C# Don'；在完成读取之前，不要关闭SQL连接

我有下面的代码，它可以工作，但是只读取数据库的顶行，然后终止。数组应该包含3条数据，但它只包含一条

我认为这是因为它不是循环

你怎么说让代码继续运行直到没有更多的数据可以读取

SqlConnection conn1 = new SqlConnection(ssConnectionString);
conn1.Open();

SqlCommand command1 = conn1.CreateCommand();
command1.CommandText = "SELECT FeedURL FROM [dbo].[Feeds]";

rssFeeds.Add(command1.ExecuteScalar());

conn1.Close();

---

默认情况下，

ExecuteScalar（）

将只返回一个值。您需要创建一个

DataReader

，然后使用

command1循环遍历结果。默认情况下
ExecuteScalar（）
将只返回一个值。您需要创建一个
DataReader
，然后使用
command1.ExecuteReader（）
循环查看结果。您可以使用ExecuteReader解决您的问题。在这个示例中，我从MSDN获取的是使用using语句的连接，因为SqlConnection类有一些非托管资源。如果您对使用和终结器还有更多问题，请检查

如何使用ExecuteReader，您可以检查：

您可以使用ExecuteReader解决您的问题。在这个示例中，我从MSDN获取的是使用using语句的连接，因为SqlConnection类有一些非托管资源。如果您对使用和终结器还有更多问题，请检查

如何使用ExecuteReader，您可以检查：

试试这个：

//method to make this code reusable
//the returned data set is accessible even if the underlying connection is closed
//NB: that means data's held in memory; so beware of your resource usage
    public DataSet ExecuteSQLToDataSet(string ssConnectionString, string query, string name)
    {
        DataSet ds = new DataSet("Tables");
        using (SqlConnection conn1 = new SqlConnection(ssConnectionString))
        {
            conn1.Open();
            SqlDataAdapter sda = new SqlDataAdapter(query, objConn);
            sda.FillSchema(ds, SchemaType.Source, name);
            sda.Fill(ds, name);
        } //using statement will close and dispose the connection for you
        return ds;
    }


//example usage

    DataSet ds = ExecuteSQLToDataSet(ssConnectionString, "SELECT FeedURL FROM [dbo].[Feeds]", "Feeds"); //nb: name doesn't have to match table name; you can call it what you like; naming is useful if you wanted to add other result sets to the same data set

    //DataTable tblFeeds = ds.Tables["Feeds"]; //if you want to access the above query by name

    foreach (DataTable tbl in ds.Tables)
    {
        foreach (DataRow dr in tbl.Rows) //tblFeeds.Rows if you did that instead of looping through all tables
        {
            //Console.WriteLine(dr["FeedURL"].ToString()); //you can specify a named column
            Console.WriteLine(dr[0].ToString()); //or just use the index
        }
    }
    Console.WriteLine("Done");
    Console.ReadLine();

更多详细信息：
尝试以下操作：

//method to make this code reusable
//the returned data set is accessible even if the underlying connection is closed
//NB: that means data's held in memory; so beware of your resource usage
    public DataSet ExecuteSQLToDataSet(string ssConnectionString, string query, string name)
    {
        DataSet ds = new DataSet("Tables");
        using (SqlConnection conn1 = new SqlConnection(ssConnectionString))
        {
            conn1.Open();
            SqlDataAdapter sda = new SqlDataAdapter(query, objConn);
            sda.FillSchema(ds, SchemaType.Source, name);
            sda.Fill(ds, name);
        } //using statement will close and dispose the connection for you
        return ds;
    }


//example usage

    DataSet ds = ExecuteSQLToDataSet(ssConnectionString, "SELECT FeedURL FROM [dbo].[Feeds]", "Feeds"); //nb: name doesn't have to match table name; you can call it what you like; naming is useful if you wanted to add other result sets to the same data set

    //DataTable tblFeeds = ds.Tables["Feeds"]; //if you want to access the above query by name

    foreach (DataTable tbl in ds.Tables)
    {
        foreach (DataRow dr in tbl.Rows) //tblFeeds.Rows if you did that instead of looping through all tables
        {
            //Console.WriteLine(dr["FeedURL"].ToString()); //you can specify a named column
            Console.WriteLine(dr[0].ToString()); //or just use the index
        }
    }
    Console.WriteLine("Done");
    Console.ReadLine();

更多详细信息：
您需要
ExecuteReader（）
和循环。如果您有更多记录，则需要在
循环时将rssFeeds或datareader包装在
中。什么
ExecuteScalar
返回一个值或
null
T.S
仔细阅读注释。。SLaks和我所说的完全一样。。请不要混淆问题“rsfeed”是什么？您应该使用“Using”结构并加载数据集或数据表。您需要
ExecuteReader（）
和循环。如果您有更多记录，则需要将rssFeeds或datareader包装在
中，而
循环什么
ExecuteScalar
返回一个值或
null
T.S
仔细阅读注释。。SLaks和我所说的完全一样。。请不要混淆问题“rsfeed”是什么？您应该使用“Using”结构并加载一个数据集或数据表。这也适用于Op，前提是他理解最重要的读者。HasRows在遍历其余结果集之前先检查。。好例子+1如果Op了解最重要的读者，这也适用于Op。在遍历结果集的其余部分之前，请先检查行。。好例子+1同样，完成后，您可能希望使用adapt.dispose（）和DS.dispose（）处理SqlDataAdapter和Dataset。完成后，您可能希望使用adapt.dispose（）和DS.dispose（）处理SqlDataAdapter和Dataset
//method to make this code reusable
//the returned data set is accessible even if the underlying connection is closed
//NB: that means data's held in memory; so beware of your resource usage
    public DataSet ExecuteSQLToDataSet(string ssConnectionString, string query, string name)
    {
        DataSet ds = new DataSet("Tables");
        using (SqlConnection conn1 = new SqlConnection(ssConnectionString))
        {
            conn1.Open();
            SqlDataAdapter sda = new SqlDataAdapter(query, objConn);
            sda.FillSchema(ds, SchemaType.Source, name);
            sda.Fill(ds, name);
        } //using statement will close and dispose the connection for you
        return ds;
    }


//example usage

    DataSet ds = ExecuteSQLToDataSet(ssConnectionString, "SELECT FeedURL FROM [dbo].[Feeds]", "Feeds"); //nb: name doesn't have to match table name; you can call it what you like; naming is useful if you wanted to add other result sets to the same data set

    //DataTable tblFeeds = ds.Tables["Feeds"]; //if you want to access the above query by name

    foreach (DataTable tbl in ds.Tables)
    {
        foreach (DataRow dr in tbl.Rows) //tblFeeds.Rows if you did that instead of looping through all tables
        {
            //Console.WriteLine(dr["FeedURL"].ToString()); //you can specify a named column
            Console.WriteLine(dr[0].ToString()); //or just use the index
        }
    }
    Console.WriteLine("Done");
    Console.ReadLine();