[Parameter]
public Action<GridCustomizeContextMenuEventArgs> CustomizeContextMenu { get; set; }

@inject NwindDataService NwindDataService

<DxGrid Data="Data"
        ShowGroupPanel="true"
        ContextMenus="@(GridContextMenus.Header)"
        CustomizeContextMenu="CustomizeContextMenu">
    <Columns>
        <DxGridSelectionColumn />
        <DxGridDataColumn FieldName="City" />
        <DxGridDataColumn FieldName="Country" />
        <DxGridDataColumn FieldName="CustomerName" GroupIndex="0" />
        <DxGridDataColumn FieldName="ProductName" />
        <DxGridDataColumn FieldName="Total"
                          UnboundType="GridUnboundColumnType.Decimal"
                          UnboundExpression="[UnitPrice] * [Quantity]"
                          DisplayFormat="c"
                          MinWidth="100" />
    </Columns>
</DxGrid>

@code {
    BindingList<Invoice> Data { get; set; }

    void CustomizeContextMenu(GridCustomizeContextMenuEventArgs args) {
        if (args.Context is GridHeaderCommandContext headerContext) {
            // Customizes context menu commands for the Total column header
            if (headerContext.Column is IGridDataColumn dataColumn && dataColumn.FieldName == "Total") {
                args.Items.Remove(GridContextMenuDefaultItemNames.GroupByColumn);
                args.Items.Remove(GridContextMenuDefaultItemNames.UngroupColumn);
            }
            // Customizes context menu commands for the selection column header
            if (headerContext.Column is IGridSelectionColumn selectionColumn) {
                var isFixed = selectionColumn.FixedPosition != GridColumnFixedPosition.None;
                string itemText = isFixed ? "Unfix Column" : "Fix Column to the Left";
                var newValue = isFixed ? GridColumnFixedPosition.None : GridColumnFixedPosition.Left;

                args.Items.AddCustomItem(itemText, () => {
                    headerContext.Grid.BeginUpdate();
                    headerContext.Column.FixedPosition = newValue;
                    headerContext.Grid.EndUpdate();
                });
            }
        }
    }

    protected override async Task OnInitializedAsync() {
        var invoices = await NwindDataService.GetInvoicesAsync();
        Data = new BindingList<Invoice>(invoices.ToList());
    }
}

public class Invoice {
    public string ShipName { get; set; }
    public string ShipAddress { get; set; }
    public string ShipCity { get; set; }
    public string ShipRegion { get; set; }
    public string ShipPostalCode { get; set; }
    public string ShipCountry { get; set; }
    public string CustomerId { get; set; }
    public string CustomerName { get; set; }
    public string Address { get; set; }
    public string City { get; set; }
    public string Region { get; set; }
    public string PostalCode { get; set; }
    public string Country { get; set; }
    public string Salesperson { get; set; }
    public int OrderId { get; set; }
    public DateTime? OrderDate { get; set; }
    public DateTime? RequiredDate { get; set; }
    public DateTime? ShippedDate { get; set; }
    public string ShipperName { get; set; }
    public int ProductId { get; set; }
    public string ProductName { get; set; }
    public decimal UnitPrice { get; set; }
    public short Quantity { get; set; }
    public float Discount { get; set; }
    public decimal? ExtendedPrice { get; set; }
    public decimal? Freight { get; set; }
}

public partial class NwindDataService {
    public Task<IEnumerable<Product>> GetProductsAsync(CancellationToken ct = default) {
        // Return your data here
    }
}

services.AddScoped<NwindDataService>();

void CustomizeContextMenu(GridCustomizeContextMenuEventArgs args) {    
    // Returns the first item
    IContextMenuItem firstItem = args.Items[0];
    // Returns the "Auto Fit All" item
    IContextMenuItem autoFitItem;
    if (args.Items.Contains(GridContextMenuDefaultItemNames.AutoFitAll))
        autoFitItem = args.Items[GridContextMenuDefaultItemNames.AutoFitAll];
}

void CustomizeContextMenu(GridCustomizeContextMenuEventArgs args) {  
      // Inserts the "Auto Fit All" item at the end of the item collection
      args.Items.Add(GridContextMenuDefaultItemNames.AutoFitAll);
      // Inserts the "Show Column Chooser" item at the first position in the item collection
      args.Items.Add(0, GridContextMenuDefaultItemNames.ShowColumnChooser);
}

void CustomizeContextMenu(GridCustomizeContextMenuEventArgs args) {
    // Inserts a custom item at the first position in the item collection
    var isFooterVisible = args.Grid.FooterDisplayMode != GridFooterDisplayMode.Never;
    string footerItemText = isFooterVisible ? "Hide Footer" : "Show Footer";
    var newState = isFooterVisible ? GridFooterDisplayMode.Never : GridFooterDisplayMode.Always;
    args.Items.AddCustomItem(0, footerItemText, () => {
        args.Grid.BeginUpdate();
        args.Grid.FooterDisplayMode = newState;
        args.Grid.EndUpdate();
    });
    // Inserts a custom item at the end of the item collection
    if (args.Context is GridHeaderCommandContext headerContext) {
        if (headerContext.Column is IGridCommandColumn commandColumn) {
            var isFixed = commandColumn.FixedPosition != GridColumnFixedPosition.None;
            string fixedItemText = isFixed ? "Unfix Column" : "Fix Column to the Left";
            var newValue = isFixed ? GridColumnFixedPosition.None : GridColumnFixedPosition.Left;
            args.Items.AddCustomItem(fixedItemText, () => {
                headerContext.Grid.BeginUpdate();
                headerContext.Column.FixedPosition = newValue;
                headerContext.Grid.EndUpdate();
            });
        }
    }
}

void CustomizeContextMenu(GridCustomizeContextMenuEventArgs args) {  
    if (args.Context is GridHeaderCommandContext headerContext) {
        // Inserts a custom item at the first position in the item collection
        var sortItem = args.Items.AddCustomItem(0, "Sort...");
        // Adds default items to the item collection of the inserted item
        sortItem.Items.Add(GridContextMenuDefaultItemNames.SortColumnAscending);
        sortItem.Items.Add(GridContextMenuDefaultItemNames.SortColumnDescending);
        sortItem.Items.Add(GridContextMenuDefaultItemNames.ClearColumnSorting);
    }
}

void CustomizeContextMenu(GridCustomizeContextMenuEventArgs args) {  
    // Removes the first item
    args.Items.Remove(0);
    // Removes the "Show Column Chooser" item
    args.Items.Remove(GridContextMenuDefaultItemNames.ShowColumnChooser);
    // Removes all items
    args.Items.Clear();
}

void CustomizeContextMenu(GridCustomizeContextMenuEventArgs args) {
    // Hides icons for all built-in commands
    foreach(var item in args.Items)
        item.IconUrl = string.Empty;   
    if (args.Context is GridHeaderCommandContext headerContext) {
        // Removes the "Sort Column Descending" item
        args.Items.Remove(GridContextMenuDefaultItemNames.SortColumnDescending);
        // Changes the "Sort Column Ascending" item caption
        args.Items[GridContextMenuDefaultItemNames.SortColumnAscending].Text = "Sort";
        // Adds and configures a custom command for the command column header
        if (headerContext.Column is IGridCommandColumn commandColumn) {
            var isFixed = commandColumn.FixedPosition != GridColumnFixedPosition.None;
            string itemText = isFixed ? "Unfix Column" : "Fix Column to the Left";
            var newValue = isFixed ? GridColumnFixedPosition.None : GridColumnFixedPosition.Left;

            var fixColumnItem = args.Items.AddCustomItem(itemText, () => {
                headerContext.Grid.BeginUpdate();
                headerContext.Column.FixedPosition = newValue;
                headerContext.Grid.EndUpdate();
            });
            fixColumnItem.BeginGroup = true;
        }
    }
}