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.

This option accepts one of the following:

• Array
  A JavaScript array that contains string, numeric, Boolean values, or plain objects.

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

• DataSource or its configuration object
  The DataSource is an object that provides an API for data processing. The DataSource's underlying data access logic is isolated in a store. Refer to the Data Layer and DataSource Examples guides for more information about the DataSource.

If the data source contains objects, specify the key in the store and/or a data field providing values in the widget.

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.

See Also

• key in ArrayStore | CustomStore | LocalStore | ODataStore

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.

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" }
    })
)

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;
  }

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.

See Also

• Customize Item Appearance
• Custom Templates

The following values are available.

• 'vertical'
  Radio buttons are arranged vertically - as a column.

• 'horizontal'
  Radio buttons are arranged horizontally - as a row.

When using the widget as an ASP.NET MVC Control, specify this option using the Orientation enum. This enum accepts the following values: Horizontal and Vertical.

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.

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 the editor value changes.

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

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