@using Telerik.Blazor.Components.Grid

@inject IJSRuntime JS

<PageTitle>Home</PageTitle>

<TelerikGrid Data="@GridData">
    <GridToolBarTemplate>
        <TelerikButton OnClick="@ExportGridWithOtherColumns">Export Programmatically</TelerikButton>
        <GridCommandButton Class="hidden-export-button" Command="ExcelExport">Export Natively</GridCommandButton>
    </GridToolBarTemplate>
    <GridSettings>
        <GridExcelExport OnBeforeExport="@OnGridBeforeExport" />
    </GridSettings>
    <GridColumns>
        <GridColumn Field="@nameof(Product.Id)" Width="100px" />
        <GridColumn Field="@nameof(Product.Name)" Width="120px" />
        <GridColumn Title="Product Details">
            <Columns>
                <GridColumn Field="@nameof(Product.Group)" Width="180px" />
                <GridColumn Field="@nameof(Product.Price)" DisplayFormat="{0:c2}" Width="120px" />
                <GridColumn Field="@nameof(Product.Quantity)" DisplayFormat="{0:n0}" Width="120px" />
                <GridColumn Field="@nameof(Product.Released)" DisplayFormat="{0:d}" Width="180px" />
                <GridColumn Field="@nameof(Product.Discontinued)" Width="100px" />
            </Columns>
        </GridColumn>
    </GridColumns>
</TelerikGrid>

<style>
    .hidden-export-button {
        display: none;
    }
</style>

<script suppress-error="BL9992">
    function clickExportCommandButton() {
        let hiddenExportButton = document.querySelector(".hidden-export-button");
        if (hiddenExportButton) {
            hiddenExportButton.click();
        }
    }
</script>

@code {
    private List<Product> GridData { get; set; } = new();

    private void OnGridBeforeExport(GridBeforeExcelExportEventArgs args)
    {
        List<string> exportableColumnFields = new List<string> { nameof(Product.Name), nameof(Product.Price), nameof(Product.Quantity) };
        List<GridExcelExportColumn> ColumnsToExport = new();

        foreach (GridExcelExportColumn column in args.Columns)
        {
            if (exportableColumnFields.Contains(column.Field))
            {
                ColumnsToExport.Add(column);
            }
        }

        args.Columns = ColumnsToExport;
    }

    private async Task ExportGridWithOtherColumns()
    {
        await JS.InvokeVoidAsync("clickExportCommandButton");
    }

    protected override void OnInitialized()
    {
        var rnd = Random.Shared;

        for (int i = 1; i <= 7; i++)
        {
            GridData.Add(new Product()
            {
                Id = i,
                Name = $"Name {i} {(char)rnd.Next(65, 91)}{(char)rnd.Next(65, 91)}",
                Group = $"Group {i % 3 + 1}",
                Price = rnd.Next(1, 100) * 1.23m,
                Quantity = rnd.Next(0, 10000),
                Released = DateTime.Today.AddDays(-rnd.Next(60, 1000)),
                Discontinued = i % 4 == 0
            });
        }
    }

    public class Product
    {
        public int Id { get; set; }
        public string Name { get; set; } = string.Empty;
        public string Group { get; set; } = string.Empty;
        public decimal Price { get; set; }
        public int Quantity { get; set; }
        public DateTime Released { get; set; }
        public bool Discontinued { get; set; }
    }
}

<TelerikGrid Data="@GridData"
             SelectionMode="@GridSelectionMode.Multiple"
             SelectedItems="@SelectedItems"
             SelectedItemsChanged="@( (IEnumerable<Employee> newSelected) => OnSelectedItemsChanged(newSelected) )"
             Height="300px">
    <GridToolBarTemplate>
        <TelerikButton Enabled="@(SelectedItems.Any())" OnClick="@DeleteSelectedEmployees">Delete</TelerikButton>
    </GridToolBarTemplate>
    <GridColumns>
        <GridCheckboxColumn SelectAll="true" />
        <GridColumn Field="Name" Title="Name" />
        <GridColumn Field="Team" Title="Team" />
    </GridColumns>
</TelerikGrid>

@code {
    private List<Employee> GridData { get; set; } = Enumerable.Range(1, 10).Select(i => new Employee
    {
        EmployeeId = i,
        Name = $"Employee {i}",
        Team = $"Team {i % 3}"
    }).ToList();

    private List<Employee> SelectedItems { get; set; } = new();

    private void OnSelectedItemsChanged(IEnumerable<Employee> items)
    {
        SelectedItems = items.ToList();
    }

    private void DeleteSelectedEmployees()
    {
        if (SelectedItems.Any())
        {
            GridData = GridData.Except(SelectedItems).ToList();
            SelectedItems.Clear();
        }
    }

    public class Employee
    {
        public int EmployeeId { get; set; }
        public string Name { get; set; }
        public string Team { get; set; }
        public override bool Equals(object obj) => obj is Employee e && e.EmployeeId == EmployeeId;
        public override int GetHashCode() => EmployeeId.GetHashCode();
    }
}

private static void FlattenGroup<T>(AggregateFunctionsGroup group, List<T> result)
{
    if (group == null)
    {
        return;
    }

    if (group.HasSubgroups)
    {
        foreach (var sub in group.Items.OfType<AggregateFunctionsGroup>())
        {
            FlattenGroup(sub, result);
        }
    }
    else
    {
        result.AddRange(group.Items.OfType<T>());
    }
}

@page "/counter"
@using System.Collections.ObjectModel
General grid with its most common features
<TelerikGrid Data="@MyData" Pageable="true" @bind-Page="page" PageSize="5" TotalCount="30" OnRead="@ReadItems" >
    <GridColumns>
        <GridColumn Field="@(nameof(SampleData.Id))" Width="120px" />
        <GridColumn Field="@(nameof(SampleData.Name))" Title="Employee Name" Groupable="false" />
        <GridColumn Field="@(nameof(SampleData.Team))" Title="Team" />
        <GridColumn Field="@(nameof(SampleData.HireDate))" Title="Hire Date" />
    </GridColumns>
</TelerikGrid>

@code {
    public List<SampleData> MyData { get; set; } = new List<SampleData>();
    //public ObservableCollection<SampleData> MyData { get; set; } = new ObservableCollection<SampleData>();
    private int page = 1;

    private void ReadItems(GridReadEventArgs args)
    {
        //MyData = new List<SampleData>();  //OK!
        //MyData = new ObservableCollection<SampleData>(); //OK!
        MyData.Clear();  //List: No update. ObservableCollection: System.StackOverflowException!
        Populate();
        StateHasChanged();
    }

    private void Populate()
    {
        foreach (var data in Enumerable.Range((page - 1) * 5, 5).Select(x => new SampleData
        {
            Id = x,
            Name = "name " + x,
            Team = "team " + x % 5,
            HireDate = DateTime.Now.AddDays(-x).Date
        }))
        {
            MyData.Add(data);
        }
    }

    public class SampleData
    {
        public int Id { get; set; }
        public string Name { get; set; }
        public string Team { get; set; }
        public DateTime HireDate { get; set; }
    }
}