ASP.NET MVC中如何将CaTrúc下拉列表加入Linq多条件搜索？

步骤1：修改控制器Action参数 #

在Index方法的参数列表中添加CaTrúc对应的筛选参数，参数类型根据数据库中CaTrúc字段的实际类型调整（示例用字符串类型）：

public ActionResult Index(DateTime? start, DateTime? end, string caTruc)

步骤2：集成Linq的Where筛选逻辑 #

在原有日期筛选的基础上，添加CaTrúc的条件判断，需处理用户未选择下拉选项的情况（此时不应用该筛选）：

var result = db.View_XeQuaTramReport
    .Where(r => r.NgayCa >= strStart && r.NgayCa <= strEnd)
    // 新增CaTrúc筛选：如果筛选值为空则跳过，否则匹配对应值
    .Where(r => string.IsNullOrEmpty(caTruc) || r.CaTruc == caTruc)
    .GroupBy(r => new { r.LoaiVe, r.LoaiXe, r.Phi })
    .Select(g => new XeQuaTramDTO
    {
        LoaiVe = g.Key.LoaiVe,
        LoaiXe = g.Key.LoaiXe,
        Phi = g.Key.Phi,
        TongPhi = g.Sum(r => r.Phi),
        TongXe = g.Count()
    })
    .OrderBy(r => new { r.LoaiVe, r.LoaiXe, r.Phi, r.TongPhi, r.TongXe })
    .ToList();

如果数据库中CaTrúc是数值类型（比如int），则调整参数和判断逻辑：

// 参数改为可空整数类型
public ActionResult Index(DateTime? start, DateTime? end, int? caTruc)

// 筛选逻辑改为
.Where(r => !caTruc.HasValue || r.CaTruc == caTruc.Value)

步骤3：在视图中添加下拉筛选控件 #

在报表搜索表单里添加CaTrúc下拉列表，可从数据库动态获取选项或硬编码：

动态获取选项（从数据库表读取）

<div class="form-group">
    @Html.Label("CaTrúc", htmlAttributes: new { @class = "control-label col-md-2" })
    <div class="col-md-10">
        @Html.DropDownList("caTruc", new SelectList(db.CaTrucList.Select(c => new { Value = c.MaCa, Text = c.TenCa }), "Value", "Text"), "全部", new { @class = "form-control" })
    </div>
</div>

硬编码选项

<div class="form-group">
    @Html.Label("CaTrúc", htmlAttributes: new { @class = "control-label col-md-2" })
    <div class="col-md-10">
        @Html.DropDownList("caTruc", new List<SelectListItem>
        {
            new SelectListItem { Text = "Ca 1", Value = "1" },
            new SelectListItem { Text = "Ca 2", Value = "2" },
            new SelectListItem { Text = "Ca 3", Value = "3" }
        }, "全部", new { @class = "form-control" })
    </div>
</div>

完整修改后的控制器代码 #

public DongphuocDbContext db = new DongphuocDbContext();

// GET: Report
public ActionResult Index(DateTime? start, DateTime? end, string caTruc)
{
    if (start == null || end == null)
    {
        return View();
    }
    DateTime strStart = start.Value.Date;
    DateTime strEnd = end.Value.Date;
    var result = db.View_XeQuaTramReport
        .Where(r => r.NgayCa >= strStart && r.NgayCa <= strEnd)
        .Where(r => string.IsNullOrEmpty(caTruc) || r.CaTruc == caTruc)
        .GroupBy(r => new { r.LoaiVe, r.LoaiXe, r.Phi })
        .Select(g => new XeQuaTramDTO
        {
            LoaiVe = g.Key.LoaiVe,
            LoaiXe = g.Key.LoaiXe,
            Phi = g.Key.Phi,
            TongPhi = g.Sum(r => r.Phi),
            TongXe = g.Count()
        })
        .OrderBy(r => new { r.LoaiVe, r.LoaiXe, r.Phi, r.TongPhi, r.TongXe })
        .ToList();

    return View(result);
}

内容的提问来源于stack exchange，提问作者Phatt