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title page_title description slug tags published position
Overview
DropDownList Overview
The Blazor DropDownList allows users to select an option from a list, enabling dynamic data binding and event handling in web apps.
components/dropdownlist/overview
telerik,blazor,dropdownlist,dropdown,list,overview
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0

Blazor DropDownList Overview

The Blazor DropDownList component allows the user to choose an option from a predefined set of choices presented in a dropdown list popup. The developer can control the data, sizes, and various appearance options like class and templates.

Creating Blazor DropDownList

  1. Use the TelerikDropDownList tag to add the Blazor dropdown list to your razor page.
  2. Populate its Data property with the collection of items you want to appear in the dropdown list.
  3. Set the TextField and ValueField properties to point to the corresponding names of the model.
  4. Bind the value of the component to a variable of the same type as the type defined in the ValueField parameter.
  5. (optional) Set the Value property to the initial value of the model.

caption DropDownList data binding, two-way value binding, and main features

Selected value: @selectedValue
<br />

<TelerikDropDownList Data="@myDdlData" TextField="MyTextField" ValueField="MyValueField" @bind-Value="selectedValue">
</TelerikDropDownList>

@code {
    //in a real case, the model is usually in a separate file
    //the model type and value field type must be provided to the dropdpownlist
    public class MyDdlModel
    {
        public int MyValueField { get; set; }
        public string MyTextField { get; set; }
    }

    int selectedValue { get; set; } = 3;

    IEnumerable<MyDdlModel> myDdlData = Enumerable.Range(1, 20).Select(x => new MyDdlModel { MyTextField = "item " + x, MyValueField = x });
}

caption The rendered DropDownList component from the code snippet above:

Blazor DropDown List component

Data Binding

The Blazor DropDownList @template Read more about the Blazor DropDownList data binding....

Filtering

The Blazor DropDownList @template Read more about the Blazor DropDownList filter....

Grouping

The Blazor DropDownList @template Read more about the Blazor DropDownList grouping....

Templates

@template Read more about the Blazor DropDownList templates....

Validation

@template

Virtualization

@template Read more about the Blazor DropDownList virtualization...

Adaptive Rendering

@template

DropDownList Parameters

caption The Blazor dropdown list provides various parameters that allow you to configure the component:

@template

Parameter Type Description
AdaptiveMode AdaptiveMode
(None)		 The adaptive mode of the component.
Data IEnumerable<TItem> Allows you to provide the data source. Required.
DefaultText string Simple hint to be displayed when no item is selected yet. In order for it to be shown, the Value parameter should be set to a default value depending on the type defined in the ValueField parameter. For example, 0 for an int, and null for an int? or string. You need to make sure that it does not match the value of an existing item in the data source. See the first example in the Examples section in this article and in the Input Validation article.
Enabled bool Whether the component is enabled.
ReadOnly bool If set to true, the component will be readonly and will not allow user input. The component is not readonly by default and allows user input.
Filterable bool Whether filtering is enabled for the end user.
FilterDebounceDelay int
150		 Time in milliseconds between the last typed symbol and the filter input value update. Applicable to filtering only. Use it to balance between client-side performance and number of database queries.
FilterOperator StringFilterOperator
(StartsWith)		 The method of filtering the items.
FilterPlaceholder string The hint that will be displayed in the filter input when it has no value.
Id string The id attribute rendered on the main wrapping element of the component (<span class="k-dropdownlist">). You can use it to attach a <label for=""> to it.
InputMode string The inputmode attribute of the <input /> element.
TItem Type The type of the model to which the component is bound. Required if you can't provide Data or Value. Determines the type of the reference object.
TValue Type The type of the value field from the model to which the component is bound. Required if you can't provide Data or Value. Determines the type of the reference object. The type of the values can be:
- number (such as int, double, and so on)
- string
- Guid
- Enum
Title string The title text rendered in the header of the dropdown list popup (action sheet). Applicable only when AdaptiveMode is set to Auto.
TabIndex int? The tabindex attribute rendered on the dropdown list.
TextField string
(Text)		 The name of the field from the model that will be shown to the user.
ValueField string
(Value)		 The name of the field from the model that will be the underlying value.
Value and bind-Value TValue Gets/sets the value of the component, can be used for binding. If you set it to a value allowed by the model class value field, the corresponding item from the data collection will be pre-selected. Use the bind-Value syntax for two-way binding, for example, to a variable of your own.

Styling and Appearance

The following parameters enable you to customize the appearance of the Blazor DropDownList component:

@template

tip To learn more about the appearance, anatomy, and accessibility of the DropDownList, visit the Progress Design System Kit documentation—an information portal offering rich component usage guidelines, descriptions of the available style variables, and globalization support details.

Popup Settings

The DropDownList exposes settings for its dropdown (popup). To configure the options, declare a <DropDownListPopupSettings> tag inside a <DropDownListSettings> tag:

<TelerikDropDownList Data="@DropDownData"
                     @bind-Value="@SelectedItem"
                     Filterable="true"
                     FilterOperator="@StringFilterOperator.Contains"
                     FilterPlaceholder="Filter by digit or letter"
                     Width="240px">
    <DropDownListSettings>
        <DropDownListPopupSettings Height="auto" MaxHeight="200px" MinHeight="75px" />
    </DropDownListSettings>
</TelerikDropDownList>

@code {
    private List<string> DropDownData { get; set; } = Enumerable.Range(1, 50)
        .Select(x => { return $"Item {x} {(char)Random.Shared.Next(65, 91)}{(char)Random.Shared.Next(65, 91)}"; })
        .ToList();

    private string SelectedItem { get; set; }
}

The DropDownList provides the following popup settings:

@template

DropDownList Reference and Methods

The DropDownList is a generic component and its type comes from the model it is bound to and from the value field type. See the Component Reference section in the Data Binding article for details and examples.

Add a reference to the component instance to use the DropDownList's methods.

@template

<TelerikDropDownList @ref="@DropDownListRef"
                     Data="@DropDownListData"
                     @bind-Value="@DropDownListValue"
                     Width="300px" />

<TelerikButton OnClick="@OpenPopup">Open Popup</TelerikButton>

@code {
    private TelerikDropDownList<string, string> DropDownListRef { get; set; }

    private string DropDownListValue { get; set; }

    private List<string> DropDownListData { get; set; } = new List<string> { "first", "second", "third" };

    private void OpenPopup()
    {
        DropDownListRef.Open();
        
        DropDownListValue = DropDownListData.First();

        DropDownListRef.Refresh();
    }
}

Selected Item and DefaultText

By default, if no Value is provided and no DefaultText is defined, the DropDownList will appear empty.

  • To display DefaultText - Value should be 0 or null depending on the data type you are using in the ValueField and the DefaultText should be defined.

  • To display a selected item when the component renders - provide the Value of the desired element. Note that it must match an item of the component's data source.

Examples

caption Default text (hint) to show when no actual item is selected

@MyStringItem
<TelerikDropDownList Data="@MyStringList" @bind-Value="@MyStringItem" DefaultText="Select something">
</TelerikDropDownList>

<br />
<br />

@MyIntItem
<TelerikDropDownList Data="@MyIntList" @bind-Value="@MyIntItem" DefaultText="Select another thing">
</TelerikDropDownList>

@code {
    protected List<string> MyStringList = new List<string>() { "first", "second", "third" };

    //Current value is null (no item is sellected) which allows the DefaultText to be displayed.
    protected string MyStringItem { get; set; }

    protected List<int> MyIntList = new List<int>() { 1, 2, 3 };

    //Current value is 0 (no item is sellected) which allows the DefaultText to be displayed.
    protected int MyIntItem { get; set; }
}

caption Get selected item from external code

@result
<br />

<TelerikDropDownList Data="@myDdlData" TextField="MyTextField" ValueField="MyValueField"
                     @bind-Value="@DdlValue" DefaultText="Select something">
</TelerikDropDownList>

<TelerikButton OnClick="@GetSelectedItem">Get Selected Item</TelerikButton>

@code {
    string result;
    int DdlValue { get; set; } = 5;
    void GetSelectedItem()
    {
        // extract the data item from the data source by using the value
        MyDdlModel selectedItem = myDdlData.Where(d => d.MyValueField == DdlValue).FirstOrDefault();
        if (selectedItem != null)
        {
            result = selectedItem.MyTextField;
        }
        else
        {
            result = "no item selected";
        }

        StateHasChanged();
    }

    public class MyDdlModel
    {
        public int MyValueField { get; set; }
        public string MyTextField { get; set; }
    }

    IEnumerable<MyDdlModel> myDdlData = Enumerable.Range(1, 20).Select(x => new MyDdlModel { MyTextField = "item " + x, MyValueField = x });
}

@template

Next Steps

  • Binding the DropDownList to Data
  • Pre-Selecting Items for the User

See Also