For all the Devex Components, you can use ControlStyle > CssClass property to apply your custom CSS class (Example 1 and 2) or you can do it with parameter (if it is allowed – as in Example 3).
Here is 3 examples for MVC:
@Html.DevExpress().SpinEditFor(m => m.Books.Rating, settings =>
{
settings.Properties.SpinButtons.ShowIncrementButtons = true;
settings.Properties.Increment = 1m;
settings.Properties.NumberType = SpinEditNumberType.Integer;
settings.Properties.MinValue = 0m;
settings.Properties.MaxValue = 5m;
settings.ControlStyle.CssClass = "form-control";
}).GetHtml()
@Html.DevExpress().DateEdit(settings =>
{
settings.Name = "StartTime";
settings.ControlStyle.CssClass = "form-control";
}).GetHtml()
@Html.DropDownListFor(m => m.Books.AuthorId, new SelectList(Model.Authors, "Id", "AuthorFullName"), new { @class = "form-control" })
