Question

我无法以动态方式选择行。

foreach (var item in _listBox.SelectedItems)
{
   Treinen treinData = (Treinen)item;
   Debug.WriteLine(treinData.Name);
}

这里我从列表框中获取所选项目名称，其中包含大约60个名称，具体取决于我想要获取所选项的SQL数据的选择。我认为这需要附加一个动态的.Where子句。

   ObjectQuery<Fouten> fouten = eventsEntities.Foutens;

   loadedData =
   (from fout in fouten
   where datumStart <= fout.Datum && datumEnd >= fout.Datum

   .... here should where be extended in some way, for example:
   && foreach (var item in _listBox.SelectedItems)
   {
     Treinen treinData = (Treinen)item;
     where fout.Treinen.Name == treinData.Name
   }
   orderby fout.Datum, fout.Time

   select new
   {
      Datum = fout.Datum,
      Time = fout.Time,
      FoutCode = fout.FoutCode,
      Omschrijving = fout.Omschrijving,
      Teller = fout.Teller,
      Module = fout.Module.ToUpper(),
      FoutId = fout.FoutId,
      TreinId = fout.TreinId
   }).AsEnumerable().Select(x => new Fouten
   {
      Datum = x.Datum,
      Time = x.Time,
      FoutCode = x.FoutCode,
      Omschrijving = x.Omschrijving,
      Teller = x.Teller,
      Module = x.Module,
      FoutId = x.FoutId,
      TreinId = x.TreinId
   })
   .ToList();

显然，这并不起作用，但希望它对我想要完成的事情有意义。现在我获取所有项目的数据而不是所选项目的数据。任何人都知道如何解决？

Answer 1

我认为你的“Treinen”中有一个ID字段（或属性），因为你有你的fout.TreinId更容易找到ID。

您可以在进入查询之前填写您的ID列表，然后检查您的ID是否在列表中：

List<int> treinenIds = new List<int>();
foreach (var item in _listBox.SelectedItems)
    treinenIds.Add(((Treinen)item).Id);

ObjectQuery<Fouten> fouten = eventsEntities.Foutens;

loadedData =
(from fout in fouten

    where datumStart <= fout.Datum && datumEnd >= fout.Datum

    //where-clause
    where treinenIds.Contains(fout.TreinId)

orderby fout.Datum, fout.Time

select new
{
    Datum = fout.Datum,
    Time = fout.Time,
    FoutCode = fout.FoutCode,
    Omschrijving = fout.Omschrijving,
    Teller = fout.Teller,
    Module = fout.Module.ToUpper(),
    FoutId = fout.FoutId,
    TreinId = fout.TreinId
}).AsEnumerable().Select(x => new Fouten
{
    Datum = x.Datum,
    Time = x.Time,
    FoutCode = x.FoutCode,
    Omschrijving = x.Omschrijving,
    Teller = x.Teller,
    Module = x.Module,
    FoutId = x.FoutId,
    TreinId = x.TreinId
})
.ToList();

我不确定查询是否支持.Contains，但如果是，那么此代码应该适用于您的示例。

LINQ in c＃：foreq in linq

1 个答案: