Blazor Signature Overview

This article provides information about the Blazor Signature component and its core features.

The Blazor Signature component provides an area where users can draw their signatures with a mouse, pen, or with their fingertips. You can use the component in any application where the users must sign a document. The Blazor Signature integrates easily with the TelerikForm. The component stores the value of the signature as a base64 string

Telerik UI for Blazor Ninja image

The Signature component is part of Telerik UI for Blazor, a professional grade UI library with 100 native components for building modern and feature-rich applications. To try it out sign up for a free 30-day trial.

Creating Blazor Signature

  1. Use the TelerikSignature tag to add the component to your razor page.
  2. Set the Value parameter to a string property. It supports one-way and two-way binding.
  3. Set the Width and Height parameters to px values.
  4. Increase the SignalR Message Size

Blazor Signature with basic configuration

<TelerikSignature @bind-Value="@SignatureValue" Width="300px" Height="300px">
</TelerikSignature>

@code {
    private string SignatureValue { get; set; }
}

Appearance

The Signature component provides settings to control its appearance, for example colors and borders. Read more about the Blazor Signature appearance settings...

Events

Use the Blazor Signature blur and value change events to respond to user actions. Read more about the Blazor Signature events...

SignalR Message Size

In Blazor server-side applications, the Signature uses the SignalR WebSocket, which has a default maximum message size of 32 KB. To work with larger content, increase the max WebSocket message size for the Blazor application:

Program.cs (.NET 6)

using Microsoft.AspNetCore.SignalR;

var builder = WebApplication.CreateBuilder(args);

//...

// SignalR message size for the Signature
builder.Services.Configure<HubOptions>(options =>
{
    options.MaximumReceiveMessageSize = 1024 * 1024; // 1MB
});

Startup.cs (.NET 5)

public void ConfigureServices(IServiceCollection services)
{
    //...

    // SignalR message size for the Signature
    services.Configure<HubOptions>(options =>
    {
        options.MaximumReceiveMessageSize = 1024 * 1024; // 1MB
    });
}

Signature Parameters

The following table lists the Signature parameters. Also check the Signature API Reference.

Parameter Type and Default Value Description
AriaDescribedBy string Maps to the area-describedby attribute. Use this parameter to establish a relationship between widgets or groups and the text that describes them.
AriaLabel string Maps to the aria-label attribute. Use this parameter if the text that labels the component is not visible.
AriaLabelledBy string Maps to the area-labelledby attribute. Use this parameter to reference another element to define its accessible name.
Class string Renders a custom CSS class to the <div class="k-signature"> element. Use it to override theme styles.
DebounceDelay int
(150)
Time in milliseconds between the last typed symbol and the internal oninput event firing.
Enabled bool
(true)
Defines if the component is enabled.
ExportScale double
(2)
The Width and Height of the component will be multiplied by the value of the ExportScale when converting the signature to an image.
Height string Defines the height of the component. Set it in px.
HideLine bool Whether the dotted line is rendered.
Maximizable bool Whether the Signature component can be maximized.
PopupScale double The Width and Height of the component will be multiplied by the value of the PopupScale when maximizing (Maximizable="true") the Blazor Signature.
ReadOnly bool Maps to the readonly attribute. Use this parameter to put the Signature in read-only state.
Smooth bool Use this parameter to smoothen the signature line.
StrokeWidth double? The drawn lines' thickness in pixels.
TabIndex int? Maps to the tabindex attribute of the HTML element. You can use it to customize the order in which the inputs in your form focus with the Tab key.
ValidateOn ValidationEvent enum
(Input)
Configures the event that will trigger validation (if validation is enabled). Read more at Validation Modes for Simple Inputs.
Width string Defines the width of the component. Set the it in px.

Signature Reference and Methods

The Signature exposes methods for programmatic operation. To use them, define a reference to the component instance with the @ref directive attribute. The methods are:

Method Description
Refresh Use the method to programmatically re-render the Signature.

Obtain reference to the Signature instance and execute methods

@* Get a reference to the Signature component and refresh it on button click *@

<TelerikButton OnClick="@RefreshClickHandler">Refresh the Signature</TelerikButton>

<TelerikSignature @bind-Value="@SignatureValue"
                  Width="300px"
                  Height="300px"
                  @ref="@SignatureReference">
</TelerikSignature>

@code {
    private TelerikSignature SignatureReference { get; set; }

    private string SignatureValue { get; set; }

    private void RefreshClickHandler()
    {
        SignatureReference.Refresh();
    }
}

Next Steps

See Also

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