作为第一个参数，您应该传递一个字段，用于在表单提交后接收数据.其他一切看起来都不错:

As a first parameter you should pass a field for what you are going to receive data after form submit. Everything else looks right:

@Html.DropDownListFor(model=>model.UserId, Model.Users)

或者，如果您要提供自己的 ID 和名称 - ***使用它 (msdn):

Or if you are going to provide your own id and name - it would be better to use this (msdn):

@Html.DropDownList("add-user-list", Model.Users, new {id = "add-user-list"})