asp.net mvc 下拉列表

using System;
using System.Collections;
using System.Collections.Generic;
using System.Data;
using System.Linq;
using System.Reflection;
using System.Text;
using System.Threading.Tasks;
using System.Web.Mvc;

namespace GmkGM.Infrastructure
{
    public class Common
    {
        /// <summary>
        /// 获取下拉列表（有层级结构）
        /// </summary>
        /// <param name="Id"></param>
        /// <returns></returns>
        public static IList<SelectListItem> GetDropdownList(IList listInfo,int? Id,string name)
        {
            DataTable ds = Common.ToDataSet(listInfo).Tables[0];

            if (null != ds && ds.Rows.Count > 0)
            {
                //添加一列
                ds.Columns.Add("Level", typeof(int));
                // 克隆dt 的结构，包括所有 dt 架构和约束,并无数据
                DataTable newDT = ds.Clone();
                DataTable catelist = Common.GetTreeList(ds, newDT, 0, 0);
                if (catelist.Rows.Count > 0)
                {
                    IList<SelectListItem> list = new List<SelectListItem>();
                    foreach (DataRow row in catelist.Rows)
                    {
                        SelectListItem item = new SelectListItem();
                        item.Value = Convert.ToString(row["ID"]);
                        string pri = "----";
                        var rt = row["Level"];
                        item.Text = row[name] == DBNull.Value ? string.Empty : Common.StringRepeat(pri, Convert.ToInt32(row["Level"]) + 1) + Convert.ToString(row[name]);

                        if (Id == Convert.ToInt32(item.Value))
                        {
                            item.Selected = true;
                        }

                        list.Add(item);
                    }
                    SelectListItem first = new SelectListItem();
                    first.Text = "--父类--";
                    first.Value = "0";
                    list.Insert(0, first);
                    return list;
                }
            }
            return null;
        }
        //无层级结构
        public static IList<SelectListItem> GetDropdownList2(IList listInfo, int? Id, string name)
        {
            if (listInfo.Count > 0)
            {
                DataTable ds = Common.ToDataSet(listInfo).Tables[0];

                if (null != ds && ds.Rows.Count > 0)
                {
                    IList<SelectListItem> list = new List<SelectListItem>();
                    foreach (DataRow row in ds.Rows)
                    {
                        SelectListItem item = new SelectListItem();
                        item.Value = Convert.ToString(row["ID"]);
                        item.Text = row[name] == DBNull.Value ? string.Empty : Convert.ToString(row[name]);

                        if (Id == Convert.ToInt32(item.Value))
                        {
                            item.Selected = true;
                        }

                        list.Add(item);
                    }
                    SelectListItem first = new SelectListItem();
                    first.Text = "--父类--";
                    first.Value = "0";
                    list.Insert(0, first);
                    return list;
                }
                return null;
            }
            return null;
        }
        /// <summary>
        /// 生成树形结构
        /// </summary>
        /// <param name="dt">数据源表</param>
        /// <param name="newDT">返回的结果表</param>
        /// <param name="Pid">父类ID值</param>
        /// <param name="level">层级</param>
        /// <returns></returns>
        public static DataTable GetTreeList(DataTable dt, DataTable newDT, int Pid, int level = 0)
        {
            for (int i = 0; i < dt.Rows.Count; i++)
            {
                if (Convert.ToInt32(dt.Rows[i]["Pid"]) == Pid)
                {
                    //用来标记这个分类是第几级的
                    dt.Rows[i]["Level"] = level;
                    newDT.Rows.Add(dt.Rows[i].ItemArray);
                    //找子分类
                    DataTable innerDT = GetTreeList(dt, newDT, Convert.ToInt32(dt.Rows[i]["Id"]), level + 1);
                }
            }
            return newDT;
        }

        /// <param name="str">字符串</param>
        /// <param name="n">重复次数</param>
        public static string StringRepeat(string str, int n)
        {
            if (String.IsNullOrEmpty(str) || n <= 0)
                return str;
            StringBuilder sb = new StringBuilder();
            while (n > 0)
            {
                sb.Append(str);
                n--;
            }
            return sb.ToString();
        }
        // list转换为DataSet   
        public static DataSet ToDataSet(IList p_List)
        {
            DataSet result = new DataSet();
            DataTable _DataTable = new DataTable();
            if (p_List.Count > 0)
            {
                PropertyInfo[] propertys = p_List[0].GetType().GetProperties();
                foreach (PropertyInfo pi in propertys)
                {
                    _DataTable.Columns.Add(pi.Name, pi.PropertyType);
                }

                for (int i = 0; i < p_List.Count; i++)
                {
                    ArrayList tempList = new ArrayList();
                    foreach (PropertyInfo pi in propertys)
                    {
                        object obj = pi.GetValue(p_List[i], null);
                        tempList.Add(obj);
                    }
                    object[] array = tempList.ToArray();
                    _DataTable.LoadDataRow(array, true);
                }
            }
            result.Tables.Add(_DataTable);
            return result;
        }
        /// <summary>
        /// 找出一个分类所有子分类的ID
        /// </summary>
        /// <param name="catId"></param>
        /// 
        /// <returns></returns>
        public static DataTable GetChildren(DataTable dt, int catId)
        {
            //定义一个表存放保存找到的子分类的id
            DataTable newDT = new DataTable();
            //添加一列
            newDT.Columns.Add("CID", typeof(int));
            if (dt != null && dt.Rows.Count > 0)
            {
                //循环所有的分类找子类
                for (int i = 0; i < dt.Rows.Count; i++)
                {
                    if (Convert.ToInt32(dt.Rows[i]["PID"]) == catId)
                    {
                        newDT.Rows.Add((Object)dt.Rows[i]["Id"]);
                        //再找这个$v的子分类
                        GetChildren(dt, Convert.ToInt32(dt.Rows[i]["Id"]));
                    }
                }
            }
            return newDT;
        }
    }
}

        public IList List2()
        {
            return db.Whse_Stock_List().ToList();
        }

        public IList<SelectListItem> GetProductDropdownList(int? Id)
        {
            return Common.GetDropdownList2(List2(), Id, "ProductName");
        }

        public IList List()
        {
            return db.Whse_Location_List().ToList();
        }

        public IList<SelectListItem> GetLocationDropdownList(int? Id)
        {
            return Common.GetDropdownList(List(), Id,"Code");
        }

        // GET: Inventory/Create
        public ActionResult Create()
        {
            #region 产品下拉列表
            ViewBag.ProductTypes = new InventoryService().GetProductDropdownList(null);
            #endregion

            #region 仓库位置下拉列表
            ViewBag.LocationTypes = new InventoryService().GetLocationDropdownList(null);
            #endregion

            return View();
        }
        [ValidateAntiForgeryToken]
        [HttpPost]
        public ActionResult Create(Inventory model)
        {
            try
            {
                #region 产品下拉列表
                ViewBag.ProductTypes = new InventoryService().GetProductDropdownList(model.StockID);
                #endregion

                #region 仓库位置下拉列表
                ViewBag.LocationTypes = new InventoryService().GetLocationDropdownList(model.LocationID);
                #endregion

                //验证模型是否有效
                if (ModelState.IsValid)
                {
                    bool res = new InventoryService().Insert(model);
                    if (!res)
                    {
                        TempData[LastMessageInfoKey.LastErrorMessageTempDataKey] = "创建失败!";
                        return View(model);
                    }
                    TempData[LastMessageInfoKey.LastSuccessMessageTempDataKey] = "创建成功!";
                    return RedirectToAction("Index");
                }
                else
                {
                    return View(model);
                }
            }
            catch (Exception ex)
            {
                TempData[LastMessageInfoKey.LastErrorMessageTempDataKey] = ex.Message;
                return View(model);
            }
        }
        // GET: Inventory/Edit/5
        public ActionResult Edit(int StockID, int LocationID)
        {
            InventoryModel Inventory = service.Get(StockID,LocationID);

            #region 产品下拉列表
            ViewBag.ProductTypes = new InventoryService().GetProductDropdownList(StockID);
            #endregion

            #region 仓库位置下拉列表
            ViewBag.LocationTypes = new InventoryService().GetLocationDropdownList(LocationID);
            #endregion

            return View(Inventory);
        }

        [ValidateAntiForgeryToken]
        [HttpPost]
        public ActionResult Edit(Inventory model)
        {
            try
            {
                #region 产品下拉列表
                ViewBag.ProductTypes = new InventoryService().GetProductDropdownList(model.StockID);
                #endregion

                #region 仓库位置下拉列表
                ViewBag.LocationTypes = new InventoryService().GetLocationDropdownList(model.LocationID);
                #endregion

                //验证模型是否有效
                if (ModelState.IsValid)
                {
                    bool res = service.Update(model);
                    if (!res)
                    {
                        TempData[LastMessageInfoKey.LastErrorMessageTempDataKey] = "编辑失败!";
                        return View(model);
                    }
                    TempData[LastMessageInfoKey.LastSuccessMessageTempDataKey] = "编辑成功!";
                    return RedirectToAction("Index");
                }
                else
                {
                    return View(model);
                }
            }
            catch (Exception ex)
            {
                TempData[LastMessageInfoKey.LastErrorMessageTempDataKey] = ex.Message;
                return View(model);
            }
        }

@model GmkGM.Whse.Model.Inventory
@{
    ViewBag.Title = "Create";
}

@section styles{
    @Styles.Render("~/bundles/form/css")
}

@section scripts{
    @Scripts.Render("~/bundles/form/js")
}

@using (Html.BeginForm(null, null, FormMethod.Post, new { @class = "form-horizontal", role = "form" }))
{
    @Html.AntiForgeryToken()

    <div class="row">
        <div class="col-xs-12">
            <fieldset>
                @Html.LabelFor(model => model.StockID)（必填）
                @if (ViewBag.ProductTypes != null)
                {
                    @Html.DropDownList("StockID", ViewBag.ProductTypes as IEnumerable<SelectListItem>, new { @class = "form-control" })
                }
                else
                {
                    <select id="StockID" name="StockID" class="form-control"></select>
                }
            </fieldset>
            <fieldset>
                @Html.LabelFor(model => model.LocationID)（必填）
                @if (ViewBag.LocationTypes != null)
                {
                    @Html.DropDownList("LocationID", ViewBag.LocationTypes as IEnumerable<SelectListItem>, new { @class = "form-control" })
                }
                else
                {
                    <select id="LocationID" name="LocationID" class="form-control"></select>
                }
            </fieldset>

            <fieldset>
                @Html.LabelFor(model => model.Balance)（必填）
                @Html.EditorFor(model => model.Balance, new { htmlAttributes = new { @class = "form-control" } })
                @Html.ValidationMessageFor(model => model.Balance, "", new { @Style = "color:red" })
            </fieldset>
        </div>
    </div>
    <div class="form-actions center">
        <button class="btn btn-sm btn-success" type="submit">
            提交
            <i class="ace-icon fa fa-arrow-right icon-on-right bigger-110"></i>
        </button>

        <a class="btn btn-sm btn-warning" href="@Url.Action("Index")">
            返回
            <i class="ace-icon fa fa-undo bigger-110"></i>
        </a>
    </div>
}