linq中的值不同 [英] Distinct values in linq

问题描述

我尝试linq查询



< asp：DropDownList ID =regiondroprunat =serverAutoPostBack =True

onselectedindexchanged =regiondrop_SelectedIndexChanged>





我尝试在页面加载的下拉列表中显示不同的值。我尝试这个查询来获得



我尝试过：



价值



T1茶=新T1（）;

var list1 = tea.t1.ToList（）;

var list =（from list in list1

orderby ta.Region

select new {ta.Region，ta.RegionID}）。Distinct（）。ToList（） ;

但这显示了所有相同的值，因为我想要不同的值




我的方案数据中的
是



RID地区

1巴黎

2加拿大

3英国

4巴黎

5加拿大

伦敦

因此在加拿大和巴黎2次所以我希望这次1次在下拉菜单中



任何解决方案？

解决方案

尝试将它们分组：

列表< T1> list1 =  new 列表< T1>（）; 
 list1.Add（ new  T1 {RegionID =  1 ，Region =   Paris}）; 
 list1.Add（ new  T1 {RegionID =  2 ，Region =   Canada}）; 
 list1.Add（ new  T1 {RegionID =  3 ，Region =   UK}）; 
 list1.Add（ new  T1 {RegionID =  4 ，Region =   Paris}）; 
 list1.Add（ new  T1 {RegionID =  5 ，Region =   Canada}）; 
 list1.Add（ new  T1 {RegionID =  6 ，Region =   London}）; 
  var  list = 来自 ta   list1 
  group  ta by ta.Region  into  newgroup 
  orderby  newgroup.Key 
 选择 newgroup; 
  foreach （ var  t  in  list）
 {
 T1 t1 = t.First（）; 
 Console.WriteLine（  {0}：{1}，t1.RegionID， t1.Region）; 
} 
 

试试这个

  var  list1 = tea.t1.ToList（）; 
 Dictionary< int，string> dict =  new  Dictionary< int，string>（）; 
  foreach （ var  item  in  list1.OrderBy（k => k.Region））
 {
  if （！dict.ContainsValue（item.Region））
 dict.Add（item.RegionID，item.Region）; 
} 
  var  output = dict.Select（k = >   new  {RegionId = k.Key，Region = k.Value}）。ToList（）; 
 
 egiondrop.DataSource = output; 
 regiondrop.DataTextField =   Region; 
 regiondrop.DataValueField =   RegionId; 
 regiondrop.DataBind（）; 

Lambda解决方案：

 T1 tea =  new  T1（）; 
  var  list = tea.t1.GroupBy（x => x.Region）
。选择（grp => new 
 {
 RegionId = grp.First（），
 Region = grp.Key 
}）
 .ToList（）; 
  //  进一步 
 regiondrop.DataSource = list; 

I try linq query

<asp:DropDownList ID="regiondrop" runat="server" AutoPostBack="True"
onselectedindexchanged="regiondrop_SelectedIndexChanged">


I try to show distinct values in drop-down on page load. I try this query to get

What I have tried:

values

T1 tea = new T1();
var list1 = tea.t1.ToList();
var list = (from ta in list1
orderby ta.Region
select new { ta.Region,ta.RegionID }).Distinct().ToList();
but this shows all same values where as i want distinct values


in my scenario data is

RID Region
1 Paris
2 Canada
3 UK
4 Paris
5 Canada
6 London
so in this Canada and Paris 2 times so i want this 1 time in drop-down

any solution?

解决方案

Try Grouping them:

List<T1> list1 = new List<T1>();
list1.Add(new T1 { RegionID = 1, Region = "Paris" });
list1.Add(new T1 { RegionID = 2, Region = "Canada" });
list1.Add(new T1 { RegionID = 3, Region = "UK" });
list1.Add(new T1 { RegionID = 4, Region = "Paris" });
list1.Add(new T1 { RegionID = 5, Region = "Canada" });
list1.Add(new T1 { RegionID = 6, Region = "London" });
var list = from ta in list1
            group ta by ta.Region into newgroup
            orderby newgroup.Key
            select newgroup;
foreach (var t in list)
    {
    T1 t1 = t.First();
    Console.WriteLine("{0}:{1}", t1.RegionID, t1.Region);
    }

try this

var list1 = tea.t1.ToList();
     Dictionary<int, string> dict = new Dictionary<int, string>();
     foreach (var item in list1.OrderBy(k=>k.Region))
     {
         if(!dict.ContainsValue(item.Region))
         dict.Add(item.RegionID, item.Region);
     }
     var output = dict.Select(k => new { RegionId = k.Key, Region = k.Value }).ToList();

     egiondrop.DataSource = output;
     regiondrop.DataTextField = "Region";
     regiondrop.DataValueField = "RegionId";
     regiondrop.DataBind();

Lambda solution:

T1 tea = new T1();
var list = tea.t1.GroupBy(x=>x.Region)
                 .Select(grp=>new
                   {
                     RegionId = grp.First(),
                     Region = grp.Key
                   })
                 .ToList();
//further
regiondrop.DataSource = list;

这篇关于linq中的值不同的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！