InputBlock.cs

public static HtmlTag InputBlock<T>(this HtmlHelper<T> helper,
    Expression<Func<T, object>> expression,
    Action<HtmlTag> inputModifier = null,
    Action<HtmlTag> validatorModifier = null) where T : class
{
    inputModifier = inputModifier ?? (_ => { });
    validatorModifier = validatorModifier ?? (_ => { });

    var divTag = new HtmlTag("div");
    divTag.AddClass("col-md-10");

    var inputTag = helper.Input(expression);
    inputModifier(inputTag);

    var validatorTag = helper.Validator(expression);
    validatorModifier(validatorTag);

    divTag.Append(inputTag);
    divTag.Append(validatorTag);

    return divTag;
}