c# - 在 asp.net mvc 中，下拉列表值始终返回零

Question

这是模型类的示例

[Required(ErrorMessage = "Department is required")]
[Display(Name = "Department")]
public int SelectedValue { get; set; }


[Required(ErrorMessage = "Department is required")]
[Display(Name = "Department")]
public List<Department> RoleList { get; set; }

这是 View

<div class="col-md-10">
    @Html.DropDownListFor(m => m.RoleList, new SelectList(Model.RoleList,"ID", "RoleName","1"), "Please Choose a Department", new { htmlAttributes = new { @class = "form-control"} })
    @Html.ValidationMessageFor(model => model.SelectedValue, "",new { @class = "text-danger"})
</div>

该列表完全来自数据库。现在当我选择列表中的项目时，选择值必须发送到 Controller

public async Task<ActionResult> Register(RegisterViewModel model)
{
    int Selectedvalue = model.SelectedValue;
    if (ModelState.IsValid && (model.SelectedValue).ToString() != "0")
    {

这里我做了一个选择

错误

Answer 1

你应该改变它

@Html.DropDownListFor(m => m.RoleList, new SelectList(Model.RoleList,"ID", "RoleName","1"), "Please Choose a Department", new { htmlAttributes = new { @class = "form-control"} })

到

@Html.DropDownListFor(m => m.SelectedValue, new SelectList(Model.RoleList,"ID", "RoleName","1"), "Please Choose a Department", new { htmlAttributes = new { @class = "form-control"} })

DropDownListFor 的第一个参数应该是模型中的选定值。在您的情况下，此属性是 Model.SelectedValue 而不是 Model.RoleList。