Question

我想从数据库中获取数据并将其添加到DropDownList以便在搜索面板中选择项目，我想从列表中删除重复项目（一位作者，多本书籍）。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);

Answer 1

在从数据库中选择DropDownList后，使用唯一值填充DropDownList。使用＆＃39; distinct＆＃39; SQL查询中的关键字是为了实现这一目标。

SELECT DISTINCT column_name,column_name
FROM table_name;

http://www.w3schools.com/sql/sql_distinct.asp

Answer 2

尝试以下

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);

Answer 3

List<string> authorname = new List<string>();
foreach (string name in DB.Books.Select(x=> new {name = x.authorname}).Distinct())
{
   authorname.Add(name);
}

Answer 4

你可以直接使用linq并获取不同的项目..

代码

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


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

从数据库MVC4中删除DropDownList中的重复项

4 个答案: