Unhandled exception rendering component: Specified cast is not valid.

Error: System.ArgumentNullException: Value cannot be null. (Parameter 'nullableType')

<TelerikGrid Data="strategicLevelItems" SelectedItems="selectedStrategic" Width="100%" Height="500px"
                                 ScrollMode="GridScrollMode.Scrollable" SelectionMode="GridSelectionMode.Multiple"
                                 SelectedItemsChanged="@((IEnumerable<GetNavigationNodesModel> strategicItems) => OnStrategicSelectAsync(strategicItems))"
                                 FilterMode="GridFilterMode.FilterRow">
                        <GridColumns>
                            <GridCheckboxColumn SelectAll="true" Width="40px" OnCellRender="@GridHelpers.CenterAlign" />
                            <GridColumn Field="@(nameof(GetNavigationNodesModel.Name))" />
                        </GridColumns>
                    </TelerikGrid>

    private async Task OnStrategicSelectAsync(IEnumerable<GetNavigationNodesModel> selectedItems)
    {
        selectedStrategic = selectedItems;

        var state = tacticalGrid.GetState();

        var compositeFilter = new CompositeFilterDescriptor() { LogicalOperator = FilterCompositionLogicalOperator.Or };
        foreach (var item in selectedItems)
        {
            compositeFilter.FilterDescriptors.Add(new FilterDescriptor()
            {
                Member = "ParentId",
                Operator = FilterOperator.IsEqualTo,
                Value = item.Id
            });
        }

        state.FilterDescriptors.Clear();
        state.FilterDescriptors.Add(compositeFilter);

        await tacticalGrid.SetState(state);
    }

@inject IJSRuntime _js

@* Move JavaScript code to a separate JS file in production *@
<script suppress-error="BL9992">
    function uncheckGrid() {
        var checkboxes = document.querySelectorAll(".no-select .k-grid-checkbox");
        for (var i = 0; i < checkboxes.length; i++) {
            checkboxes[i].checked = false;
        }
    }
</script>

<style>
    .no-select {
        cursor: not-allowed;
    }

    .no-select .k-checkbox {
        pointer-events: none;
    }
</style>

<TelerikGrid Data=@GridData
             SelectionMode="@GridSelectionMode.Multiple"
             SelectedItemsChanged="@((IEnumerable<Employee> employeeList) => OnSelect(employeeList))"
             SelectedItems="@SelectedEmployees"
             Pageable="true"
             Height="400px">
    <GridColumns>
        <GridCheckboxColumn SelectAll="true" OnCellRender="@OnGridCellRender" />
        <GridColumn Field="@nameof(Employee.Name)" />
        <GridColumn Field="@nameof(Employee.Team)" />
        <GridColumn Field="@nameof(Employee.Active)" />
    </GridColumns>
</TelerikGrid>

@if (SelectedEmployees != null)
{
    <ul>
        @foreach (Employee employee in SelectedEmployees)
        {
            <li>
                @employee.Name
            </li>
        }
    </ul>
}

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

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

    private void OnGridCellRender(GridCellRenderEventArgs args)
    {
        var product = (Employee)args.Item;
        if (!product.Active)
        {
            args.Class = "no-select";
        }
    }

    protected void OnSelect(IEnumerable<Employee> newSelected)
    {
        var validItemsToSelect = newSelected.Where(x => x.Active);
        SelectedEmployees = validItemsToSelect;
        if (validItemsToSelect.Count() < newSelected.Count())
        {
            _js.InvokeVoidAsync("uncheckGrid");
        }
    }

    protected override void OnInitialized()
    {
        for (int i = 1; i <= 7; i++)
        {
            GridData.Add(new Employee()
            {
                EmployeeId = i,
                Name = $"Employee {i}",
                Team = $"Team {i % 3 + 1}",
                Active = i % 2 == 0
            });
        }
    }

    public class Employee
    {
        public int EmployeeId { get; set; }
        public string Name { get; set; } = string.Empty;
        public string Team { get; set; } = string.Empty;
        public bool Active { get; set; }
    }
}

    .k-grid .k-grouping-header {
        padding: 0;
        border-bottom-width: 0;
        gap: 0;
    }

        .k-grid .k-grouping-header::before {
            margin: 0;
        }

    .k-grid .k-grouping-header .k-grouping-drop-container {
        margin: 0;
    }

@using System.ComponentModel.DataAnnotations

@inject IJSRuntime js

<label><TelerikCheckBox @bind-Value="@EnableScrollWorkaround" /> Enable Workaround</label>

<TelerikGrid Data="@GridData"
             EditMode="@GridEditMode.Inline"
             OnAdd="@OnGridAdd"
             OnUpdate="@OnGridUpdate"
             OnCreate="@OnGridCreate"
             Width="700px"
             Height="400px"
             Class="grid-class">
    <GridToolBarTemplate>
        <GridCommandButton Command="Add">Add Item</GridCommandButton>
    </GridToolBarTemplate>
    <GridColumns>
        <GridColumn Field="@nameof(Product.Name)" Width="200px" Locked="true" />
        <GridColumn Field="@nameof(Product.Price)" Width="200px" />
        <GridColumn Field="@nameof(Product.Quantity)" Width="200px" />
        <GridCommandColumn Width="200px" Locked="true">
            <GridCommandButton Command="Edit">Edit</GridCommandButton>
            <GridCommandButton Command="Save" ShowInEdit="true">Save</GridCommandButton>
            <GridCommandButton Command="Cancel" ShowInEdit="true">Cancel</GridCommandButton>
        </GridCommandColumn>
    </GridColumns>
</TelerikGrid>

<script suppress-error="BL9992">

    function scrollGridToTop() {
        var gridContentArea = document.querySelector(".grid-class .k-grid-content");
        if (gridContentArea) {
            gridContentArea.scrollTop = 0;
        }
    }

</script>

@code {
    private bool EnableScrollWorkaround { get; set; } = true;

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

    private int LastId { get; set; }

    private async Task OnGridAdd(GridCommandEventArgs args)
    {
        if (EnableScrollWorkaround)
        {
            await js.InvokeVoidAsync("scrollGridToTop");
        }
    }

    private void OnGridUpdate(GridCommandEventArgs args)
    {
        var updatedItem = (Product)args.Item;
        var originalItemIndex = GridData.FindIndex(i => i.Id == updatedItem.Id);

        if (originalItemIndex != -1)
        {
            GridData[originalItemIndex] = updatedItem;
        }
    }

    private void OnGridCreate(GridCommandEventArgs args)
    {
        var createdItem = (Product)args.Item;

        createdItem.Id = ++LastId;

        GridData.Insert(0, createdItem);
    }

    protected override void OnInitialized()
    {
        for (int i = 1; i <= 30; i++)
        {
            GridData.Add(new Product()
            {
                Id = ++LastId,
                Name = $"Product {LastId}",
                Quantity = (short)Random.Shared.Next(0, 1000),
                StartDate = DateTime.Now.AddDays(-Random.Shared.Next(60, 1000)),
                IsActive = LastId % 4 > 0
            });
        }
    }

    public class Product
    {
        public int Id { get; set; }
        [Required]
        public string Name { get; set; } = string.Empty;
        public decimal Price { get; set; }
        public int Quantity { get; set; }
        public DateTime StartDate { get; set; }
        public bool IsActive { get; set; }
    }
}

 <script>
        function clickButton(selector) {
            var btn = document.querySelector(selector);
            if (btn && btn.click) {
                btn.click();
            }
        }
    </script>

@inject IJSRuntime _js

<style>
    /* hide the built-in button if you like */
    .myExcelExportButton {
        display:none;
    }
</style>

<button @onclick="@MyExternalExportTrigger">my external export button</button>

<TelerikGrid Data="@GridData" Pageable="true" Sortable="true" Resizable="true" Reorderable="true"
             FilterMode="@GridFilterMode.FilterRow" Groupable="true"
             Class="@GridClass">
    <GridToolBar>
        <GridCommandButton Class="@ExportBtnClass" Command="ExcelExport" Icon="@IconName.FileExcel">Export to Excel</GridCommandButton>
        <label><TelerikCheckBox @bind-Value="@ExportAllPages" />Export All Pages</label>
    </GridToolBar>
    <GridExport>
        <GridExcelExport FileName="telerik-grid-export" AllPages="@ExportAllPages" />
    </GridExport>

    <GridColumns>
        <GridColumn Field="@nameof(SampleData.ProductId)" Title="ID" Width="100px" />
        <GridColumn Field="@nameof(SampleData.ProductName)" Title="Product Name" Width="300px" />
        <GridColumn Field="@nameof(SampleData.UnitsInStock)" Title="In stock" Width="100px" />
        <GridColumn Field="@nameof(SampleData.Price)" Title="Unit Price" Width="200px" />
        <GridColumn Field="@nameof(SampleData.Discontinued)" Title="Discontinued" Width="100px" />
        <GridColumn Field="@nameof(SampleData.FirstReleaseDate)" Title="Release Date" Width="300px" />
    </GridColumns>
</TelerikGrid>

@code {
    // cascade through classes on the grid and/or on the built-in button to click it with JS
    // so that it can invoke the built-in export operations
    string GridClass { get; set; } = "MyGrid";
    string ExportBtnClass { get; set; } = "myExcelExportButton";
    async Task MyExternalExportTrigger()
    {
        var selector = $".{GridClass} .k-header .{ExportBtnClass}";
        await _js.InvokeVoidAsync("clickButton", selector);
    }



    List<SampleData> GridData { get; set; }
    bool ExportAllPages { get; set; }

    protected override void OnInitialized()
    {
        GridData = Enumerable.Range(1, 100).Select(x => new SampleData
        {
            ProductId = x,
            ProductName = $"Product {x}",
            UnitsInStock = x * 2,
            Price = 3.14159m * x,
            Discontinued = x % 4 == 0,
            FirstReleaseDate = DateTime.Now.AddDays(-x)
        }).ToList();
    }

    public class SampleData
    {
        public int ProductId { get; set; }
        public string ProductName { get; set; }
        public int UnitsInStock { get; set; }
        public decimal Price { get; set; }
        public bool Discontinued { get; set; }
        public DateTime FirstReleaseDate { get; set; }
    }
}