Selection and Focus in Blazor Grid

Sep 06, 2024
12 minutes to read

Focused Row vs. Selection

Focused and selected rows have a lot in common. For example, you can allow users to focus a row and display/update additional information outside of the grid component. You can do the same with selected rows - whether you allow single or multiple selection. The key differences between the two features are outlined below:

The focused row is a navigation feature, while selected rows facilitate operations on data rows. For example, if you navigate to a different page or filter the grid, focus can change. Row selection doesn’t change as a result of navigation or data shaping operations.
Focused row appearance usually has more contrast compared to selected rows.

Selection in Blazor Grid

The DevExpress Blazor Grid supports single and multiple row selection. Users can click rows or use a specially-designed column to select/deselect records. You can also manage selection in code.

Blazor Grid Selection

Note

Grid compares and identifies data items to ensure accurate selection operations. If your data object has a primary key, assign it to the KeyFieldName or KeyFieldNames property. Otherwise, the Grid uses standard .NET value equality comparison to identify data items.

Run Demo: Multiple Row Selection Run Demo: Selection Column Run Demo: Selection API

Single Row Selection

The DevExpress Blazor Grid supports single and multiple (default) row selection. Set the SelectionMode property to Single to allow only one row to be selected at a time.

<DxGrid Data="Products" KeyFieldName="ProductId" SelectionMode="GridSelectionMode.Single" >
    <Columns> ... </Columns>
</DxGrid>

Tip

Use the row focus feature to navigate between grid records and perform actions related to the currently focused row.

Select Rows in the UI

The grid allows users to select rows in the following ways:

Row Click

Set the AllowSelectRowByClick property to true to allow users to select rows by mouse clicks, tap gestures, and keyboard shortcuts.

<DxGrid Data="@Products" 
        KeyFieldName="ProductId"
        AllowSelectRowByClick="true"
        @bind-SelectedDataItems="@SelectedDataItems">
    <Columns>...</Columns>
</DxGrid>

The following user operations are available:

Operation	Description
Click	Click a row to select it and clear the selection of all other rows.
`Ctrl`+Click	Hold down the `Ctrl` key and click a row to add/remove the row to/from selection.
`Shift`+Click	Click the first row in a range, hold down the `Shift` key, and click the last row in the range to select a range of rows.
`Ctrl`+`Shift`+`Click`	Hold down the `Ctrl` key, click the first row in the range, hold down the `Shift` key, and click the last row in the range to add the range of rows to the selection.
`Space`	Focus a cell in a row and press `Space` to select the row and clear the selection of all other rows.
Tap	Tap a row to select it and clear the selection of all other rows.
Long Tap	Tap a row for an extended period of time to add/remove the row to/from selection.
Long Tap+Move	Tap a row for an extended period and move the finger to add a range of rows to the current selection.

Run Demo: Multiple Row Selection

Selection Column

Declare a DxGridSelectionColumn object in the Columns template to display the selection column.

<DxGrid Data="Products" KeyFieldName="ProductId">
    <Columns>
        <DxGridSelectionColumn />
        ...
    </Columns>
</DxGrid>

When the SelectionMode property is set to Multiple (the default value), the selection column displays checkboxes. Users can click them to select and deselect individual rows.

Blazor Grid Selection Column Multiple Mode

In Multiple selection mode, the selection column displays the Select All check box in the column header. A user can click this checkbox to select or deselect all rows on the current page or on all grid pages depending on the SelectAllCheckboxMode property value. Available property values are as follows:

Page: The Select All checkbox selects and deselects all rows on the current grid page. This mode changes to Mixed when the Grid is bound to a large data source and vertical virtual scrolling mode is activated.
AllPages: The Select All checkbox selects and deselects all rows on all grid pages. This mode changes to Mixed when the Grid is bound to a large data source.
Mixed: The Select All checkbox selects and deselects all rows on the current grid page. An additional drop-down button displays a context menu that allows users to select and deselect all rows on all grid pages.

<DxGrid Data="Products" 
        KeyFieldName="ProductId" 
        SelectAllCheckboxMode="GridSelectAllCheckboxMode.Mixed">
    <Columns>...</Columns>
</DxGrid>

Blazor Grid Select All Checkbox

To hide the Select All check box, disable the column’s AllowSelectAll option.

Note

The Select All check box functionality has some limitations. To learn more, see the following section: Limitations.

When the SelectionMode property is set to Single, the selection column displays radio buttons. Users can click a button to select one row at a time.

<DxGrid Data="Products" KeyFieldName="ProductId" SelectionMode="GridSelectionMode.Single">
    <Columns>
        <DxGridSelectionColumn />
        ...
    </Columns>
</DxGrid>

Blazor Grid Selection Column Single Mode

Run Demo: Selection Column

You can use the FixedPosition property to freeze the selection column and keep it visible on screen while users scroll the grid horizontally.

Select and Deselect Rows in Code

Grid implements a number of Select* and Deselect* methods that allow you to change row selection in code. The table below lists these methods.

Select* Methods	Deselect* Methods	Description
SelectRow	DeselectRow	Sets selection state of a row with the specified visible index.
SelectRows	DeselectRows	Sets selection state of rows with the specified visible indexes.
SelectDataItem	DeselectDataItem	Sets selection state of a row that corresponds to the specified data item.
SelectDataItems	DeselectDataItems	Sets selection state of rows that correspond to the specified data items.
SelectAllOnPage	DeselectAllOnPage	Sets selection state of all rows on the current visible page.
SelectAllAsync	DeselectAllAsync	Sets selection state of all rows in the grid. These methods do not affect the selection state of rows hidden by a filter.

Call the ClearSelection() method to clear selection of all rows on all pages.

Run Demo: Selection API

Obtain Selected Data Items

Single selection mode

Implement two-way binding for the SelectedDataItem property to access the data item that corresponds to the selected row. When a property value changes, the SelectedDataItemChanged event fires.

<DxGrid Data="Data" KeyFieldName="ProductId" AllowSelectRowByClick="true"
        SelectionMode="GridSelectionMode.Single"
        @bind-SelectedDataItem="@SelectedDataItem" >
    <Columns> ... </Columns>
</DxGrid>

<div>
    <p><b>Selected product:</b> @((SelectedDataItem as Product)?.ProductName ?? "(none)")</p> 
</div>

@code {
    object SelectedDataItem { get; set; }
    // ...
}

Multiple selection mode

Implement two-way binding for the SelectedDataItems property to access data items that correspond to selected rows. When a property value changes, the SelectedDataItemsChanged event fires.

Multiple Row Selection

<DxGrid Data="Data" KeyFieldName="ProductId" AllowSelectRowByClick="true"
        @bind-SelectedDataItems="@SelectedDataItems" >
    <Columns> ... </Columns>
</DxGrid>

<div>
    <b>Selected products:</b>
    @foreach (var product in SelectedDataItems.Cast<Product>()) {
        <li>@product.ProductName</li>
    }
</div>

@code {
    IReadOnlyList<object> SelectedDataItems { get; set; }
    // ...
}

The SelectedDataItemsChanged event allows you to get data items that are added to and removed from selection. For this purpose, cast the event handler’s parameter to the IGridSelectionChanges interface. The SelectedDataItems and DeselectedDataItems properties return information about selection changes.

<DxGrid Data="Data" KeyFieldName="ProductId" AllowSelectRowByClick="true"
        SelectedDataItems="@SelectedDataItems"
        SelectedDataItemsChanged="OnSelectedDataItemsChanged">
    <Columns> ... </Columns>
</DxGrid>

@code {
    // ...
    void OnSelectedDataItemsChanged(IReadOnlyList<object> newSelection) {
        if (newSelection is IGridSelectionChanges changes) {
            SelectedItemsInfo = string.Join(";  ", changes.SelectedDataItems.Cast<Product>().Select(p => p.ProductName));
            DeselectedItemsInfo = string.Join(";  ", changes.DeselectedDataItems.Cast<Product>().Select(p => p.ProductName));
        }
        SelectedDataItems = newSelection;
    }
}

Selection Limitations

When the Grid component displays all items on one page (including virtual scrolling mode), Page and AllPages modes function identically.
In virtual scrolling mode, the Grid component cannot determine the state of the Select All checkbox in Mixed mode. In such a case, the Grid sets the checkbox state to indeterminate state and displays the checkbox in read-only mode.

DevExpress Blazor Grid has the following specifics and limitations when you use a remote data source, such as Server Mode data source or GridDevExtremeDataSource:

The second call to SelectAllAsync and DeselectAllAsync method cancels the operation initiated by the previously called method.
SelectAllAsync and DeselectAllAsync methods load all data to the grid and can reduce overall performance and increase memory consumption.
If the SelectAllCheckboxMode property is set to AllPages, the DxGrid switches it to Mixed to improve performance.
In virtual scrolling mode, the DxGrid sets the SelectAllCheckboxMode property to Mixed, sets the Select All checkbox state to indeterminate state and displays the checkbox in read-only mode.

Focused Row

Set the FocusedRowEnabled property to true to allow users to focus individual grid rows. The focused row is always visible on the current grid page. If you change the current page, the focused row changes.

You can handle the FocusedRowChanged event to react to focus row change. In the following code snippet, this event is handled to display additional information about the focused employee.

<DxGrid Data="GridData" PageSize="5" FocusedRowEnabled="true" FocusedRowChanged="Grid_FocusedRowChanged">
    <Columns> ... </Columns>
</DxGrid>

<DxFormLayout>
    <DxFormLayoutItem Caption="@MemoCaption" CaptionPosition="CaptionPosition.Vertical" 
                      Visible="@ShowMemo" ColSpanMd="12">
        <DxMemo Text=@Notes Rows="4"/>
    </DxFormLayoutItem>
</DxFormLayout>

@code {
    string MemoCaption { get; set; }
    string Notes { get; set; }
    bool ShowMemo { get; set; }

    void Grid_FocusedRowChanged(GridFocusedRowChangedEventArgs e) {
        if(e.DataItem != null) {
            ShowMemo = true;
            var employee = (Employee)e.DataItem;
            MemoCaption = employee.FirstName + " " + employee.LastName + " details:";
            Notes = employee.Notes;
        }
        else {
            ShowMemo = false;
        }
    }

    object GridData { get; set; }
    protected override async Task OnInitializedAsync() {
        GridData = await NwindDataService.GetEmployeesAsync();
    }
}

Grid Focused Row

Run Demo: Focused Row

This section contain a comprehensive selection and focus-related API reference.

Show Selection API Reference

Grid API member	Type	Description
AllowSelectRowByClick	Property	Specifies whether users can select and deselect rows by mouse clicks, tap gestures, and keyboard shortcuts.
SelectAllCheckboxMode	Property	Specifies whether the Select All checkbox selects all rows on the current page or on all grid pages.
SelectionMode	Property	Specifies selection mode.
SelectedDataItem	Property	In single selection mode, this property specifies the data item that corresponds to the selected Grid row.
SelectedDataItems	Property	In multiple selection mode, this property specifies data items that corresponds to selected Grid rows.
IsDataItemSelected(Object)	Method	Returns whether the row that corresponds to the specified data item is selected.
IsRowSelected(Int32)	Method	Returns whether the specified row is selected.
ClearSelection()	Method	Clears selection.
DeselectAllAsync()	Method	Deselects all rows in the grid.
DeselectAllOnPage()	Method	Deselects all rows on the current visible page.
DeselectDataItem(Object)	Method	Deselects a row that corresponds to the specified data item.
DeselectDataItems(IEnumerable<Object>)	Method	Deselects rows that correspond to the specified data items.
DeselectRow(Int32)	Method	Deselects a row with the specified visible index.
DeselectRows(IEnumerable<Int32>)	Method	Deselects rows with the specified visible indexes.
SelectAllAsync(Boolean)	Method	Selects or deselects all rows in the grid.
SelectAllOnPage(Boolean)	Method	Selects or deselects all rows on the current visible page.
SelectDataItem(Object, Boolean)	Method	Selects or deselects a row that corresponds to the specified data item.
SelectDataItems(IEnumerable<Object>, Boolean)	Method	Selects or deselects rows that correspond to the specified data items.
SelectRow(Int32, Boolean)	Method	Selects or deselects a row with the specified visible index.
SelectRows(IEnumerable<Int32>, Boolean)	Method	Selects or deselects rows with the specified visible indexes.
SelectedDataItemChanged	Event	In single selection mode, fires when another Grid row is selected.
SelectedDataItemsChanged	Event	In multiple selection mode, fires when the selection in the Grid changes.

Selection Column API member	Type	Description
AllowSelectAll	Property	Specifies whether the selection column contains the Select All checkbox.
CellDisplayTemplate	Property	Specifies a template for selection column cells.
FilterRowCellTemplate	Property	Specifies a template for the selection column’s filter row cell.
HeaderTemplate	Property	Specifies a template for the selection column header.

Export API member	Type	Description
GridExportOptionsBase.ExportSelectedRowsOnly	Property	Specifies if the grid exports only selected rows.

Show Focus API Reference

Grid API member	Type	Description
FocusedRowEnabled	Property	Specifies whether the row focus is enabled.
GetFocusedDataItem()	Method	Returns a data item bound to the focused data row.
GetFocusedRowIndex()	Method	Returns the visible index of the focused row.
IsDataItemFocused(Object)	Method	Identifies whether the row bound to the specified data item is focused.
IsRowFocused(Int32)	Method	Identifies whether the row with the specified visible index is focused.
SetFocusedDataItemAsync(Object)	Method	Moves focus to the row bound to the specified data item.
SetFocusedRowIndex(Int32)	Method	Moves focus to the row with the specified visible index.
FocusedRowChanged	Event	Fires when the row focus changes.

GitHub Examples

Online Demos

Task-Based Examples

This section contains code samples that demonstrate row selection functionality.

Scroll Grid to the Selected Data Item

Pass the SelectedDataItem object to the MakeDataItemVisibleAsync(Object) method to scroll data to the row bound to the specified data item.

Grid.MakeDataItemVisibleAsync(Grid.SelectedDataItem);

Limit the Number of Selected Rows

The SelectedDataItemsChanged event fires when the selection in the Grid changes. Handle this event to determine the number of selected rows and deselect them if the number of selected rows exceeds a predefined maximum value.

<DxGrid @ref=Grid Data="@forecasts" 
        SelectedDataItems="SelectedItems"
        SelectedDataItemsChanged="Grid_SelectedDataItemsChanged">
    <Columns>
        <DxGridSelectionColumn />
        <DxGridDataColumn FieldName="Date" />
        <DxGridDataColumn FieldName="TemperatureF" />
    </Columns>
</DxGrid>

@code {
    int maxSelectedRowCount = 3; 
    private WeatherForecast[]? forecasts;
    IReadOnlyList<object> SelectedItems;
    IGrid Grid;

    void Grid_SelectedDataItemsChanged(IReadOnlyList<object> newSelection) {
        SelectedItems = newSelection;
        if (newSelection?.Count > maxSelectedRowCount)
            Grid.DeselectDataItems(newSelection.Skip(maxSelectedRowCount));
    }

    protected override async Task OnInitializedAsync() {
        forecasts = await ForecastService.GetForecastAsync(DateTime.Now);
    }
}

How to Get a Notification When the Select All Checkbox State Changes

There is no event to notify that the Select All checkbox is clicked. You can create your own template to reproduce the default render and observe the checkbox’s state.

<DxGrid Data="GridData">
    <Columns>
        <DxGridSelectionColumn>
            <HeaderTemplate>
                <DxCheckBox T="bool?"
                            Checked="context.Selected"
                            CheckedChanged="(newValue) => SelectAllCheckboxClicked(newValue, context)"/>
            </HeaderTemplate>
        </DxGridSelectionColumn>
        <DxGridDataColumn FieldName="OrderID" />
        <DxGridDataColumn FieldName="OrderDate" />
    </Columns>
</DxGrid>

@code {
    void SelectAllCheckboxClicked(bool? newValue, GridSelectionColumnHeaderTemplateContext context) {
        context.Selected = newValue!.Value;
        // .. your actions here
    }
}

How to Suppress Row Selection When a Certain Element in Grid is Clicked

When the AllowSelectRowByClick property is set to true, users can click rows to select them. If your grid contains links or custom buttons, a click on the element initiates the element-related action, then the RowClick event fires and the row is selected. Use the stopPropagation directive attribute to prevent the click from triggering Grid events. In this case, clicking these links or buttons does not cause row selection.

<DxGridDataColumn FieldName="TotalPrice" DisplayFormat="c" UnboundType="GridUnboundColumnType.Decimal">
    <CellDisplayTemplate>
        <a @onclick:stopPropagation @onclick="() => ShowDetails()">More Info</a>
        @* or *@
        <div @onclick:stopPropagation="true">
            @* Custom buttons *@
        </div>
    </CellDisplayTemplate>
</DxGridDataColumn>

How to Use a Custom Checkbox Inside a Selection Column

To replace selection column editors with custom checkboxes, place the DxCheckBox<T> component in CellDisplayTemplate and implement two-way binding to bind the Checked checkbox property to the context.Selected value.

<DxGridSelectionColumn Width="104px">
    <CellDisplayTemplate Context="SelContext">
        <DxCheckBox @bind-Checked="SelContext.Selected"  />
    </CellDisplayTemplate>
</DxGridSelectionColumn>

Select Rows in a Group

To allow users to select and deselect all rows in a group, implement the DataColumnGroupRowTemplate template. Place the DxCheckBox<T> component in the template and handle checked state changes.

Custom Sorted Groups

You can see a complete code sample in the following GitHub example: Select and Deselect All Rows in a Group

Controls

Tools

Controls and Extensions

Tools

Maintenance Mode

Controls

Tools

Controls and Extensions

Tools

Maintenance Mode

Focused Row vs. Selection

Selection in Blazor Grid

Single Row Selection

Select Rows in the UI

Row Click

Selection Column

Select and Deselect Rows in Code

Obtain Selected Data Items

Single selection mode

Multiple selection mode

Selection Limitations

Focused Row

GitHub Examples

Online Demos

Task-Based Examples

Scroll Grid to the Selected Data Item

Limit the Number of Selected Rows

How to Get a Notification When the Select All Checkbox State Changes

How to Suppress Row Selection When a Certain Element in Grid is Clicked

How to Use a Custom Checkbox Inside a Selection Column

Select Rows in a Group

Selection and Focus in Blazor Grid

Focused Row vs. Selection

Selection in Blazor Grid

Single Row Selection

Select Rows in the UI

Row Click

Selection Column

Select and Deselect Rows in Code

Obtain Selected Data Items

Single selection mode

Multiple selection mode

Selection Limitations

Focused Row

Related API

GitHub Examples

Online Demos

Task-Based Examples

Scroll Grid to the Selected Data Item

Limit the Number of Selected Rows

How to Get a Notification When the Select All Checkbox State Changes

How to Suppress Row Selection When a Certain Element in Grid is Clicked

How to Use a Custom Checkbox Inside a Selection Column

Select Rows in a Group