<TelerikGrid FilterMode="Telerik.Blazor.GridFilterMode.FilterRow"
             Data="@GridData"
             Resizable="true">
    <DetailTemplate>
        detail template
    </DetailTemplate>
    <GridColumns>
        <GridColumn Field="Id" />
        <GridColumn Field="Id" Title="Resize Me First" />
        <GridColumn Field="Id" Title="Resize Me First" />
    </GridColumns>
</TelerikGrid>

@code {
    List<GridModel> GridData { get; set; }

    protected override void OnInitialized()
    {
        List<GridModel> data = new List<GridModel>();

        for (int i = 1; i <= 3; i++)
        {
            data.Add(new GridModel { Id = i });
        }

        GridData = data;
    }

    public class GridModel
    {
        public int Id { get; set; }
    }
}

@using Telerik.DataSource

<TelerikGrid Data=@GridData @ref="TheGrid"
             Groupable="true"
             OnStateInit="@((GridStateEventArgs<User> args) => OnStateInitHandler(args))">
    <GridColumns>
        <GridColumn Title="Personal Information">
            <Columns>
                <GridColumn Field=@nameof(User.LName) Title="Last Name" />
                <GridColumn Field=@nameof(User.FName) Title="First Name" />
            </Columns>
        </GridColumn>
        <GridColumn Title="Status and Last Login">
            <Columns>
                <GridColumn Field=@nameof(User.StatusName) Title="StatusName" />
                <GridColumn Field=@nameof(User.LastLoginDate) Title="Last Login" DisplayFormat="{0:yyyy-MMM-dd}" />
            </Columns>
        </GridColumn>
    </GridColumns>
</TelerikGrid>

@code {
    TelerikGrid<User> TheGrid { get; set; }
    List<User> GridData { get; set; }

    protected override void OnInitialized()
    {
        var data = new List<User>();
        for (int i = 1; i <= 20; i++)
        {
            data.Add(new User()
            {
                Id = i,
                FName = "First Name " + i,
                LName = "Last Name " + i,
                StatusId = i * 123,
                LastLoginDate = DateTime.Now,
                StatusName = "Status Name " + (i % 5 + 1)
            });
        }
        GridData = data;
    }

    private void OnStateInitHandler(GridStateEventArgs<User> args)
    {
        GridState<User> desiredState = new GridState<User>()
        {
            GroupDescriptors = new List<GroupDescriptor>()
            {
                new GroupDescriptor()
                {
                    Member = nameof(User.StatusName),
                    MemberType = typeof(string)
                }
            }
        };

        // will trigger an exception if grouping by a nested column
        args.GridState = desiredState;
    }

    @*protected override async Task OnAfterRenderAsync(bool firstRender)
    {
        if (firstRender)
        {
            var desiredState = TheGrid.GetState();

            desiredState.GroupDescriptors = new List<GroupDescriptor>()
            {
                new GroupDescriptor()
                {
                    Member = nameof(User.StatusName),
                    MemberType = typeof(string)
                }
            };

            await TheGrid.SetState(desiredState);
        }

        await base.OnAfterRenderAsync(firstRender);
    }*@

    public class User
    {
        public long Id { get; set; }

        public int StatusId { get; set; }
        public string StatusName { get; set; }

        public string FName { get; set; }
        public string LName { get; set; }

        public DateTime LastLoginDate { get; set; }
    }
}

Error: System.ArgumentException: Page Size cannot be less than one (Parameter 'PageSize') 

@using Telerik.DataSource.Extensions

@*  workaround:  *@

@*Page="@GridPage"
PageChanged="@OnGridPageChanged"*@

<TelerikGrid OnRead="@OnGridRead"
             Navigable="true"
             TItem="@Product"
             Pageable="true">
    <GridColumns>
        <GridColumn Field="@nameof(Product.Name)" Title="Product Name" />
    </GridColumns>
</TelerikGrid>

@code {
    List<Product> GridData { get; set; }
    int GridPage { get; set; } = 1;
    int GridTotal { get; set; }

    // workaround
    void OnGridPageChanged(int newPage)
    {
        if (newPage > 0 && newPage <= Math.Ceiling((double)GridTotal / (double)10))
        {
            GridPage = newPage;
        }
    }

    void OnGridRead(GridReadEventArgs args)
    {
        var result = GridData.ToDataSourceResult(args.Request);

        args.Data = result.Data;
        args.Total = result.Total;

        // workaround
        //GridTotal = result.Total;
    }

    protected override void OnInitialized()
    {
        GridData = new List<Product>();
        var rnd = new Random();

        for (int i = 1; i <= 12; i++)
        {
            GridData.Add(new Product()
            {
                Id = i,
                Name = "Product " + i.ToString()
            });
        }
    }

    public class Product
    {
        public int Id { get; set; }
        public string Name { get; set; }
    }
}