Getting Started with the Filter

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

Sample Telerik UI for ASP.NET Core Filter

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, paragraphs, and others.

@using Kendo.Mvc
<h4>Telerik UI Filter Component</h4>
<p>
</p>

@addTagHelper *, Kendo.Mvc
<h4>Filter with event handler</h4>
<p>
</p>

2. Initialize the Filter

Use the Calendar 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 Filter element.
The MainLogic() configuration method defines the value of the logical operator at the root level of the filter expression.
The ApplyButton will display a button which when clicked will apply filtering over the datasource.
The Fields is an array of JavaScript objects that hold information about the filter field, it's editor, default values used for filter and etc.
The FilterExpression is An object which represents a filter expression which the kendo.data.DataSource can use to filter the data.

@using Kendo.Mvc
<h4>Telerik UI Filter Component</h4>
<p>
@(Html.Kendo().DataSource<TelerikAspNetCoreApp1.Models.Sushi>()
        .Name("dataSource1")
        .Custom(c => c.Transport(transport =>
        {
            transport.Read(read =>
               read.Url("https://demos.telerik.com/kendo-ui/content/spa/websushi/menu.json")
                   .DataType("json")
            );
        })
        .PageSize(4))
    )

@(Html.Kendo().Filter<TelerikAspNetCoreApp1.Models.Sushi>()
        .Name("filter")
        .MainLogic(FilterCompositionLogicalOperator.Or)
        .ApplyButton()
        .Fields(f =>
        {
            f.Add(p => p.name).Label("Name");
            f.Add(p => p.price).Label("Price");
            f.Add(p => p.description).Label("Description");
        })
        .FilterExpression(f =>
        {
            f.Add(p => p.price).IsGreaterThanOrEqualTo(5);
            f.Add(p => p.name).Contains("Salad");
        })
        .DataSource("dataSource1")
    )
</p>

@addTagHelper *, Kendo.Mvc
<h4>Telerik UI Filter Component</h4>
<p>
    <kendo-datasource name="dataSource1" type="DataSourceTagHelperType.Custom" page-size="4">
        <transport>
            <read url="https://demos.telerik.com/kendo-ui/content/spa/websushi/menu.json")" datatype="json" />
        </transport>
    </kendo-datasource>

    <kendo-filter apply-button="true"  main-logic="Or" name="filter" expression="InitialExpression" datasource-id="dataSource1">
        <fields>
            <filter-field name="name" type="string" label="Name">
            </filter-field>
            <filter-field name="price" type="number" label="Price">
            </filter-field>
            <filter-field name="description" type="string" label="Description">
            </filter-field>
        </fields>
    </kendo-filter>
</p>

3. Enable The Preview of the Expression

The next step is to configure the Filter to visualize the filter expression that will be applied to the datasource.

@using Kendo.Mvc

<h4>Telerik UI Filter Component</h4>
<p>
    @(Html.Kendo().DataSource<TelerikAspNetCoreApp1.Models.Sushi>()
        .Name("dataSource1")
        .Custom(c => c.Transport(transport =>
        {
            transport.Read(read =>
            read.Url("https://demos.telerik.com/kendo-ui/content/spa/websushi/menu.json")
            .DataType("json")
            );
        })
        .PageSize(4))
    )

    @(Html.Kendo().Filter<TelerikAspNetCoreApp1.Models.Sushi>()
        .Name("filter")
        .MainLogic(FilterCompositionLogicalOperator.Or)
        .ApplyButton()
        .ExpressionPreview()
        .Fields(f =>
        {
            f.Add(p => p.name).Label("Name");
            f.Add(p => p.price).Label("Price");
            f.Add(p => p.description).Label("Description");
        })
        .FilterExpression(f =>
        {
            f.Add(p => p.price).IsGreaterThanOrEqualTo(5);
            f.Add(p => p.name).Contains("Salad");
        })
        .DataSource("dataSource1")
     )
</p>

@addTagHelper *, Kendo.Mvc
<h4>Calendar with event handler</h4>
<p>
    <kendo-datasource name="dataSource1" type="DataSourceTagHelperType.Custom" page-size="4">
        <transport>
            <read url="https://demos.telerik.com/kendo-ui/content/spa/websushi/menu.json")" datatype="json" />
        </transport>
    </kendo-datasource>

    <kendo-filter apply-button="true" expression-preview="true" main-logic="Or" name="filter" expression="InitialExpression" datasource-id="dataSource1">
        <fields>
            <filter-field name="name" type="string" label="Name">
            </filter-field>
            <filter-field name="price" type="number" label="Price">
            </filter-field>
            <filter-field name="description" type="string" label="Description">
            </filter-field>
        </fields>
    </kendo-filter>
</p>

The Filter exposes a Change() event that you can handle and assign specific functions to the component. In this tutorial, you will use the Change() event to display a message when the user modifies the Filter.

@using Kendo.Mvc.UI
<script>
    function onChange(){
        console.log("change");
    }
</script>
<h4>Filter with event handler</h4>
<p>
    @(Html.Kendo().DataSource<Kendo.Mvc.Examples.Models.Sushi>()
        .Name("dataSource1")
        .Custom(c => c.Transport(transport =>
        {
            transport.Read(read =>
               read.Url("https://demos.telerik.com/kendo-ui/content/spa/websushi/menu.json")
                   .DataType("json")
            );
        })
        .PageSize(4))
    )

    @(Html.Kendo().Filter<Kendo.Mvc.Examples.Models.Sushi>()
        .Name("filter")
        .MainLogic(FilterCompositionLogicalOperator.Or)
        .ApplyButton()
        .ExpressionPreview()
        .Fields(f =>
        {
            f.Add(p => p.name).Label("Name");
            f.Add(p => p.price).Label("Price");
            f.Add(p => p.description).Label("Description");
        })
        .FilterExpression(f =>
        {
            f.Add(p => p.price).IsGreaterThanOrEqualTo(5);
            f.Add(p => p.name).Contains("Salad");
        })
        .Events(e => e.Change("onChange"))
        .DataSource("dataSource1")
    )
</p>

@addTagHelper *, Kendo.Mvc
<script>
    function onChange(){
        console.log("change");
    }
</script>
<h4>Filter with event handler</h4>
<p>
    <kendo-datasource name="dataSource1" type="DataSourceTagHelperType.Custom" page-size="4">
        <transport>
            <read url="https://demos.telerik.com/kendo-ui/content/spa/websushi/menu.json")" datatype="json" />
        </transport>
    </kendo-datasource>

    <kendo-filter apply-button="true" expression-preview="true" main-logic="Or" name="filter" expression="InitialExpression" datasource-id="dataSource1" on-change="onChange">
        <fields>
            <filter-field name="name" type="string" label="Name">
            </filter-field>
            <filter-field name="price" type="number" label="Price">
            </filter-field>
            <filter-field name="description" type="string" label="Description">
            </filter-field>
        </fields>
    </kendo-filter>
</p>

5. (Optional) Reference Existing Calendar Instances

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

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

<script>
    var filterInstance = $("#filter").data("kendoFilter"); // filterInstance is a reference to the existing Filter instance of the helper.
</script>

Use the Filter client-side API to control the behavior of the widget. In this example, you will use the applyFilter method to apply the generated filter to the dataSource. script <script> var filterInstance = $("#filter").data("kendoFilter"); // filterInstance is a reference to the existing Filter instance of the helper. filterInstance.applyFilter(); </script> For more information on referencing specific helper instances, see the Methods and Events article.

Explore this Tutorial in REPL

You can continue experimenting with the code sample above by running it in the Telerik REPL server playground:

Getting Started with the Filter

Prerequisites

1. Prepare the CSHTML File

2. Initialize the Filter

3. Enable The Preview of the Expression

4. Handle a Filter Event

5. (Optional) Reference Existing Calendar Instances

Explore this Tutorial in REPL

Next Steps

Getting Started

Support Resources

Community