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Fundamentals

Telerik UI for ASP.NET Core is a set of server-side wrappers (HTML and tag helpers) that allow you to use the Kendo UI widgets in .NET Core.

For more information on the difference between helpers and widgets, refer to the Telerik UI for ASP.NET Core introduction article.

As of the jQuery 3.0 release, the document-ready handlers are called asynchronously. As a result, regardless of whether the document is ready at the point of execution or not, the code placed outside a document-ready handler is executed before the code within the handler. This change affects the usage of the Telerik UI for ASP.NET Core components because the widgets for the MVC helpers are initialized in a document-ready handler. This means that after the jQuery 3.0 release you need to get the reference of a widget and its API calls within a document-ready handler.

Basic Configuration

HTML Helpers

The HTML Helper options are exposed through a fluent interface.

UI for ASP.NET Core Applying the fluent interface

To set an option for a helper, call the corresponding method and pass the required option value.

@(Html.Kendo().NumericTextBox()
      .Name("name") // Set the name of the NumericTextBox.
      .Value(10) // Set the value.
      .Spinners(false) // Disable the spinners.
)

You have to set the Name option of the helper. The value will be used as the id and name HTML attributes—the name attribute is set only for input helpers such as the DatePicker, NumericTextBox, and DropDownList. The id attribute is used to initialize the helper. The id (Name) of a helper has to meet the requirements for valid HTML ID attributes. It must not contain spaces and special characters and has to start with a letter.

The Name options of the helpers have to be always unique in the context of the whole web page. If a partial view is loaded multiple times, each instance of this partial view has to render all helpers with unique Name (id) options. If this requirement is not met, the page will render duplicate element IDs and only the helper instance which occurs first in the markup will be initialized and will work properly.

UI for ASP.NET Core A sample server-side wrapper name

Alternatively, you can use the NumericTextBoxFor setting. All Telerik UI helpers which accept a value can be initialized with the [WidgetName]For method. For example, to initialize the DatePicker, use DatePickerFor. These methods automatically set the Name of the helper. In this way, @Html.Kendo().NumericTextBoxFor(model => model.Age) is the same as @Html.Kendo().NumericTextBox().Name("Age").Value(Model.Age).

Tag Helpers

You can configure the Tag Helpers through the predefined strongly typed attributes which also provide IntelliSense. Complex and composite properties, as well as nested configuration tags, are not supported.

UI for ASP.NET Core Applying the TagHelper IntelliSense

To configure an ASP.NET Core project that enables you to use a Telerik UI Tag Helper, add the @addTagHelper directive to your cshtml file. Also, you can globally add the directive in Views/_ViewImports.cshtml.

    @addTagHelper "*, Kendo.Mvc"

Add the desired options as attributes and set their value.

    <kendo-numerictextbox name="currency" //Ensure that the attribute `name` is unique in the context of the whole web page.
        format="c" min="0" spinners="false" enable="true" max="100" value="10">
    </kendo-numerictextbox>

When binding a Tag Helper editor to a Model property, use the attribute for. It will automatically set the name attribute to the name of the Model property.

    <kendo-numerictextbox for="currency" format="c" min="0" spinners="false" max="200">
    </kendo-numerictextbox>

Deferred Initialization

By default, the helpers output the widget initialization script immediately after the HTML markup of the widget. This scenario may not always be desired—for example, if the script files are registered at the bottom of the page or when you nest widgets.

To defer the initialization:

  1. Call the Deferred method of the HTML helper or enable the deferred option of the Tag helper. This approach suppresses the immediate rendering of the script statement.

        @(Html.Kendo().NumericTextBox()
            .Name("age")
            .Deferred()
        )
    
        <kendo-numerictextbox name="age" deferred="true">
        </kendo-numerictextbox>
    
  2. Call the DeferredScripts method. As a result, all previously deferred initialization statements are output.

      @Html.Kendo().DeferredScripts()
    

    The DeferredScripts method accepts a Boolean parameter which determines whether script elements will be automatically rendered. This behavior is useful for rendering the deferred initialization scripts inside existing script element.

        <script>
            @Html.Kendo().DeferredScripts(false)
        </script>
    
  3. Render the deferred initialization script of a particular helper by using the DeferredScriptsFor method.

    @(Html.Kendo().NumericTextBox()
        .Name("age")
        .Deferred()
    )

    <!-- other code -->
    @Html.Kendo().DeferredScriptsFor("age")
    <kendo-numerictextbox name="age" deferred="true">
    </kendo-numerictextbox>

    <!-- other code -->
    @Html.Kendo().DeferredScriptsFor("age")

You can also use the DeferredScriptsFor method to suppress the output of script elements around the initialization script.

    <script>
    @Html.Kendo().DeferredScriptsFor("age", false)
    </script>

Referencing Client-Side Objects

You can get a reference to the client-side object that is initialized by the helper through the data jQuery method. Use the Name of the widget in an ID jQuery selector, and obtain the reference in a document.ready handler which is placed or called after the widget is declared. This ensures that the widget is already initialized and the client-side object exists. After you get the object reference, use the client-side API of the widget.

    @(Html.Kendo().NumericTextBox()
        .Name("age")
    )
    <kendo-numerictextbox name="age" value="10">
    </kendo-numerictextbox>
    $(function(){
        var numeric = $("#age").data("kendoNumericTextBox");
        numeric.value(10);
    });

If you have deferred the initialization of the widget, make sure you get its instance after calling DeferredScripts or DeferredScriptsFor.

    @(Html.Kendo().NumericTextBox()
        .Name("age")
        .Deferred()
    )

    .....

    @Html.Kendo().DeferredScripts()
    <kendo-numerictextbox name="age" deferred="true">
    </kendo-numerictextbox>

    .....

    @Html.Kendo().DeferredScripts()
    $(function(){
        var numeric = $("#age").data("kendoNumericTextBox");
        numeric.value(10);
    });

Using Client Templates

HTML Helpers

By default, every Telerik UI helper renders a script element with an initialization statement. If the helper declaration is placed inside a Kendo UI template, the nested script elements will be invalid. The ToClientTemplate method instructs the helper to escape its own script element so that it can be nested.

<script id="template" type="text/x-kendo-template">
    @(Html.Kendo().NumericTextBox()
          .Name("age")
          .ToClientTemplate()
    )
</script>
<div id="container"></div>
<script>
    $(function () {
       var template = kendo.template($("#template").html());
       $("#container").append( template ({}) );
    })
</script>

Tag Helpers

Тhe .NET framework ignores any Tag Helpers which are within script tags. In order to compile them correctly, when placing a Tag Helper within a Kendo Template, set the type to text/html and add the is-in-client-template="true" attribute.

The following example demonstrates how to include Chart TagHelpers in the TileLayout TagHelper.

    <!-- container chart templates -->
    <script id="downloads-template" type="text/html">
        <kendo-chart name="downloads" is-in-client-template="true">
            <series>
                <series-item type="ChartSeriesType.Line" data="new double[] { 56000, 63000, 74000, 91000, 117000, 138000 }">
                </series-item>
            </series>
        </kendo-chart>
    </script>
    <script id="devices-template" type="text/html">
        <kendo-chart name="devices" is-in-client-template="true">
            <series>
                <series-item type="ChartSeriesType.Donut" auto-fit="true" data='new dynamic[] {
                    new {category = "Asia",value = 30.8,color = "\\#006634"},
                    new {category = "Europe",value = 69.2,color = "\\#90cc38"}}'>
                </series-item>
            </series>
        </kendo-chart>
    </script>
    <kendo-tilelayout name="tilelayout" columns="2" resizable="true" reorderable="true">
        <containers>
            <container body-template-id="downloads-template" col-span="1" row-span="1">
                <container-header text="Weekly Recap-Downloads" />
            </container>
            <container body-template-id="devices-template" col-span="1" row-span="1">
                <container-header text="Devices" />
            </container>
        </containers>
    </kendo-tilelayout>

See Also

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