@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; }
    }
}

// locate the searchbox of the Grid
const input = document.querySelector(".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} ));

<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;

}

<style>
    .k-group-footer + .k-group-footer {
       display:none;
    }
</style>

Group by the Vacation and Team columns to see the effect

<TelerikGrid Data=@GridData Groupable="true" Pageable="true">
    <GridColumns>
        <GridColumn Field=@nameof(Employee.Name) Groupable="false" />
        <GridColumn Field=@nameof(Employee.Team) Title="Team">
            <GroupFooterTemplate>
                Team group footer
            </GroupFooterTemplate>
        </GridColumn>
        <GridColumn Field=@nameof(Employee.IsOnLeave) Title="On Vacation">
            <GroupFooterTemplate>
                IsOnLeave group footer
            </GroupFooterTemplate>
            </GridColumn>
    </GridColumns>
</TelerikGrid>

@code {
    public List<Employee> GridData { get; set; }

    protected override void OnInitialized()
    {
        GridData = new List<Employee>();
        var rand = new Random();
        for (int i = 0; i < 15; i++)
        {
            GridData.Add(new Employee()
            {
                EmployeeId = i,
                Name = "Employee " + i.ToString(),
                Team = "Team " + i % 3,
                IsOnLeave = i % 2 == 0
            });
        }
    }

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