@page "/"

<TelerikGrid Data=@GridData
             SelectionMode="GridSelectionMode.Multiple"
             SelectedItemsChanged="@((IEnumerable<Employee> employeeList) => OnSelect(employeeList))"
             SelectedItems="@PersistedSelectedItems"
             @bind-Page="@CurrentPage"
             PageSize="@PageSize"
             Pageable="true"
             FilterMode="GridFilterMode.FilterRow"
             OnStateChanged="@((GridStateEventArgs<Employee> args) => OnStateChangedHandler(args))">
    <GridColumns>
        <GridCheckboxColumn />
        <GridColumn Field=@nameof(Employee.EmployeeId) />
        <GridColumn Field=@nameof(Employee.Name) />
        <GridColumn Field=@nameof(Employee.Team) />
    </GridColumns>
</TelerikGrid>

@if (PersistedSelectedItems != null)
{
    <ul>
        @foreach (Employee employee in PersistedSelectedItems.OrderBy(e => e.EmployeeId))
        {
            <li>
                @employee.EmployeeId
            </li>
        }
    </ul>
}

@code {
    public List<Employee> PersistedSelectedItems { get; set; } = new List<Employee>();
    int CurrentPage { get; set; }
    int PageSize { get; set; } = 5;

    private async void OnStateChangedHandler(GridStateEventArgs<Employee> args)
    {
        await Task.Delay(5000);
    }

    protected void OnSelect(IEnumerable<Employee> employees)
    {
        IEnumerable<Employee> CurrentPageEmployees = GridData.Skip(PageSize * (CurrentPage - 1)).Take(PageSize);

        if (employees == null || employees.Count() == 0)
        {
            //the user de-selected all items with the header checkbox
            PersistedSelectedItems = PersistedSelectedItems.Except(CurrentPageEmployees).ToList();
        }
        else
        {
            //handle any deselected items
            var UnselectedEmployees = CurrentPageEmployees.Except(employees);
            PersistedSelectedItems = PersistedSelectedItems.Except(UnselectedEmployees).ToList();

            //add any new items if they were not selected already
            foreach (var item in employees)
            {
                if (!PersistedSelectedItems.Contains(item))
                {
                    PersistedSelectedItems.Add(item);
                }
            }
        }
    }

    //data binding and sample data
    public List<Employee> GridData { get; set; }

    protected override void OnInitialized()
    {
        GridData = new List<Employee>();
        for (int i = 0; i < 15; i++)
        {
            GridData.Add(new Employee()
            {
                EmployeeId = i,
                Name = "Employee " + i.ToString(),
                Team = "Team " + i % 3
            });
        }
    }

    public class Employee
    {
        public int EmployeeId { get; set; }
        public string Name { get; set; }
        public string Team { get; set; }
    }
}

@using Telerik.DataSource
@using Telerik.DataSource.Extensions

@( new MarkupString(output) )

<br />
<TelerikButton OnClick="@GetFilters">Get Filters</TelerikButton>


<TelerikGrid Data=@GridData TotalCount=@Total OnRead=@ReadItems
             FilterMode=@GridFilterMode.FilterRow Sortable=true Pageable=true EditMode="@GridEditMode.Inline">
    <GridToolBar>
        <GridSearchBox />
    </GridToolBar>
    <GridColumns>
        <GridColumn Field=@nameof(Employee.ID) />
        <GridColumn Field=@nameof(Employee.Name) Title="Name" />
        <GridColumn Field=@nameof(Employee.HireDate) Title="Hire Date" />
        <GridCommandColumn>
            <GridCommandButton Command="Save" Icon="save" ShowInEdit="true">Update</GridCommandButton>
            <GridCommandButton Command="Edit" Icon="edit">Edit</GridCommandButton>
            <GridCommandButton Command="Delete" Icon="delete">Delete</GridCommandButton>
            <GridCommandButton Command="Cancel" Icon="cancel" ShowInEdit="true">Cancel</GridCommandButton>
        </GridCommandColumn>
    </GridColumns>
</TelerikGrid>

@code {
    TelerikGrid<Employee> GridRef { get; set; }
    string output { get; set; }
    public DataSourceRequest CurrentRequest { get; set; }
    void GetFilters()
    {
        output = string.Empty;


        foreach (var item in CurrentRequest.Filters)
        {
            if (item is FilterDescriptor) // filter row
            {
                FilterDescriptor currFilter = item as FilterDescriptor;
                output += $"field: {currFilter.Member}, operator {currFilter.Operator}, value: {currFilter.Value}<br />";
            }

            if (item is CompositeFilterDescriptor) // filter menu
            {
                CompositeFilterDescriptor currFilter = item as CompositeFilterDescriptor;
                output += $"START nested filter: logical operator: {currFilter.LogicalOperator}, details:<br />";
                // there will actually be 1 or 2 only, this showcases the concept and the types
                foreach (FilterDescriptor nestedFilter in currFilter.FilterDescriptors)
                {

                    output += $"field: {nestedFilter.Member}, operator {nestedFilter.Operator}, value: {nestedFilter.Value}<br />";
                }
                output += "END nested filter<br />";
            }
        }
    }




    public List<Employee> SourceData { get; set; }
    public List<Employee> GridData { get; set; }
    public int Total { get; set; } = 0;

    protected override void OnInitialized()
    {
        SourceData = GenerateData();
    }

    protected async Task ReadItems(GridReadEventArgs args)
    {
        CurrentRequest = args.Request;


        var datasourceResult = SourceData.ToDataSourceResult(args.Request);

        GridData = (datasourceResult.Data as IEnumerable<Employee>).ToList();
        Total = datasourceResult.Total;

        StateHasChanged();
    }

    //This sample implements only reading of the data. To add the rest of the CRUD operations see
    //https://docs.telerik.com/blazor-ui/components/grid/editing/overview

    private List<Employee> GenerateData()
    {
        var result = new List<Employee>();
        var rand = new Random();
        for (int i = 0; i < 100; i++)
        {
            result.Add(new Employee()
            {
                ID = i,
                Name = "Name " + i,
                HireDate = DateTime.Now.Date.AddDays(rand.Next(-20, 20))
            });
        }

        return result;
    }

    public class Employee
    {
        public int ID { get; set; }
        public string Name { get; set; }
        public DateTime HireDate { get; set; }
    }
}

@inject IJSRuntime js

<TelerikGrid Data="@GridData"
             Pageable="true"
             Sortable="true"
             Class="custom-grid-class">
    <GridToolBarTemplate>
        <GridSearchBox />
        <TelerikButton Icon="@SvgIcon.X" OnClick="@OnClearButtonClick"></TelerikButton>
    </GridToolBarTemplate>
    <GridColumns>
        <GridColumn Field="@nameof(SampleModel.Name)" />
        <GridColumn Field="@nameof(SampleModel.Description)" />
    </GridColumns>
</TelerikGrid>

<script suppress-error="BL9992">//
    function clearSearch() {
        // locate the searchbox of the Grid
        const input = document.querySelector(".custom-grid-class .k-grid-search input");
        // clear the value of the input
        input.value = "";
        // dispatch the input event in order to force the Grid event binding to trigger the filtering
        input.dispatchEvent(new Event('input', {bubbles: true} ));
    }
//</script>

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

    private async Task OnClearButtonClick()
    {
        await js.InvokeVoidAsync("clearSearch");
    }

    protected override void OnInitialized()
    {
        for (int i = 1; i <= 50; i++)
        {
            GridData.Add(new SampleModel()
            {
                Id = i,
                Name = $"{(char)(64 + i % 26 + 1)}{(char)(64 + i % 26 + 1)} {i}",
                Description = $"{(char)(123 - i % 26 - 1)}{(char)(123 - i % 26 - 1)} {i}"
            });
        }
    }

    public class SampleModel
    {
        public int Id { get; set; }
        public string Name { get; set; } = string.Empty;
        public string Description { get; set; } = string.Empty;
    }
}

Error: System.InvalidOperationException: No generic method 'Sum' on type 'System.Linq.Enumerable' is compatible with the supplied type arguments and arguments. No type arguments should be provided if the method is non-generic. 
   at System.Linq.Expressions.Expression.FindMethod(Type type, String methodName, Type[] typeArgs, Expression[] args, BindingFlags flags)
   at System.Linq.Expressions.Expression.Call(Type type, String methodName, Type[] typeArguments, Expression[] arguments)
   at Telerik.DataSource.Expressions.EnumerableSelectorAggregateFunctionExpressionBuilder.CreateMethodCallExpression(LambdaExpression memberSelectorExpression)
   at Telerik.DataSource.Expressions.EnumerableSelectorAggregateFunctionExpressionBuilder.CreateAggregateExpression()
   at Telerik.DataSource.EnumerableSelectorAggregateFunction.CreateAggregateExpression(Expression enumerableExpression, Boolean liftMemberAccessToNull)
   at Telerik.DataSource.Expressions.GroupDescriptorExpressionBuilder.<ProjectionPropertyValueExpressions>b__39_0(AggregateFunction f)
   at System.Linq.Enumerable.SelectIListIterator`2.ToList()
   at Telerik.DataSource.Expressions.GroupDescriptorExpressionBuilder.CreateProjectionInitExpression()
   at Telerik.DataSource.Expressions.GroupDescriptorExpressionBuilder.CreateAggregateFunctionsProjectionMemberBinding()
   at Telerik.DataSource.Expressions.QueryableAggregatesExpressionBuilder.CreateMemberBindings()+MoveNext()
   at System.Collections.Generic.LargeArrayBuilder`1.AddRange(IEnumerable`1 items)
   at System.Collections.Generic.EnumerableHelpers.ToArray[T](IEnumerable`1 source)
   at System.Linq.Enumerable.ToArray[TSource](IEnumerable`1 source)
   at System.Dynamic.Utils.CollectionExtensions.ToReadOnly[T](IEnumerable`1 enumerable)
   at System.Linq.Expressions.Expression.MemberInit(NewExpression newExpression, IEnumerable`1 bindings)
   at Telerik.DataSource.Expressions.GroupDescriptorExpressionBuilder.CreateSelectBodyExpression()
   at Telerik.DataSource.Expressions.GroupDescriptorExpressionBuilder.CreateSelectExpression()
   at Telerik.DataSource.Expressions.GroupDescriptorExpressionBuilderBase.CreateQuery()
   at Telerik.DataSource.Extensions.QueryableExtensions.Aggregate(IQueryable source, IEnumerable`1 aggregateFunctions)
   at Telerik.DataSource.Extensions.QueryableExtensions.CreateDataSourceResult[TModel,TResult](IQueryable queryable, DataSourceRequest request, Func`2 selector)
   at Telerik.DataSource.Extensions.QueryableExtensions.ToDataSourceResult(IQueryable queryable, DataSourceRequest request)
   at Telerik.DataSource.Extensions.QueryableExtensions.ToDataSourceResult(IEnumerable enumerable, DataSourceRequest request)
   at Telerik.Blazor.Data.TelerikDataSourceBase.ProcessData(IEnumerable data)
   at Telerik.Blazor.Components.Common.DataBoundComponent`1.ProcessDataInternal()
   at Telerik.Blazor.Components.Common.DataBoundComponent`1.ProcessDataAsync()
   at Telerik.Blazor.Components.TelerikGrid`1.DataBoundProcessData()
   at Telerik.Blazor.Components.TelerikGrid`1.ProcessDataAsync()
   at Telerik.Blazor.Components.TelerikGrid`1.ApplyFiltersAsync()
   at Telerik.Blazor.Components.TelerikGrid`1.OnFilterChange(FilterDescriptorBase filter)
   at Telerik.Blazor.Components.Common.Filters.TelerikFilterHeader`1.Filter(FilterDescriptor filterDescriptor)
   at Telerik.Blazor.Components.Common.Filters.TelerikFilterHeader`1.OnValueChanged(Object newValue)
   at System.Threading.Tasks.Task.<>c.<ThrowAsync>b__139_0(Object state)
   at Microsoft.AspNetCore.Components.Rendering.RendererSynchronizationContext.ExecuteSynchronously(TaskCompletionSource`1 completion, SendOrPostCallback d, Object state)
   at Microsoft.AspNetCore.Components.Rendering.RendererSynchronizationContext.<>c.<.cctor>b__23_0(Object state)
   at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state)
--- End of stack trace from previous location where exception was thrown ---
   at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
   at Microsoft.AspNetCore.Components.Rendering.RendererSynchronizationContext.ExecuteBackground(WorkItem item)

<TelerikGrid Data="@MyData" Height="300px" Pageable="true" Sortable="true" FilterMode="@GridFilterMode.FilterMenu" Reorderable="true">
    <GridColumns>
        <GridColumn Field="@(nameof(SampleData.ID))" Title="This title will not be rendered">
            <HeaderTemplate>
                Continent <br />
                <div style="text-align:center">Id</div>
                <div @onclick:stopPropagation="true" data-draggable="false">
                    <TelerikComboBox Data="@Continents" Filterable="true" class="headerCombo"
                                     @bind-Value="@SelectedContinentId"
                                     TextField="@nameof(Continent.Name)" ValueField="@nameof(Continent.Id)" Id="MyId">
                    </TelerikComboBox>
                </div>
            </HeaderTemplate>
        </GridColumn>
        <GridColumn Field=@nameof(SampleData.Name) Title="First Name" />
    </GridColumns>
</TelerikGrid>

@code {
    /* Grid */
    string result { get; set; }
    void DoSomething()
    {
        result = $"button in header template clicked on {DateTime.Now}, something happened";
    }

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

    public IEnumerable<SampleData> MyData = Enumerable.Range(1, 50).Select(x => new SampleData
    {
        ID = x,
        Name = "name " + x,
        HireDate = DateTime.Now.AddDays(-x)
    });

    /* ComboBox */

    public class Continent
    {
        public int Id { get; set; }
        public string Name { get; set; }
    }
    IEnumerable<Continent> Continents = new List<Continent>() { new Continent { Id = 1, Name = "Africa" }, new Continent { Id = 2, Name = "Asia" }, new Continent { Id = 3, Name = "South America" } };
    public int SelectedContinentId { get; set; } = 1;

}