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    Vue dotnet validator

    A vuejs validator for .NET forms.

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    This package makes it possible to use .NET model validation using vue.js instead of the default jQuery validator way that microsoft dictates. The idea is that you use this on your server rendered HTML forms which include the data-attributes that are generated by C#'s razor template engine.


    This package (from version 0.3.0 and up) requires vue 2.x.


    npm install vue-dotnet-validator


    Using this library requires changes on two places in your application, JavaScript and your razor cshtml templates.


    This registers the vue components so that Vue.js knows what to activate. Base usage:

    import { validatorGroup, validator } from 'vue-dotnet-validator';
    Vue.component('validator-group', validatorGroup);
    Vue.component('validator', validator());


    The following code should be added to your cshtml forms. This makes sure that the validator logic is activated and adds the required references to DOM-nodes.

    <validator-group inline-template>
        <form asp-controller="Account" asp-action="Register" method="post" v-on:submit="validate">
            <validator value="@Model.LastName" inline-template>
               <span asp-validation-for="LastName" ref="message"></span>
               <input type="text" asp-for="LastName" ref="field" v-model="val" />
            <button type="submit">Register</button>

    Explanation of the cshtml changes:

    <validator-group inline-template>

    This behaves as a container for the entire form, so we can maintain the state of the entire form and the validation status of the input fields in it.


    This adds an event listener to the <form> tag to make sure we prevent the default form submit event when fields are invalid.

    <validator value="@Model.LastName" inline-template>

    This adds a validator instance to the form. The @Model.LastName is the property of your model.


    This adds a reference to the validation-message element. This makes sure the validation message is displayed at the correct position in the DOM.


    This adds a reference to the input field, so the <validator> instance knows what element to watch.


    This adds the model binding in the <validator> instance.

    validation-style="" (optional, default is after-blur), validation-styles:

    • after-blur (default): After first blur validation will be reactive.
    • after-change: After first change validation will be reactive, blurring an autofocus field with no input will not trigger this.
    • after-submit: After first submit validation will be reactive.


    This prioritizes the (optional) extra error messages over the normal validation messages.

    Built-in validators

    There are a couple of built-in validators you can use.

    Required Validator

    To validate if a value is not null, undefined or empty-string.

    Is True Validator

    To validate a value (for example a checkbox) is set to true.

    Equal To Validator

    To validate a value is equal to the value of another input-field based on it's name attribute.

    Regex Validator

    To validate a value complies to a regex.

    Range Validator

    To validate a numeric value is in a range between.

    String-length Validator

    To validate a string value length is in a range between.

    Min-length Validator

    To validate a string value has a minimum length.

    Max-length Validator

    To validate a string is not longer than a maximum length.

    Creating custom validators

    It is possible to create your own validators, below is an example of a very simple custom validator.


    import { validator, BaseValidator } from 'vue-dotnet-validator';
    class MyCustomValidator extends BaseValidator {
        isValid(value) {
            return !value || value == 'Hello';
    const validators = {
    Vue.component('validator', validator(validators));


    To use this custom validator in your own form, make sure your custom .NET data annotation outputs a data-val-mycustom="MESSAGE" attribute on your <input> DOM node.

    Custom validators with additional parameters

    You can extend the features of your custom validators using additional data-attributes on your <input> tag. This is a feature supported in .NET. For an example on the usage of this feature, see regexvalidator.js.

    Publish a new version

    Make sure you have publish rights at the Q42 organisation on NPM.

    npm version [major|minor|patch]
    npm publish


    npm i vue-dotnet-validator

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