    }
}

public class CustomGridViewLayoutSerializer : GridViewLayoutSerializer
{ 
    public CustomGridViewLayoutSerializer(ComponentXmlSerializationInfo componentSerializationInfo) : base(componentSerializationInfo)
    {
    }

    protected override bool ProcessReaderAttribute(System.Xml.XmlReader reader, object parentObject, object toRead, PropertyDescriptor property)
    {
        if (toRead is FilterDescriptor && reader.Value == string.Empty)
        {
            object val = reader.Value;
            if (property.ComponentType == typeof(DateFilterDescriptor))
            {
                val = null;
            }
            
            this.SetPropertyValue(property, toRead, val);
            return true;
        }

        return base.ProcessReaderAttribute(reader, parentObject, toRead, property);
    }
}