Blazor Number Input

Blazor Bootstrap NumberInput component is built around HTML input of type="number" that prevents the user input based on the parameters set.

Parameters

Name	Type	Default	Required	Description
AllowNegativeNumbers	bool	false		Allows negative numbers. By default, negative numbers are not allowed.
AutoComplete	bool	false		Indicates whether the NumberInput can complete the values automatically by the browser.
Disabled	bool	false		Gets or sets the disabled.
EnableMinMax	bool	false		Determines whether to restrict the user input to Min and Max range. If true, restricts the user input between the Min and Max range. Else accepts the user input.
Locale	string	en-US	✔️	Gets or sets the locale.
Max	TValue			Gets or sets the max. Max ignored if EnableMinMax="false".
Min	TValue			Gets or sets the min. Min ignored if EnableMinMax="false".
Placeholder	string?	null		Gets or sets the placeholder.
Step	double?	null		Gets or sets the step.
TextAlignment	Alignment	Alignment.None		Gets or sets the text alignment.
Value	TValue			Gets or sets the value.

Methods

Name	Description
Disable()	Disables number input.
Enable()	Enables number input.

Events

Name	Description
ValueChanged	This event fired on every user keystroke that changes the NumberInput value.

Examples

Basic usage

By default, e + - are blocked. For all integral numeric types, dot . is blocked.

<div class="mb-3">
    <label class="form-label">Amount</label>
    <NumberInput TValue="int" @bind-Value="@amount" Placeholder="Enter amount" />
</div>
<div class="mb-3">Entered Amount: @amount</div>

@code {
    private int amount;
}

See demo here

Generic type

NumberInput is a generic component. Always specify the exact type. In the below example TValue is set to int, int?, float, float?, double, double?, decimal, and decimal?.

<div class="mb-3">
    <label class="form-label">Enter int number</label>
    <NumberInput TValue="int" @bind-Value="@amount" />
    <div class="mt-1">Entered Number: @amount</div>
</div>

<div class="mb-3">
    <label class="form-label">Enter int? number</label>
    <NumberInput TValue="int?" @bind-Value="@amount2" />
    <div class="mt-1">Entered Number: @amount2</div>
</div>

<div class="mb-3">
    <label class="form-label">Enter float number</label>
    <NumberInput TValue="float" @bind-Value="@amount3" />
    <div class="mt-1">Entered Number: @amount3</div>
</div>

<div class="mb-3">
    <label class="form-label">Enter float? number</label>
    <NumberInput TValue="float?" @bind-Value="@amount4" />
    <div class="mt-1">Entered Number: @amount4</div>
</div>

<div class="mb-3">
    <label class="form-label">Enter double number</label>
    <NumberInput TValue="double" @bind-Value="@amount5" />
    <div class="mt-1">Entered Number: @amount5</div>
</div>

<div class="mb-3">
    <label class="form-label">Enter double? number</label>
    <NumberInput TValue="double?" @bind-Value="@amount6" />
    <div class="mt-1">Entered Number: @amount6</div>
</div>

<div class="mb-3">
    <label class="form-label">Enter decimal number</label>
    <NumberInput TValue="decimal" @bind-Value="@amount7" />
    <div class="mt-1">Entered Number: @amount7</div>
</div>

<div class="mb-3">
    <label class="form-label">Enter decimal? number</label>
    <NumberInput TValue="decimal?" @bind-Value="@amount8" />
    <div class="mt-1">Entered Number: @amount8</div>
</div>

@code {
    private int amount;
    private int? amount2;
    private float amount3;
    private float? amount4;
    private double amount5;
    private double? amount6;
    private decimal amount7;
    private decimal? amount8;
}

See demo here

Enable min and max

Set EnableMinMax="true" and set the Min and Max parameters to restrict the user input between the Min and Max range.

NOTE

If the user tries to enter a number in the NumberInput field which is out of range, then it will override with Min or Max value based on the context. If the user input is less than the Min value, then it will override with the Min value. If the user input exceeds the Max value, it will override with the Max value.

<div class="mb-3">
    <label class="form-label">Amount</label>
    <NumberInput TValue="decimal?" @bind-Value="@amount" EnableMinMax="true" Min="10" Max="500" Placeholder="Enter amount" />
    <span class="form-text">Tip: The amount must be between 10 and 500.</span>
</div>
<div class="mb-3">Entered Amount: @amount</div>

@code {
    private decimal? amount;
}

See demo here

Step

The Step sets the stepping interval when clicking the up and down spinner buttons. If not explicitly included, Step defaults to 1.

<div class="mb-3">
    <label class="form-label">Amount</label>
    <NumberInput TValue="int?" @bind-Value="@amount" Step="10" Placeholder="Enter amount" />
    <span class="form-text">Info: Here <code>Step</code> parameter is set to <b>10</b>.</span>
</div>
<div class="mb-3">Entered Amount: @amount</div>

<div class="mb-3">
    <label class="form-label">Amount</label>
    <NumberInput TValue="decimal?" @bind-Value="@amount2" Step="2.5" Placeholder="Enter amount" />
    <span class="form-text">Info: Here <code>Step</code> parameter is set to <b>2.5</b>.</span>
</div>
<div class="mb-3">Entered Amount: @amount2</div>

@code {
    private int? amount;
    private decimal? amount2;
}

See demo here

Text alignment

You can change the text alignment according to your need. Use the TextAlignment parameter to set the alignment. In the below example, alignment is set to center and end.

<div class="mb-3">
    <label class="form-label">Amount</label>
    <NumberInput TValue="int" @bind-Value="@amount" TextAlignment="Alignment.Center" Placeholder="Enter amount" />
</div>
<div class="mb-3">Entered Amount: @amount</div>

<div class="mb-3">
    <label class="form-label">Amount</label>
    <NumberInput TValue="decimal" @bind-Value="@amount2" TextAlignment="Alignment.End" Placeholder="Enter amount" />
</div>
<div class="mb-3">Entered Amount: @amount2</div>

@code {
    private int amount;
    private decimal amount2 = 2.34M;
}

See demo here

Allow negative numbers

By default, negative numbers are not allowed. Set the AllowNegativeNumbers parameter to true to allow the negative numbers.

<div class="mb-3">
    <label class="form-label">Amount</label>
    <NumberInput TValue="int" @bind-Value="@amount" AllowNegativeNumbers="true" Placeholder="Enter amount" />
    <span class="form-text">Tip: Negative numbers are also allowed.</span>
</div>
<div class="mb-3">Entered Amount: @amount</div>

@code {
    private int amount;
}

See demo here

Disable

Use the Disabled parameter to disable the NumberInput.

<div class="mb-3">
    <label class="form-label">Amount</label>
    <NumberInput TValue="int?"
                 @bind-Value="@amount"
                 Disabled="@disabled"
                 Placeholder="Enter amount" />
</div>

<Button Color="ButtonColor.Primary" @onclick="Enable"> Enable </Button>
<Button Color="ButtonColor.Secondary" @onclick="Disable"> Disable </Button>
<Button Color="ButtonColor.Warning" @onclick="Toggle"> Toggle </Button>

@code {
    private int? amount;
    private bool disabled = true;

    private void Enable() => disabled = false;

    private void Disable() => disabled = true;

    private void Toggle() => disabled = !disabled;
}

Also, use Enable() and Disable() methods to enable and disable the NumberInput.

NOTE

Do not use both the Disabled parameter and Enable() & Disable() methods.

<div class="mb-3">
    <label class="form-label">Amount</label>
    <NumberInput @ref="numberInput" 
                 TValue="int?" 
                 @bind-Value="@amount" 
                 Placeholder="Enter amount" />
</div>

<Button Color="ButtonColor.Secondary" @onclick="Disable"> Disable </Button>
<Button Color="ButtonColor.Primary" @onclick="Enable"> Enable </Button>

@code {
    private NumberInput<int?> numberInput = default!;
    private int? amount;

    private void Disable() => numberInput.Disable();

    private void Enable() => numberInput.Enable();
}

See demo here

Validations

Like any other blazor input component, NumberInput supports validations. Add the DataAnnotations on the NumberInput component to validate the user input before submitting the form. In the below example, we used Required and Range attributes.

@using System.ComponentModel.DataAnnotations

<style>
    .valid.modified:not([type=checkbox]) {
        outline: 1px solid #26b050;
    }

    .invalid {
        outline: 1px solid red;
    }

    .validation-message {
        color: red;
    }
</style>

<EditForm EditContext="@editContext" OnValidSubmit="HandleOnValidSubmit">
    <DataAnnotationsValidator />

    <div class="form-group row mb-3">
        <label class="col-md-2 col-form-label">Item Price: <span class="text-danger">*</span></label>
        <div class="col-md-10">
            <NumberInput TValue="decimal?" Value="invoice.Price" ValueExpression="() => invoice.Price" ValueChanged="(value) => PriceChanged(value)" Placeholder="Enter price" />
            <ValidationMessage For="@(() => invoice.Price)" />
        </div>
    </div>

    <div class="form-group row mb-3">
        <label class="col-md-2 col-form-label">Item Discount:</label>
        <div class="col-md-10">
            <NumberInput TValue="decimal?" Value="invoice.Discount" ValueExpression="() => invoice.Discount" ValueChanged="(value) => DiscountChanged(value)" Placeholder="Enter discount" />
            <ValidationMessage For="@(() => invoice.Discount)" />
        </div>
    </div>

    <div class="form-group row mb-3">
        <label class="col-md-2 col-form-label">Total Amount: <span class="text-danger">*</span></label>
        <div class="col-md-10">
            <NumberInput TValue="decimal?" @bind-Value="invoice.Total" Disabled="true" Placeholder="Enter total" />
            <ValidationMessage For="@(() => invoice.Total)" />
        </div>
    </div>

    <div class="row">
        <div class="col-md-12 text-right">
            <Button Type="ButtonType.Button" Color="ButtonColor.Secondary" Class="float-end" @onclick="ResetForm">Reset</Button>
            <Button Type="ButtonType.Submit" Color="ButtonColor.Success" Class="float-end me-2">Submit</Button>
        </div>
    </div>
</EditForm>

@code {
    private Invoice invoice = new();
    private EditContext editContext;

    protected override void OnInitialized()
    {
        editContext = new EditContext(invoice);
        base.OnInitialized();
    }

    protected override void OnParametersSet()
    {
        CalculateToatl();
        base.OnParametersSet();
    }

    private void PriceChanged(decimal? value)
    {
        invoice.Price = value;
        CalculateToatl();
    }

    private void DiscountChanged(decimal? value)
    {
        invoice.Discount = value;
        CalculateToatl();
    }

    private void CalculateToatl()
    {
        var price = invoice.Price.HasValue ? invoice.Price.Value : 0;
        var discount = invoice.Discount.HasValue ? invoice.Discount.Value : 0;
        invoice.Total = price - discount;
    }

    public void HandleOnValidSubmit()
    {
        Console.WriteLine($"Price: {invoice.Price}");
        Console.WriteLine($"Discount: {invoice.Discount}");
        Console.WriteLine($"Total: {invoice.Total}");
    }

    private void ResetForm()
    {
        invoice = new();
        editContext = new EditContext(invoice);
    }

    public class Invoice
    {
        [Required(ErrorMessage = "Price required.")]
        [Range(60, 500, ErrorMessage = "Price should be between 60 and 500.")]
        public decimal? Price { get; set; } = 232M;

        [Range(0, 50, ErrorMessage = "Discount should be between 0 and 50.")]
        public decimal? Discount { get; set; }

        [Required(ErrorMessage = "Amount required.")]
        [Range(10, 500, ErrorMessage = "Total should be between 60 and 500.")]
        public decimal? Total { get; set; }
    }
}

See demo here

Events: ValueChanged

This event fires on every user keystroke that changes the NumberInput value.

<div class="row mb-3">
    <label class="col-md-2 col-form-label">Item Price: <span class="text-danger">*</span></label>
    <div class="col-md-10">
        <NumberInput TValue="decimal?" Value="price" ValueExpression="() => price" ValueChanged="(value) => PriceChanged(value)" Placeholder="Enter price" />
    </div>
</div>
<div>
    @displayPrice
</div>

@code {
    private decimal? price = 10M;
    private string displayPrice;

    private void PriceChanged(decimal? value)
    {
        price = value; // this is mandatory
        displayPrice = $"Price: {value}, changed at {DateTime.Now.ToLocalTime()}.";
    }
}

See demo here