The value of this option will be passed to the accesskey attribute of the HTML element that underlies the widget.

This option is used when the widget is displayed on a platform whose guidelines include the active state change for widgets.

The option accepts the following values.

• 'useButtons'
  Enables an end-user to apply the selected value or cancel the selection using the Apply and Cancel buttons respectively.

• 'instantly'
  Applies the selected value immediately after a user clicks the required value in the drop-down menu. To cancel the selection, click outside the drop-down menu.

When using the widget as an ASP.NET MVC Control, specify this option using the EditorApplyValueMode enum. This enum accepts the following values: Instantly and UseButtons.

The function passed to this option enables you to specify a custom condition for widget closing. For instance, you can prevent closing until a user clicks a certain element.

$(function () {
    $("#lookupContainer").dxLookup({
        // ...
        closeOnOutsideClick: function(e) {
            return e.target === $("#someElement").get()[0];
        }
    });
});

import { DxLookupModule } from 'devextreme-angular';
// ...
export class AppComponent {
    // ...
    closeOnOutsideClick (e) {
        return e.target === document.getElementById("someElement");
    }
}
@NgModule({
     imports: [
         // ...
         DxLookupModule
     ],
     // ...
 })

<dx-lookup ...
    (closeOnOutsideClick)="closeOnOutsideClick($event)">
</dx-lookup>

This option accepts one of the following.

• Array of objects
  A simple JavaScript array containing a collection of plain objects.

• URL
  A URL to JSON data or to a service returning data in JSON format.

• DataSource or its configuration object
  A DataSource is an object that provides a handy API for data processing. A DataSource is a stateful object, which means that it saves data processing settings and applies them each time data is loaded. All underlying data access logic of a DataSource is isolated in a Store. A Store provides an API for reading and modifying data. Unlike the DataSource, a Store is a stateless object.

If the data source is specified using the dataSource option, use the items option only for reading. Updating data items using the items option may cause unexpected results.

If the Lookup widget works with the data accessed using a DataSource instance wrapping a CustomStore, pay attention to the byKey option of the CustomStore instance, which is required for this widget. This option takes on a function used to get an item by a key.

To display widget items, a default template can be used. This template is based on the data source fields that are listed in the Default Item Template section of the widget's API. Alternatively, you can implement a custom item template.

If the data source item is a simple object holding a value (string, numeric, Boolean, etc.), assign 'this' to the displayExpr option. If the item is a plain object item, assign the required field name or path to the option.

The value you pass to this option does not affect widget behavior. Pass an observable variable to this option to get the value currently displayed by the widget.

See Also

• SelectBox - Customize Drop-Down Button Demo
• Custom Templates

You can configure this option in an ASP.NET MVC Control as follows:

@(Html.DevExtreme().WidgetName()
    .ElementAttr("class", "class-name")
    // ===== or =====
    .ElementAttr(new {
        @id = "elementId",
        @class = "class-name"
    })
    // ===== or =====
    .ElementAttr(new Dictionary<string, object>() {
        { "id", "elementId" },
        { "class", "class-name" }
    })

)

@(Html.DevExtreme().WidgetName() _
    .ElementAttr("class", "class-name")
    ' ===== or =====
    .ElementAttr(New With {
        .id = "elementId",
        .class = "class-name"
    })
    ' ===== or =====
    .ElementAttr(New Dictionary(Of String, Object) From {
        { "id", "elementId" },
        { "class", "class-name" }
    })
)

View Demo

See Also

• Customize Item Appearance
• Custom Templates

If this option is set to 'true', the object assigned to the items option should include key and items properties. The key property specifies the group caption in the list. The items property represents an array listing group items.

View Demo

See Also

• Enable Grouping
• Custom Templates

This option accepts a value of one of the following types:

• Number
  The height in pixels.

• String
  A CSS-accepted measurement of height. For example, "55px", "80%", "auto", "inherit".

• Function
  A function returning either of the above. For example:

  JavaScript

  height: function() {
      return window.innerHeight / 1.5;
  }

You can configure this option in an ASP.NET MVC Control as follows:

@(Html.DevExtreme().WidgetName()
    .InputAttr("id", "inputId")
    // ===== or =====
    .InputAttr(new {
        @id = "inputId"
    })
    // ===== or =====
    .InputAttr(new Dictionary<string, object>() {
        { "id", "inputId" }
    })
)

@(Html.DevExtreme().WidgetName() _
    .InputAttr("id", "inputId")
    ' ===== or =====
    .InputAttr(New With {
        .id = "inputId"
    })
    ' ===== or =====
    .InputAttr(New Dictionary(Of String, Object) From {
        { "id", "inputId" }
    })
)

In Knockout apps, you may need to inform a user about an error that occurred during the validation of a view model field. For this purpose, set the editor's isValid option to the isValid value of the dxValidator that validates this field. To show an error message, set the editor's validationError option to the dxValidator's validationError value.

var editorValue = ko.observable("").extend({
    dxValidator: {
        validationRules: [{
            type: 'required',
            message: 'Specify this value'
        }]
    }
});
var viewModel = {
    editorOptions: {
        value: editorValue,
        isValid: editorValue.dxValidator.isValid,
        validationError: editorValue.dxValidator.validationError
    }
};

The editor's isValid and validationError options should also be specified when using a custom validation engine. In this instance, the validation result will be displayed for the editor by the means of the DevExtreme Validation UI.

See Also

• Knockout Only - Validate a View Model
• Use a Custom Validation Engine

You can use the dataSource option instead. Unlike the items option, the dataSource option can take on the DataSource configuration object as well as a simple array.

View Demo

See Also

• Customize Item Appearance
• Custom Templates

Specify this option if the widget lies within an HTML form that will be submitted.

If you configure the widget as an ASP.NET MVC Control, use this option to bind the widget to a model property. If this model property contains Data Annotation validation attributes, you get the client-side validation enabled by default.

Assign a function to perform a custom action after a drop-down editor has been hidden.

If data displayed by the widget is specified using a DataSource instance, the contentReady event fires each time the load() method of the DataSource instance is called as well as when widget content is ready. In this case, when you create the widget, the contentReady event is raised twice: when the widget's content is ready (at this moment, the widget does not display items) and when the DataSource is loaded (the widget displays the loaded items).

You cannot access widget elements in this handler because it is executed before they are ready. Use the onContentReady handler instead.

Assign a function to perform a custom action when a widget item is clicked.

To navigate to a specific URL when the itemClick event fires, assign that URL directly to this option.

Assign a function to perform a custom action when the drop-down editor is shown.

Assign a function to perform a custom action before loading the next page in the lookup list if auto-paging is enabled.

Assign a function to perform a custom action before the lookup list is refreshed as a result of the "pull down to refresh" gesture.

Assign a function to perform a custom action on each scroll gesture.

Assign a function to perform a custom action when the selection changes.

Assign a function to perform a custom action after a collection item title is rendered.

Assign a function to perform a custom action when the editor value changes.

Use the selectedItem field of the argument object passed to the onSelectionChanged event handler to access selected item.

View Demo

When using the widget as an ASP.NET MVC Control, specify this option using the ListPageLoadMode enum. This enum accepts the following values: ScrollBottom and NextButton.

This option accepts a value of one of the following types:

• Number
  The height in pixels.

• String
  A CSS-accepted measurement of height. For example, "55px", "80%", "auto", "inherit".

• Function
  A function returning either of the above. For example:

  JavaScript

  height: function() {
      return window.innerHeight / 1.5;
  }

This option accepts a value of one of the following types:

• Number
  The width in pixels.

• String
  A CSS-accepted measurement of width. For example, "55px", "80%", "auto", "inherit".

• Function
  A function returning either of the above. For example:

  JavaScript

  width: function() {
      return window.innerWidth / 1.5;
  }

If the option is set to true, the widget data is refreshed each time you pull down and release widget contents.

When this option is set to true, the widget text flows from right to left, and the layout of elements is reversed. To switch the entire application/site to the right-to-left representation, assign true to the rtlEnabled field of the object passed to the DevExpress.config(config) method.

DevExpress.config({
    rtlEnabled: true
});

See Also

• Right-to-Left Support Demo: DataGrid | Navigation Widgets | Editors

See Also

• Configure Search Parameters

In most cases, you should pass the name of a field by whose value data items are searched. If you need to search elements by several field values, assign an array of field names to this option.

searchExpr: ["firstName", "lastName"]

For more information on searching, refer to the Search API section of the Data Layer article. For information on getters, refer to the Getters and Setters section of the Data Layer article.

When using the widget as an ASP.NET MVC Control, specify this option using the DropDownSearchMode enum. This enum accepts the following values: Contains and StartsWith.

The Cancel button cancels the attempt to change the lookup widget value.

The Clear button clears the currently chosen lookup value. The lookup window closes and the text specified by the placeholder option is shown in the lookup editor.

If this option is disabled, the widget does not display values until the number of typed characters exceeds the minSearchLength value, otherwise it displays all values regardless of the specified filtering condition.

The value of this option will be passed to the tabindex attribute of the HTML element that underlies the widget.

See Also

• Customize the Drop-Down Menu
• Custom Templates

The Lookup widget can display its contents in a Popover widget only if the fullScreen mode is disabled. Otherwise, lookup contents are displayed within the Popup widget.

See Also

• Use a Custom Validation Engine

The following option values are possible:

• auto
  The tooltip with the message is displayed when the editor is in focus.
• always
  The tooltip with the message is not hidden when the editor loses focus.

When using the widget as an ASP.NET MVC Control, specify this option using the ValidationMessageMode enum. This enum accepts the following values: Auto and Always.

This option accepts a value of one of the following types:

• Number
  The width in pixels.

• String
  A CSS-accepted measurement of width. For example, "55px", "80%", "auto", "inherit".

• Function
  A function returning either of the above. For example:

  JavaScript

  width: function() {
      return window.innerWidth / 1.5;
  }