C# 从数据库MVC4的DropDownList中删除重复项

我想从数据库中获取数据并将其添加到DropDownList中，以便在搜索面板中选择一个项目，我想从列表中删除重复的项目一个作者，多本书。我该怎么办

List<string> authorname = new List<string>();

foreach (var item in DB.Books)
{
    authorname.Add(item.BookDetails.authorname.ToString());
}

ViewData["AuthorName"] = new SelectList(authorname);

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从数据库中选择唯一值后，使用唯一值填充DropDownList。在SQL查询中使用“distinct”关键字以实现此目标

SELECT DISTINCT column_name,column_name
FROM table_name;

试试下面

List<string> authorname = new List<string>();

foreach (var item in DB.Books)
{
   if(!authorname.Contains(item.BookDetails.authorname.ToString()))
      authorname.Add(item.BookDetails.authorname.ToString());
}

ViewData["AuthorName"] = new SelectList(authorname);

---

您可以直接使用linq并获取不同的项

代码在这里

list<string> authorNamesDistinct = (from a in DB.Books
select a.BookDetails.authorname).Distinct().ToList();


ViewData["AuthorName"] = new SelectList(authorNamesDistinct);

list<string> authorNamesDistinct = (from a in DB.Books
select a.BookDetails.authorname).Distinct().ToList();


ViewData["AuthorName"] = new SelectList(authorNamesDistinct);