Getting Started with the CheckBox

This tutorial explains how to set up a basic Telerik UI for ASP.NET Core CheckBox and highlights the major steps in the configuration of the component.

You will initialize a CheckBox component with explicitly defined messages depending on its check state, and then change its appearance. Finally, you will learn how to handle the events of the CheckBox.

Sample Telerik UI for ASP.NET Core CheckBox

Prerequisites

To successfully complete the tutorial, you need a project that is already configured to use the Telerik UI for ASP.NET Core components:

You can use the Telerik REPL playground and skip installing the components on your system and configuring a project.
You can prepare a Visual Studio project by following either of these guides:
- Creating a new pre-configured project for the Telerik UI for ASP.NET Core components from a project template.
- Manually configuring an existing project as described in the First Steps on Windows or First Steps on Mac articles.

1. Prepare the CSHTML File

The first step is to add the required directives at the top of the .cshtml document:

To use the Telerik UI for ASP.NET Core HtmlHelpers:
```
@using Kendo.Mvc.UI
```
To use the Telerik UI for ASP.NET Core TagHelpers:
```
@addTagHelper *, Kendo.Mvc
```

Optionally, you can structure the document by adding the desired HTML elements like headings, divs, and paragraphs.

    @using Kendo.Mvc.UI
    <h4>CheckBox with a placeholder</h4>
    <div>

    </div>

    @addTagHelper *, Kendo.Mvc
    <h4>CheckBox with a placeholder</h4>
    <div>

    </div>

2. Initialize the CheckBox

Use the CheckBox HtmlHelper or TagHelper to add the component to a page:

The Name() configuration method is mandatory as its value is used for the id and the name attributes of the CheckBox element.

    @(Html.Kendo().CheckBox()
        .Name("checkbox")    
    )

    <kendo-checkbox name="checkbox">
    </kendo-checkbox>

3. Configure the Label

The next step is to explicitly define the label for the CheckBox. The following example will configure the label functionality.

    @(Html.Kendo().CheckBox()
        .Name("checkbox")    
        .Label("My Telerik Checkbox")
    )

    <kendo-checkbox name="checkbox"
                label="My Telerik Checkbox">
    </kendo-checkbox>

4. Customize the Appearance of the CheckBox

To change the appearance of the CheckBox, use any of its built-in styling options, for example, Size() or Rounded().

    @(Html.Kendo().CheckBox()
        .Name("checkbox")
        .Label("My Telerik Checkbox")
        .Size(ComponentSize.Medium)
        .Rounded(BasicRounded.Medium)
    )

    <kendo-checkbox name="checkbox"
                    label="My Telerik Checkbox"
                    size="ComponentSize.Medium"
                    rounded="Rounded.Medium">
    </kendo-checkbox>

5. Handle the CheckBox Events

The CheckBox component exposes an event that you can handle and further customize the functionality of the component. In this tutorial, you will use the Change event to display a popup message when the value of the CheckBox changes through user interaction.

    @(Html.Kendo().CheckBox()
        .Name("checkbox")
        .Label("My Telerik Checkbox")
        .Size(ComponentSize.Medium)
        .Rounded(BasicRounded.Medium)
        .Events(events => events.Change("onChange"))
    )

    <script>
        function onChange(e){
            alert("Changed value: "+ e.sender.value());
        }
    </script>

    <kendo-checkbox name="checkbox"
                    label="My Telerik Checkbox"
                    size="ComponentSize.Medium"
                    rounded="Rounded.Medium"
                    on-change="onChange">
    </kendo-checkbox>

    <script>
        function onChange(e){
            alert("Changed value: "+ e.sender.value());
        }
    </script>

6. (Optional) Reference Existing CheckBox Instances

You can reference the CheckBox instances that you have created and build on top of their existing configuration:

Use the .Name() (id attribute) of the component instance to get a reference.

     <script>
         $(document).ready(function() {
             var checkBoxReference = $("#checkbox").data("kendoCheckBox"); // checkBoxReference is a reference to the existing CheckBox instance of the helper.
         })
     </script>

Set the check state of the component by using the check() client-side method.

    <script>
        $(document).ready(function() {
           var checkBoxReference = $("#checkbox").data("kendoCheckBox"); // checkBoxReference is a reference to the existing CheckBox instance of the helper.
           checkBoxReference.check(true); // Set the initial check state of the component.
        })
    </script>