Question

这可能是一个小问题，但我真的无法找到它发生的位置。

我有一个包含三列的表，其名称为TaxRankID，TaxObjectID和TaxName。在控制器代码中是这样的：

    public ActionResult DefineFauna()
    {

        var cExtant = PredicateBuilder.True<FaunaPoliticalUnits>();
        cExtant = cExtant.And(r => r.PoliticalUnitLevel == 1);
        var results = from r in lw.PoliticalUnits.AsExpandable().Where(cExtant.Expand()).OrderBy(r => r.PoliticalUnitName)
                      select r;
        var selectList = new SelectList(results.ToList(), "GeogID", "PoliticalUnitName",5);
        this.ViewData["country"] = selectList;


        this.ViewData["tscope"] = ListHelp();

        return View();
    }

    private SelectList ListHelp()
    {
        var tsExtant = PredicateBuilder.True<FaunaTaxonomicScopes>();
        tsExtant = tsExtant.And(r => r.TaxRankID == 18 || r.TaxRankID == 17 || r.TaxRankID == 24);
        var tsresults = from r in lw.TaxonomicScopes.AsExpandable().Where(tsExtant.Expand()).OrderBy(r => r.TaxRankID).ThenBy(r => r.TaxName)
                        select r;
        var tsselectList = new SelectList(tsresults.ToList(), "TaxObjectID", "TaxName");
        return tsselectList;
    }

第一个，this.ViewData [＆＃34; country＆＃34;]工作正常，创建一个这样的DropDownList：

<select id="country" name="country" style="width: 300;">
<option value="162">Afghanistan</option>
<option value="103">Albania</option>
<option value="82">Algeria</option>
<option value="4118">Andorra</option>
<option value="157">Angola</option>

第二个，我甚至把它作为一个单独的函数移出来，看起来和第一个完全一样，但却产生了奇怪的结果。

    <select id="tscope" name="tscope" style="width: 300;"><option value="12996">Neuropterida (all)</option>
<option value="12933">Glosselytrodea only</option>
<option value="12933">Glosselytrodea only</option>
<option value="12933">Glosselytrodea only</option>
<option value="12933">Glosselytrodea only</option>
<option value="12933">Glosselytrodea only</option>
<option value="12790">Glosselytrodea : Archoglossopteridae only</option>
<option value="12790">Glosselytrodea : Archoglossopteridae only</option>
<option value="12790">Glosselytrodea : Archoglossopteridae only</option>
<option value="12790">Glosselytrodea : Archoglossopteridae only</option>
<option value="12790">Glosselytrodea : Archoglossopteridae only</option>
<option value="12790">Glosselytrodea : Archoglossopteridae only</option>
<option value="12790">Glosselytrodea : Archoglossopteridae only</option>
<option value="12790">Glosselytrodea : Archoglossopteridae only</option>
<option value="12790">Glosselytrodea : Archoglossopteridae only</option>
<option value="12790">Glosselytrodea : Archoglossopteridae only</option>
<option value="12790">Glosselytrodea : Archoglossopteridae only</option>
<option value="12790">Glosselytrodea : Archoglossopteridae only</option>
<option value="12790">Glosselytrodea : Archoglossopteridae only</option>
<option value="12790">Glosselytrodea : Archoglossopteridae only</option>
<option value="12790">Glosselytrodea : Archoglossopteridae only</option>
<option value="12790">Glosselytrodea : Archoglossopteridae only</option>
<option value="12790">Glosselytrodea : Archoglossopteridae only</option>
<option value="12790">Glosselytrodea : Archoglossopteridae only</option>
<option value="12790">Glosselytrodea : Archoglossopteridae only</option>
<option value="12790">Glosselytrodea : Archoglossopteridae only</option>
<option value="12790">Glosselytrodea : Archoglossopteridae only</option>
<option value="12790">Glosselytrodea : Archoglossopteridae only</option>
<option value="12790">Glosselytrodea : Archoglossopteridae only</option>
<option value="12790">Glosselytrodea : Archoglossopteridae only</option>
<option value="12790">Glosselytrodea : Archoglossopteridae only</option>
<option value="12790">Glosselytrodea : Archoglossopteridae only</option>
<option value="12790">Glosselytrodea : Archoglossopteridae only</option>
<option value="12790">Glosselytrodea : Archoglossopteridae only</option>
<option value="12790">Glosselytrodea : Archoglossopteridae only</option>
<option value="12790">Glosselytrodea : Archoglossopteridae only</option>
<option value="12790">Glosselytrodea : Archoglossopteridae only</option>
<option value="12790">Glosselytrodea : Archoglossopteridae only</option>
<option value="12790">Glosselytrodea : Archoglossopteridae only</option>
<option value="12790">Glosselytrodea : Archoglossopteridae only</option>
<option value="12790">Glosselytrodea : Archoglossopteridae only</option>
<option value="12790">Glosselytrodea : Archoglossopteridae only</option>
<option value="12790">Glosselytrodea : Archoglossopteridae only</option>
<option value="12790">Glosselytrodea : Archoglossopteridae only</option>
<option value="12790">Glosselytrodea : Archoglossopteridae only</option>
<option value="12790">Glosselytrodea : Archoglossopteridae only</option>
<option value="12790">Glosselytrodea : Archoglossopteridae only</option>
<option value="12790">Glosselytrodea : Archoglossopteridae only</option>
<option value="12790">Glosselytrodea : Archoglossopteridae only</option>
<option value="12790">Glosselytrodea : Archoglossopteridae only</option>
<option value="12790">Glosselytrodea : Archoglossopteridae only</option>
<option value="12790">Glosselytrodea : Archoglossopteridae only</option>
<option value="12790">Glosselytrodea : Archoglossopteridae only</option>
<option value="12790">Glosselytrodea : Archoglossopteridae only</option>
<option value="12790">Glosselytrodea : Archoglossopteridae only</option>
<option value="12790">Glosselytrodea : Archoglossopteridae only</option>
<option value="12790">Glosselytrodea : Archoglossopteridae only</option>
<option value="12790">Glosselytrodea : Archoglossopteridae only</option>
<option value="12790">Glosselytrodea : Archoglossopteridae only</option>
<option value="12790">Glosselytrodea : Archoglossopteridae only</option>
</select>

正如您所看到的，它们都是一样的。但我确信在数据库中它们并不相同，

TaxRankID   TaxObjectID TaxName
17  12996   Neuropterida (all)
18  12933   Glosselytrodea only
18  12922   Megaloptera only
18  12921   Neuroptera only
18  17137   Neuropterida, incertae sedis only
18  12923   Raphidioptera only
24  12790   Glosselytrodea : Archoglossopteridae only
24  12791   Glosselytrodea : Glosselytridae only
24  12380   Glosselytrodea : Jurinidae only
24  12262   Glosselytrodea : Permoberothidae only
24  12234   Megaloptera : Corydalidae only
24  12738   Megaloptera : Corydasialidae only
24  12280   Megaloptera : Euchauliodidae only
24  12911   Megaloptera : Nanosialidae only
24  12290   Megaloptera : Parasialidae only
24  12237   Megaloptera : Sialidae only
24  12811   Neuroptera : Aetheogrammatidae only

看起来像这样。而且很清楚，它只选择TaxRankID的第一个值不同。

有关为何发生这种情况的任何想法？

感谢任何帮助。

我设法通过使用纯SQL和DataTable生成正确的DropDownList，但是我仍然很好奇为什么原始的会产生奇怪的结果。

如果有人需要，修改后的代码会粘贴在下面，感谢Ryan VandenHeuvel在Populating a SelectList from a DataTable中的答案

        DataTable subjects = new DataTable();
        SqlConnection con = new SqlConnection(conString);
        SqlDataAdapter adapter = new SqlDataAdapter("SELECT TaxRankID, TaxObjectID, TaxName FROM  lacewing.dbo.tblLdlFaunaTaxonomicScopes ORDER BY TaxRankID, TaxName", con);
        adapter.Fill(subjects);
        List<SelectListItem> list = new List<SelectListItem>();
        foreach (DataRow row in subjects.Rows)
        {
            list.Add(new SelectListItem()
            {
                Text = row[2].ToString(),
                Value = row[1].ToString()
            });
        }

        return new SelectList(list, "Value", "Text");

Answer 1

您可以像这样更改查询：

    var ids=new List<int> {17,18,24};

    var results = lw.TaxonomicScopes.Join(ids, 
                  x => x.TaxRankID , 
                  y => y.TaxRankID , 
                 (x, y) => x)
                 .OrderBy(r => r.TaxRankID)
                 .ThenBy(r => r.TaxName)
                 .ToList();

C＃中的DropDownList只获取数据库中第一个不同的行值

1 个答案: