Errors Model State Call Ajax

My suggestion: Since you are posting using Ajax and have Model with properties and validations, you can continue doing server-side validation, but only reloading the form.

First step: Transform your form into a PartialView

I'll call it "_MyPartialView". Example:

//Não colocar funções javascript aqui, elas não funcionam em PartialViews, mova-as para a tela principal.
@model MeuModel;
<form>
    @Html.TextboxFor(x=>x.Codigo)
</form>

And on your main screen, render PartialView:

<div id="divPrincipal">
     @Html.Partial("_MinhaPartialView", Model)
</div>

Second step: Make your Controller return to PartialView in case of validation failure

[HttpPost]
public ActionResult Save(MeuModel model) {
    if(ModelState.IsValid) {
        return Json(new {success = true});
    }

    return PartialView("_MinhaPartialView", model);
}

Thus, on success, the form will return a json containing the indication that it was successful. In case of model validation failure, it will return a html containing the entire form, including the validation messages.

Third step: Rendering the return of your Ajax function

$.ajax({
        url: '/Teste/Save',
        data: JSON.stringify(salesmain),
        type: 'POST',
        contentType: 'application/json;',
        //dataType: 'json', <-- REMOVER ESTA LINHA, AGORA A FUNÇÃO RETORNA JSON E HTML
        autoUpload: true,
        success: function (result) {
            if (result.success) {
                location.reload();
            }
            else 
            {
                document.getElementById('#divPrincipal').innerHTML = result;
                //Alternativa caso você use jQuery: $("#divPrincipal").html(result);
            }
        }
    });

In this way divPrincipal will replace your current form, without validation, with a new form containing the validations and error messages without reloading the page. And if you return a JSon indicating success, it will reload the entire page.

I found an article that explains how to do it. I tested it and it worked, follow the link:   link