c# - mvc 4下拉选择默认值

Question

我想在 policyId = 7 的下拉列表中选择默认值，但它没有选择该值，我做错了什么？

Controller :

var pm = new ManagerClass();
IEnumerable<myClass> po = pm.GetDataFromDb();
IEnumerable<SelectListItem> Policies = new SelectList(po, "PolicyID", "PolicyName", new { PolicyID = 7 });
ViewBag.Policies = Policies;

查看:

@Html.DropDownListFor(m => m.PolicyID, ViewBag.Policies as IEnumerable<SelectListItem>, new { @class = "dropdown-field"})

Answer 1

这是因为它实际上并没有选择SelectList中的值。

首先，为了让它更好，将项目放在 View 模型中以防止转换(这也是更好的做法):

public class MyModel
{
    public int PolicyID { get; set; }
    public List<SelectListItem> Policies { get; set; }
    //rest of your model
}

然后填充它:

var model = new MyModel();
model.Policies = po
    .Select(p => new SelectListItem
    {
        Text = p.PolicyName,
        Value = p.PolicyID.ToString(),
        Selected = p.PolicyID == currentPolicyId //change that to whatever current is
    })
    .ToList();

然后在你看来，做:

@Html.DropDownListFor(m => m.PolicyID, Model.Policies, new { @class = "dropdown-field"})