如何使用SqlCommand返回多个结果集？

Question

我可以执行多个查询并返回执行SqlCommand一次的结果吗？

Answer 1

请参阅SqlDataReader.NextResult(从调用SqlCommand.ExecuteReader返回SqlDataReader ):

在读取批处理Transact-SQL语句的结果时,将数据读取器推进到下一个结果[set].

例:

string commandText = @"SELECT Id, ContactId
FROM dbo.Subscriptions;

SELECT Id, [Name]
FROM dbo.Contacts;";


List<Subscription> subscriptions = new List<Subscription>();
List<Contact> contacts = new List<Contact>();

using (SqlConnection dbConnection = new SqlConnection(@"Data Source=server;Database=database;Integrated Security=true;"))
{
    dbConnection.Open();
    using (SqlCommand dbCommand = dbConnection.CreateCommand())
    {
        dbCommand.CommandText = commandText;
        using(SqlDataReader reader = dbCommand.ExecuteReader())
        {
            while(reader.Read())
            {
                subscriptions.Add(new Subscription()
                {
                    Id = (int)reader["Id"],
                    ContactId = (int)reader["ContactId"]
                });
            }

            // this advances to the next resultset 
            reader.NextResult();

            while(reader.Read())
            {
                contacts.Add(new Contact()
                {
                    Id = (int)reader["Id"],
                    Name = (string)reader["Name"]
                });
            }
        }
    }
}

其他例子:

• C#多个结果集
• 使用SqlDataReader执行返回多个结果集的查询:SqlCommand选择«ADO.Net«C#/ CSharp教程

Answer 2

创建一个Stored Procedure有多个选择,并填写DataSet.

using (SqlConnection conn = new SqlConnection(connection))
{
    DataSet dataset = new DataSet();
    SqlDataAdapter adapter = new SqlDataAdapter();
    adapter.SelectCommand = new SqlCommand("MyProcedure", conn);
    adapter.SelectCommand.CommandType = CommandType.StoredProcedure;
    adapter.Fill(dataset);
    return dataset;
}

对于DataTable存储过程中的每个选择,返回的数据集将在其中包含一个Tables数组.

Answer 3

不管您使用临时文本查询还是存储过程，诸如“ dapper”之类的工具都使此操作非常容易。例如：

using(var multi = conn.QueryMultiple(sql, args))
{
    var customers = multi.Read<Customer>().AsList(); // first grid
    var regionName = multi.ReadFirstOrDefault<string>(); // second grid
    var addresses = multi.Read<Address>().AsList(); // third grid
    // todo: use those things
}

还可以通过的可选参数读取单个网格而无需进行缓冲（作为IEnumerable<T>读取器本身的开放空间）Read[<T>]。