返回单行 [英] Returning a single row

问题描述

我正在尝试从数据库返回一行：

I'm trying to return a single row from a database:

using (connection = new SqlConnection(ConfigurationManager.AppSettings["connection"]))
{
    using (command = new SqlCommand(@"select top 1 col_1, col_2 from table1", connection))
    {
        connection.Open();

        using (reader = command.ExecuteReader())
        {
            reader.Read();
            return reader["col_1"];
        }
    }
}

但是我得到了错误消息：

But I'm getting the following error message:

编译器错误消息：CS0266：无法将类型'object'隐式转换为'string'。存在显式转换（您是否缺少
强制转换？）

第90行：return reader [ col_1];

Compiler Error Message: CS0266: Cannot implicitly convert type 'object' to 'string'. An explicit conversion exists (are you missing a cast?)
Line 90: return reader["col_1"];

我确定我犯了一个非常明显的错误，但是我似乎找不到任何单行示例，我发现的所有示例都是使用的多个返回行while循环。

I'm sure I am making a really obvious mistake, but I can't seem to find any single row examples, all I examples I find are for multiple returned rows using a while loop.

推荐答案

reader [ col_1] 返回对象。

您想要类似 reader.GetString（reader .GetOrdinal（ col_1））。

编辑->我只想在此处添加一条注释，已经提出，选择顶部而没有 ORDER BY 可以根据架构更改和/或快乐地为您提供随机结果-全面扫描。

Edit -> I just wanted to add a note here that, in addition to the concerns others have raised, a SELECT TOP without an ORDER BY can give you random results based on schema changes and/or merry-go-round scans.

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