aspnet-11579-components-grid-view-concepts-filter-data-header-filter.md
The ASPxGridView control implements a column header filter that displays a dropdown list of all unique values within a column.
The following properties specify the filter button’s availability:
ShowHeaderFilterButtonControls visibility of every column’s filter button.AllowHeaderFilterControls visibility of a specific column’s filter button.
Users can enter text in the filter editor above the list to filter list items. To hide the filter editor, set the ShowHeaderFilterListBoxSearchUI property to false.
When you apply a filter to a column, the other header filters display values that relate to the specified filter criteria. Hold down Shift and click the header filter button to show the full list of values.
Run Demo: Header FilterRun Demo: Range Header Filter
Use the Mode property to specify a column’s filter mode. You can set the following filter modes for a grid data column.
ListThe header filter is displayed as a regular list of filter items. Clicking an item invokes a corresponding action and automatically closes the dropdown.CheckedListThe header filter is displayed as a checked list of filter items. In this mode, an end-user can select more than one item simultaneously. When the dropdown window is closed by clicking the OK button, the grid will display those records that contain the checked values.DateRangeCalendar(For date columns only). The header filter displays a calendar and a set of predefined items. Use the SettingsHeaderFilter.DateRangeCalendarSettings property to customize the calendar settings.DateRangePicker(For date columns only). The header filter displays a date range picker and a set of predefined items. Use the SettingsHeaderFilter.DateRangePickerSettings property to customize the editor settings.NumericRangePicker(For numeric columns only). The header filter displays two spin editors and a track bar. Use the NumericRangeSpinEditSettings and NumericRangeTrackBarSettings properties to customize settings of the spin editors and track bar.
The ASPxGridView control allows you to create custom filter values, define their filter criteria, and display these values within a column’s drop-down filter.
You can handle the following events to customize the header filter items:
BeforeHeaderFilterFillItemsAllows you to populate the header filter dropdown with custom items instead of default items.HeaderFilterFillItemsAllows you to add custom header filter items to default items.
This example creates custom filter items and displays them within the Units On Order column’s filter dropdown.
protected void ASPxGridView1_HeaderFilterFillItems(object sender, DevExpress.Web.ASPxGridViewHeaderFilterEventArgs e) {
if (e.Column.FieldName != "Quantity") return;
e.AddValue("nonzero", string.Empty, "[Quantity] != 0");
e.AddValue(String.Format("from {0} to {1}", 0, 50), string.Empty, String.Format("[Quantity] > {0} and [Quantity] < {1}", 0, 50));
e.AddValue(String.Format(">= {0}", 50), string.Empty, String.Format("[Quantity] >= {0}", 50));
}
Protected Sub ASPxGridView1_HeaderFilterFillItems(ByVal sender As Object, ByVal e As DevExpress.Web.ASPxGridViewHeaderFilterEventArgs)
If e.Column.FieldName <> "Quantity" Then Return
e.AddValue("nonzero", String.Empty, "[Quantity] != 0")
e.AddValue(String.Format("from {0} to {1}", 0, 50), String.Empty, String.Format("[Quantity] > {0} and [Quantity] < {1}", 0, 50))
e.AddValue(String.Format(">= {0}", 50), String.Empty, String.Format("[Quantity] >= {0}", 50))
End Sub
The ASPxGridView header filter allows you to use HTML tags in an item’s text. This example uses HTML tags within an item’s format pattern to make numbers bold. The image below shows the result.
protected void grid_HeaderFilterFillItems(object sender, ASPxGridViewHeaderFilterEventArgs e) {
if(e.Column.FieldName == "Quantity")
PrepareQuantityFilterItems(e);
}
protected virtual void PrepareQuantityFilterItems(ASPxGridViewHeaderFilterEventArgs e) {
int max = 0;
for(int i = 0; i < e.Values.Count; i++) {
int value;
if(!int.TryParse(e.Values[i].Value, out value)) continue;
if(value > max) max = value;
}
e.Values.Clear();
int step = 10;
for(int i = 0; i < max / step + 1; i++) {
int start = step * i;
int end = start + step - 1;
e.AddValue(string.Format("from <b>{0}</b> to <b>{1}</b>", start, end), "", string.Format("[Quantity] >= {0} and [Quantity] <= {1}", start, end));
}
}
Protected Sub grid_HeaderFilterFillItems(ByVal sender As Object, ByVal e As ASPxGridViewHeaderFilterEventArgs)
If e.Column.FieldName = "Quantity" Then
PrepareQuantityFilterItems(e)
End If
End Sub
Protected Overridable Sub PrepareQuantityFilterItems(ByVal e As ASPxGridViewHeaderFilterEventArgs)
Dim max As Integer = 0
For i As Integer = 0 To e.Values.Count - 1
Dim value As Integer
If (Not Integer.TryParse(e.Values(i).Value, value)) Then
Continue For
End If
If value > max Then
max = value
End If
Next i
e.Values.Clear()
Dim [step] As Integer = 10
For i As Integer = 0 To max / [step]
Dim start As Integer = [step] * i
Dim [end] As Integer = start + [step] - 1
e.AddValue(String.Format("from <b>{0}</b> to <b>{1}</b>", start, [end]), "", String.Format("[Quantity] >= {0} and [Quantity] <= {1}", start, [end]))
Next i
End Sub
Set the AccessibilityCompliant property to true to enable keyboard navigation in the control. Users can use the following keys to work with header filters.
TabFocuses the filter buttons.EnterOpens a header filter popup window. / Closes the header filter pop-up window and applies the filter criteria.Up and Down arrowsNavigate the list of filter items in List mode.TabNavigates the list of filter items in CheckedList mode.EscCloses the header filter pop-up window and cancels the changes.Shift + header filter button clickShows all the values (including hidden rows’ values).