C#中的DropDownList只获取数据库中第一个不同的行值

本文关键字：第一个 DropDownList 中的 获取 数据库 | 更新日期: 2023-09-27 17:58:40

这可能是一个小问题，但我真的不知道它发生在哪里。

我有一个由三列组成的表，名称为TaxRankID、TaxObjectID和TaxName。控制器中的代码如下：

    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，这个。ViewData["country"]运行良好，创建了这样的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走了，看起来和第一个完全一样，但产生了奇怪的结果。

    <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>

正如你所看到的，这些都是一样的。但我确信在数据库中它们是不一样的，

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。很明显，它只是选择TaxRankID的第一个值，这是不同的。

你知道为什么会发生这种事吗？

感谢您的帮助。

我通过使用纯SQL和DataTable成功地生成了正确的DropDownList，但我仍然很好奇为什么原始的会生成奇怪的结果。

如果有人需要，修改后的代码粘贴在下面，这要归功于Ryan VandenHubel在从DataTable 填充SelectList中的回答

        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");

C#中的DropDownList只获取数据库中第一个不同的行值

您可以这样更改查询：

    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();
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