包括使用ViewBag中的DropDownList绑定“全部”选项 [英] Include 'ALL' option in dropdownlist bind using ViewBag

问题描述

我有Viewbag从控制器绑定鉴于DropDownList中如下：

I have bind the dropdownlist in view by Viewbag from controller as following :

ViewBag.test = from p in _userRegisterViewModel.GetEmpPrimary().ToList().Where(a => a.UserType_id != Convert.ToInt32(Session["loginUserType"].ToString()))
                           select new
                           {
                Id = p.EmpId,
                Name =  p.First_Name.Trim() + " " + p.Last_Name.Trim()
            };

在视图我有绑定如下：

@Html.DropDownListFor(model => model.EmpId, new SelectList(@ViewBag.test, "Id", "Name"),
                        new { @class = "form-control", id="ddlEmp" })

现在我想在这个DropDownList中插入ALL和 - 选择 - ..我怎样才能做到这一点..
谁能帮我做到这一点..
在此先感谢..

Now i want to Insert "ALL" and "--Select--" in this dropdownlist.. How can i do this.. Can anyone help me to do this.. Thanks in advance..

推荐答案

您可以通过使用的<一个添加空选项将DropDownList href=\"https://msdn.microsoft.com/en-us/library/system.web.mvc.html.selectextensions.dropdownlistfor(v=vs.118).aspx#M:System.Web.Mvc.Html.SelectExtensions.DropDownListFor%3C$c$c%3E2%28System.Web.Mvc.HtmlHelper%7B%3C/$c$c%3E0%7D,System.Linq.Ex$p$pssions.Ex$p$pssion%7BSystem.Func%7B%3C$c$c%3E0,%3C/$c$c%3E1%7D%7D,System.Collections.Generic.IEnumerable%7BSystem.Web.Mvc.SelectListItem%7D,System.String%29\"相对=nofollow>重载 DropDownlistFor（），接受一个 optionLabel ，例如<的/ p>

You can add a null option to the dropdownlist by using one of the overloads of DropDownlistFor() that accepts a optionLabel, for example

@Html.DropDownListFor(m => m.EmpId, new SelectList(@ViewBag.test, "Id", "Name"), "--select--", new { @class = "form-control", id="ddlEmp" })

这将产生第一个选项为＆LT;期权价值=＆GT; - 选择 - ＆LT; /选项＆GT;

不过，如果你想包括两个选项 - 选择 - 和全部你需要生成你自己的的IEnumerable＆LT; SelectListItem＆GT; 控制器并把它传递给视图。我会建议使用带有的IEnumerable＆LT视图模型; SelectListItem＆GT; 属性的选项，但使用 ViewBag 中，$ C在控制器$ C将

However, if you want to include options with both "--select--" and "ALL" you will need to generate you own IEnumerable<SelectListItem> in the controller and pass it to the view. I would recommend using view model with a IEnumerable<SelectListItem> property for the options, but using ViewBag, the code in the controller would be

List<SelectListItem> options = _userRegisterViewModel.GetEmpPrimary()
    .Where(a => a.UserType_id != Convert.ToInt32(Session["loginUserType"].ToString()))
    .Select(a => new SelectListItem
    {
        Value = a.EmpId.ToString(),
        Text = a.First_Name.Trim() + " " + a.Last_Name.Trim()
    }).ToList();
// add the 'ALL' option
options.Add(new SelectListItem(){ Value = "-1", Text = "ALL" });
ViewBag.test = options;

请注意，我已经给出了所有选项 1 假设值，没有你的<$ C的$ C> EMPID 值将 1

Note that I have given the ALL option a value of -1 assuming that none of your EmpId values will be -1

然后在视图中，您的code产生的DropDownList将

Then in the view, your code to generate the dropdownlist will be

 @Html.DropDownListFor(m => m.EmpId, (Ienumerable<SelectListItem>)ViewBag.test, "--select--", new { @class = "form-control" })

不知道为什么你想修改 ID 从 ID =EMPID属性 ID =ddlEmp？

然后在POST方法，首先检查的ModelState 是无效的（如果用户选择了 - 选择 - 选项，值空将被张贴和模式将是无效的），所以返回视图（不要忘了重新分配 ViewBag.test 属性）。

Then in the POST method, first check if ModelState is invalid (if the user selected the "--select--" option, a value of null will be posted and the model will be invalid), so return the view (don't forget to reassign the ViewBag.test property).

如果的ModelState 是否有效，然后检查 model.EmpId 的价值。如果它的 1 ，然后选择用户全部，不然就选择了特定的选项。

If ModelState is valid, then check the value of model.EmpId. If its -1, then the user selected "ALL", otherwise they selected a specific option.

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