@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; }
    }
}

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

<TelerikGrid Data="@GridData" EditMode="@GridEditMode.Incell" Navigable="true"
             OnEdit="@EditItem" OnUpdate="@UpdateItem">
    <GridColumns>
        <GridColumn Field="@nameof(GridModel.Foo)" Title="Foo (bug)" />
        <GridColumn Field="@nameof(GridModel.Bar)" Title="Bar (workaround)">
            @*<EditorTemplate>
                @{
                    var item = context as GridModel;
                    // workaround 1
                    if (item.IsEditable)
                    {
                        <TelerikTextBox @bind-Value="@item.Bar" />
                    }
                    else
                    {
                        <span class="k-textbox k-input k-rounded-md">
                            <input class="k-input-inner" tabindex="0" readonly value="@item.Bar" />
                        </span>
                    }
                }
            </EditorTemplate>*@
        </GridColumn>
        <GridColumn Field="@nameof(GridModel.IsEditable)" Title="Is Row Editable?" Editable="false" />
    </GridColumns>
</TelerikGrid>

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

    void EditItem(GridCommandEventArgs args)
    {
        GridModel item = args.Item as GridModel;
        if (!item.IsEditable)
        {
            args.IsCancelled = true;
        }
    }

    void UpdateItem(GridCommandEventArgs args)
    {
        var argsItem = args.Item as GridModel;
        var index = GridData.FindIndex(i => i.Id == argsItem.Id);
        // workaround 2
        //if (index != -1 && argsItem.IsEditable)
        //{
            GridData[index] = argsItem;
        //}
    }

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

        for (int i = 1; i <= 5; i++)
        {
            GridData.Add(new GridModel()
            {
                Id = i,
                Foo = "Foo " + i.ToString(),
                Bar = "Bar " + i.ToString(),
                IsEditable = i % 2 == 0
            });
        }
    }

    public class GridModel
    {
        public int Id { get; set; }
        public string Foo { get; set; }
        public string Bar { get; set; }
        public bool IsEditable { get; set; }
    }
}

@using Telerik.DataSource
@using Telerik.DataSource.Extensions
@using System.IO

<TelerikGrid TItem="@object"
             LoadGroupsOnDemand="true"
             Groupable="true"
             OnStateInit="@((GridStateEventArgs<object> args) => OnStateInitHandler(args))"
             OnRead="@ReadItems"
             ScrollMode="@GridScrollMode.Virtual" PageSize="20" RowHeight="60"
             Navigable="true" Sortable="true" FilterMode="@GridFilterMode.FilterRow" Height="600px">
    <GridColumns>
        <GridColumn Field="@nameof(Employee.Name)" FieldType="@typeof(string)" Groupable="false" />
        <GridColumn Field="@nameof(Employee.Team)" FieldType="@typeof(string)" Title="Team" />
        <GridColumn Field="@nameof(Employee.Salary)" FieldType="@typeof(decimal)" Groupable="false" />
        <GridColumn Field="@nameof(Employee.IsOnLeave)" FieldType="@typeof(bool)" Title="On Vacation" />
    </GridColumns>
</TelerikGrid>

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

    protected async Task ReadItems(GridReadEventArgs args)
    {
        DataEnvelope<Employee> result = await MyService.GetData(args.Request);

        if (args.Request.Groups.Count > 0)
        {
            args.Data = result.GroupedData.Cast<AggregateFunctionsGroup>().ToList();
        }
        else
        {
            args.Data = result.CurrentPageData.Cast<Employee>().ToList();
        }

        args.Total = result.TotalItemCount;

        if (args.Request.Groups.Count > 0)
        {
            try
            {
                List<AggregateFunctionsGroup> items = result.GroupedData.Cast<AggregateFunctionsGroup>().ToList();

                await using var s = new MemoryStream();
                await System.Text.Json.JsonSerializer.SerializeAsync(s, items);
            }
            catch (Exception e)
            {
                Console.WriteLine(e);
            }
        }
    }

    void OnStateInitHandler(GridStateEventArgs<object> args)
    {
        // set initial grouping
        GridState<object> desiredState = new GridState<object>()
        {
            GroupDescriptors = new List<GroupDescriptor>()
    {
                new GroupDescriptor()
                {
                    Member = "Team",
                    MemberType = typeof(string)
                },
                new GroupDescriptor()
                {
                    Member = "IsOnLeave",
                    MemberType = typeof(bool)
                }
            }
        };

        args.GridState = desiredState;
    }

    public class Employee
    {
        public int EmployeeId { get; set; }
        public string Name { get; set; }
        public string Team { get; set; }
        public bool IsOnLeave { get; set; }
        public decimal Salary { get; set; }
    }

    public class DataEnvelope<T>
    {
        public List<AggregateFunctionsGroup> GroupedData { get; set; }
        public List<T> CurrentPageData { get; set; }
        public int TotalItemCount { get; set; }
    }

    public static class MyService
    {
        private static List<Employee> SourceData { get; set; }
        public static async Task<DataEnvelope<Employee>> GetData(DataSourceRequest request)
        {
            if (SourceData == null)
            {
                SourceData = new List<Employee>();
                var rand = new Random();
                for (int i = 1; i <= 2500; i++)
                {
                    SourceData.Add(new Employee()
                    {
                        EmployeeId = i,
                        Name = "Employee " + i.ToString(),
                        Team = "Team " + i % 100,
                        IsOnLeave = i % 3 == 0,
                        Salary = rand.Next(1000, 5000)
                    });
                }
            }

            await Task.Delay(500);// deliberate delay to showcase async operations, remove in a real app

            // retrieve data as needed, you can find more examples and runnable projects here
            // https://github.com/telerik/blazor-ui/tree/master/grid/datasourcerequest-on-server
            var datasourceResult = SourceData.ToDataSourceResult(request);

            DataEnvelope<Employee> dataToReturn;

            if (request.Groups.Count > 0)
            {
                dataToReturn = new DataEnvelope<Employee>
                {
                    GroupedData = datasourceResult.Data.Cast<AggregateFunctionsGroup>().ToList(),
                    TotalItemCount = datasourceResult.Total
                };
            }
            else
            {
                dataToReturn = new DataEnvelope<Employee>
                {
                    CurrentPageData = datasourceResult.Data.Cast<Employee>().ToList(),
                    TotalItemCount = datasourceResult.Total
                };
            }

            return await Task.FromResult(dataToReturn);
        }
    }
}

    DataSourceRequest request1 = new()
    {
         Filters = new[] {new FilterDescriptor("Test", FilterOperator.IsEqualTo, DateTime.Now.Date) {MemberType = typeof(DateTime)}},
         Sorts = new List<SortDescriptor>()
    };

    DataSourceRequest request2 = new()
    {
         Filters = new[] { new FilterDescriptor("Test", FilterOperator.IsEqualTo, DateTime.Now.Date) { MemberType = typeof(DateTime?) } },
         Sorts = new List<SortDescriptor>()
    };

    string query1 = request1.ToODataString(); // outputs $count=true&$filter=(Test%20eq%202022-05-12T00:00:00.0000000Z)&$skip=0
    string query2 = request2.ToODataString(); // outputs $count=true&$filter=(Test%20eq%202022-05-12%2000:00:00)&$skip=0