ASP.NET Core - Custom model validation : <p>In MVC when we post a model to an action we do the following in order to validate the model against the data annotation of that model:</p>

<pre><code>if (ModelState.IsValid)
</code></pre>

<p>If we mark a property as [Required], the ModelState.IsValid will validate that property if contains a value or not.</p>

<p>My question: How can I manually build and run custom validator?</p>

<p>P.S. I am talking about backend validator only.</p>
