TextArea

Multi-line text that can grow and count.

An interactive page: C# runs over a Blazor Server connection.

Usage

razor

@* Label, required mark and limits from the model. *@
<TextArea @bind-Value="Model!.Description" />

@* A short bio that grows and counts toward its [StringLength]. *@
<TextArea @bind-Value="Model!.Bio" Rows="2" AutoGrow ShowCount
          Hint="Up to 160 characters, shown on your profile." />

A text area takes its label, hint, required mark and limits from the model, as a TextField does. Use a text field for one line, such as a name or a title.

Rows and placeholder

Use Rows for how many lines show (4 by default); longer text scrolls, and people can drag the corner to make it taller.

Preview Code

Preview

Code

Rows.razor

<Form Model="Model" FormName="text-area-rows" MaxWidth="28.Rem" Grow>
    <TextArea @bind-Value="Model!.Notes" Rows="6" Placeholder="Steps to reproduce, what you expected, what happened" />
</Form>

@code {
    [SupplyParameterFromForm(FormName = "text-area-rows")]
    private BugReport? Model { get; set; }

    protected override void OnInitialized() => Model ??= new();

    public sealed class BugReport
    {
        public string? Notes { get; set; }
    }
}

A placeholder disappears as people type, so keep anything they need while writing in the Hint.

Growing, with a count

Use AutoGrow to grow with the text from Rows up, and ShowCount to show "n / max" under the field, against the limit from [StringLength], [MaxLength] or MaxLength.

Preview Code

Preview

Code

Count.razor

@using System.ComponentModel.DataAnnotations

<Form Model="Model" FormName="text-area-count" MaxWidth="28.Rem" Grow>
    <TextArea @bind-Value="Model!.Bio" Rows="2" AutoGrow ShowCount Hint="Shown on your public profile." />
</Form>

@code {
    [SupplyParameterFromForm(FormName = "text-area-count")]
    private Profile? Model { get; set; }

    protected override void OnInitialized() => Model ??= new();

    public sealed class Profile
    {
        [StringLength(160)]
        public string? Bio { get; set; } = "Designer at Acme. I draw interfaces, then delete half of them.";
    }
}

Growing is CSS (field-sizing), so it works with JavaScript off in browsers that support it; others keep the scroll bar and the corner to drag. The count needs a limit, and the browser stops typing at it.

Required, with a length

Use [Required] and [StringLength] with a MinimumLength for the rules, and their ErrorMessage for the words the browser and the server show.

Preview Code

Preview

Code

Feedback.razor

@using System.ComponentModel.DataAnnotations

<Form Model="Model" FormName="text-area-feedback" OnValidSubmit="Send" MaxWidth="28.Rem" Grow>
    <TextArea @bind-Value="Model!.Message" Label="What could be better?" Rows="3" AutoGrow ShowCount
              Hint="20 to 500 characters." />
    <Row><Button Submit>Send feedback</Button></Row>
    @if (_sent is not null)
    {
        <Alert Status="Status.Success">Thanks: we got your @_sent.Length characters.</Alert>
    }
</Form>

@code {
    [SupplyParameterFromForm(FormName = "text-area-feedback")]
    private Suggestion? Model { get; set; }

    // What was sent, not the field: on an interactive page the field follows typing.
    private string? _sent;

    protected override void OnInitialized() => Model ??= new();

    private void Send() => _sent = Model!.Message;

    public sealed class Suggestion
    {
        [Required(ErrorMessage = "Tell us what could be better.")]
        [StringLength(500, MinimumLength = 20, ErrorMessage = "Write 20 to 500 characters.")]
        public string? Message { get; set; }
    }
}

Live: The browser checks in the model's words, as on static pages, and Send runs C# without a page load.

The browser checks the minimum only on text someone has typed, so the validator's check after posting is the one to rely on; it also catches text that arrives too long, from a crafted post.

Sizes, read-only and disabled

Use Size to line up with buttons and other fields, ReadOnly for text that posts but can't change, and Disabled for text that doesn't post.

Preview Code

Preview

Code

States.razor

<Form Model="Model" FormName="text-area-states" MaxWidth="28.Rem" Grow>
    <TextArea @bind-Value="Model!.Small" Label="Small" Size="ControlSize.Sm" Rows="2" />
    <TextArea @bind-Value="Model!.Large" Label="Large" Size="ControlSize.Lg" Rows="2" />
    <TextArea @bind-Value="Model!.Terms" Label="Terms" Rows="2" ReadOnly Hint="Read-only: posted, but can't be changed." />
    <TextArea @bind-Value="Model!.Notes" Label="Internal notes" Rows="2" Disabled Hint="Disabled: not posted." />
</Form>

@code {
    [SupplyParameterFromForm(FormName = "text-area-states")]
    private Contract? Model { get; set; }

    protected override void OnInitialized() => Model ??= new();

    public sealed class Contract
    {
        public string? Small { get; set; } = "Net 30.";
        public string? Large { get; set; } = "Renews every year.";
        public string? Terms { get; set; } = "Payment is due 30 days after the invoice date.";
        public string? Notes { get; set; } = "Ask about a three-year term at renewal.";
    }
}

Read-only text can still be selected and copied, and it posts like any other, so a crafted post can change it: check it on the server if it matters. A disabled field posts nothing, so after a static post its property is null: keep its value on the server rather than saving it from the post.

Mode support

What works in each mode, TextArea
Feature	Off	Static	Live
Label, hint and length limits from the model	Yes	Yes	Yes
Checks before posting, server messages under the field	Yes	Yes	Yes
Grows with the text (AutoGrow)	Yes	Yes	Yes
The count follows typing (ShowCount)	No	Yes	Yes

Off: JavaScript disabled. Static: a static SSR page with IzzyBlazor's script. Live: an interactive page (Server, WebAssembly or Auto).

Accessibility

Label, hint and errors work as in TextField: a linked label, aria-describedby and aria-invalid.
With a maximum length, the browser stops typing at the limit (maxlength).
With script, the ShowCount counter ("12 / 200") is the field's description, after the hint and errors, so screen readers read it on focus; it isn't announced as it changes. With JavaScript off it doesn't update, so it isn't linked.

Parameters

TextArea parameters
Prop	Type	Default
`ReadOnly`Makes the field read-only: it can be focused and its text selected, and it still posts.	`bool`	`false`
`Rows`Visible lines.	`int`	`4`
`AutoGrow`Grows with the text instead of scrolling, from Rows lines up, where the browser supports CSS field-sizing.	`bool`	`false`
`Placeholder`Example text shown when empty.	`string?`
`MaxLength`Maximum length.	`int?`	`computed`
`MinLength`Minimum length.	`int?`	`computed`
`ShowCount`Shows "n / max" under the field.	`bool`	`false`
`@bind-Value`The value, bound with @bind-Value.	`string?`
`DisplayName`The field's name in validation messages from the input itself, such as a value that can't be parsed.	`string?`

Plus 26 field props.

Full API