为什么字符串IndexOf()不区分大小写? [英] why is string IndexOf() acting case-INsensitive?

问题描述

我真的为这个感到难过.我正在学习LINQ，并使用Microsoft Visual C#Express Edition连接到包含有关我的书籍信息的SQL Server数据库.我根据需要创建了LINQ to SQL类.这些东西显然有效.一切正常，但我无法确定自己的一生，为什么，如果我搜索"SR"(大写字母)，它会找到两条记录，即"SR-71 Revealed，The Inside Story"，正如预期的那样，但是还会发现褪色的太阳:Kesrith"，"sr"为小写.我正在使用字符串类的IndexOf()方法，该方法应该执行区分大小写的比较，对吗?输出显示如上所示的第二本书的书名，其中"sr"为小写.这是代码的相关部分:

I'm really stumped by this one. I'm learning LINQ and used Microsoft Visual C# Express Edition to connect to a SQL Server database containing information about my books. I created the LINQ to SQL classes as needed. That stuff obviously works. It all works except I cannot figure out for the life of me why, if I search for "SR" (uppercase), it finds two records, "SR-71 Revealed, The Inside Story", as expected, but it also finds "Faded Sun: Kesrith" where the "sr" is lowercase. I'm using the IndexOf() method of the string class, which is supposed to perform a case-SENSITIVE comparison, right? The output displays the second book title as shown above, with the "sr" in lowercase. Here's the pertinent part of the code:

// normal using directives here
namespace QueryBooksDB {
    class Program {
        static void Main() {
            var urgh = new BooksDataContext();

            Console.WriteLine("Enter a string to search for:");
            string str = Console.ReadLine();

            var list = from book in urgh.Books
                        where book.Title.IndexOf(str) > -1
                        orderby book.Title
                        select new { ID = book.BookId, book.Title, book.Location };

            foreach ( var b in list ) {
                Console.WriteLine(b.Title);
            }
        }
    }
}

推荐答案

在最后一步，您的查询将转换为sql.在SQL Server字符串中，类似的字段(varchar，nvarchar)不区分大小写.所以 select * from tbl where col like '%foo%'将检索值是Foo还是FOo

At the final step your query is translated into sql. In SQL server string alike fields (varchar, nvarchar) are case insensetive. So select * from tbl where col like '%foo%' will retrieve if the value is Foo or FOo

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