54

我正在创建一个项目，我需要在单个 SQL 连接中运行 2-3 个 SQL 命令。这是我写的代码：

SqlConnection con = new SqlConnection(@"Data Source=(LocalDB)\v11.0;AttachDbFilename=|DataDirectory|\project.mdf;Integrated Security=True");
con.Open();
SqlCommand cmd = new SqlCommand("select *  from " + mytags.Text + " ", con);
SqlDataReader rd = cmd.ExecuteReader();
if (rd.Read())
{
    con.Close();
    con.Open();
    SqlCommand cmd1 = new SqlCommand("insert into " + mytags.Text + " values ('fname.lname@gmail.com','" + TextBox3.Text + "','" + TextBox4.Text + "','" + TextBox5.Text + "','"+mytags.Text+"')", con);
    cmd1.ExecuteNonQuery();
    label.Visible = true;
    label.Text = "Date read and inserted";
}
else
{
    con.Close();
    con.Open();
    SqlCommand cmd2 = new SqlCommand("create table " + mytags.Text + " ( session VARCHAR(MAX) , Price int , Description VARCHAR(MAX), Date VARCHAR(20),tag VARCHAR(10))", con);
    cmd2.ExecuteNonQuery();
    con.Close();
    con.Open();
    SqlCommand cmd3 = new SqlCommand("insert into " + mytags.Text + " values ('" + Session + "','" + TextBox3.Text + "','" + TextBox4.Text + "','" + TextBox5.Text + "','" + mytags.Text + "')", con);
    cmd3.ExecuteNonQuery();
    label.Visible = true;
    label.Text = "tabel created";
    con.Close();
}

我试图消除错误，但我发现连接不会出现其他情况。请检查代码并建议是否有任何错误或任何其他解决方案。

4

9 回答 9

52

只需更改而不是每次都SqlCommand.CommandText创建一个新的。SqlCommand无需关闭并重新打开连接。

// Create the first command and execute
var command = new SqlCommand("<SQL Command>", myConnection);
var reader = command.ExecuteReader();

// Change the SQL Command and execute
command.CommandText = "<New SQL Command>";
command.ExecuteNonQuery();
于 2012-12-03T04:56:49.347 回答
34

以下应该工作。始终保持单个连接打开，只需创建新命令并执行它们。

using (SqlConnection connection = new SqlConnection(connectionString))
{
    connection.Open();
    using (SqlCommand command1 = new SqlCommand(commandText1, connection))
    {
    }
    using (SqlCommand command2 = new SqlCommand(commandText2, connection))
    {
    }
    // etc
}
于 2012-12-03T05:00:39.830 回答
34

Just enable this property in your connection string:

sqb.MultipleActiveResultSets = true;

This property allows one open connection for multiple datareaders.

于 2014-04-27T10:01:41.673 回答
12

我没有测试过，但主要思想是：在每个查询上加上分号。

SqlConnection connection = new SqlConnection();
SqlCommand command = new SqlCommand();
connection.ConnectionString = connectionString; // put your connection string
command.CommandText = @"
     update table
     set somecol = somevalue;
     insert into someTable values(1,'test');";
command.CommandType = CommandType.Text;
command.Connection = connection;

try
{
    connection.Open();
}
finally
{
    command.Dispose();
    connection.Dispose();
}

更新： 您可以关注 ADO.NET Command.CommandText 属性中是否可以有多个 SQL 指令？也

于 2012-12-03T05:16:37.707 回答
10

顺便说一句，这很可能是通过SQL注入攻击的。阅读并相应地调整您的查询是值得的。

也许甚至可以为此创建一个存储过程，并使用sp_executesql 之类的东西，当需要动态 sql 时（即未知表名等），它可以提供一些保护。有关更多信息，请查看此链接。

于 2012-12-03T05:11:48.540 回答
9

没有人提到这一点，但您也可以使用 ; 分隔您的命令。同一命令文本中的分号： 

using (SqlConnection conn = new SqlConnection(connString))
    {
        using (SqlCommand comm = new SqlCommand())
        {
                comm.Connection = conn;
                comm.CommandText = @"update table ... where myparam=@myparam1 ; " +
                                    "update table ... where myparam=@myparam2 ";
                comm.Parameters.AddWithValue("@myparam1", myparam1);
                comm.Parameters.AddWithValue("@myparam2", myparam2);
                conn.Open();
                comm.ExecuteNonQuery();

        }
    }
于 2020-04-16T15:18:31.750 回答
4

如果有人感兴趣，可以使用多个非查询示例。

using (OdbcConnection DbConnection = new OdbcConnection("ConnectionString"))
{
  DbConnection.Open();
  using (OdbcCommand DbCommand = DbConnection.CreateCommand())
  {
    DbCommand.CommandText = "INSERT...";
    DbCommand.Parameters.Add("@Name", OdbcType.Text, 20).Value = "name";
    DbCommand.ExecuteNonQuery();

    DbCommand.Parameters.Clear();
    DbCommand.Parameters.Add("@Name", OdbcType.Text, 20).Value = "name2";
    DbCommand.ExecuteNonQuery();
  }
}
于 2019-09-12T13:51:41.157 回答
3

在这里您可以找到 Postgre 示例，此代码在单个 SQL 连接中运行多个 sql 命令（更新 2 列）

public static class SQLTest
    {
        public static void NpgsqlCommand()
        {
            using (NpgsqlConnection connection = new NpgsqlConnection("Server = ; Port = ; User Id = ; " + "Password = ; Database = ;"))
            {
                NpgsqlCommand command1 = new NpgsqlCommand("update xy set xw = 'a' WHERE aa='bb'", connection);
                NpgsqlCommand command2 = new NpgsqlCommand("update xy set xw = 'b' where bb = 'cc'", connection);
                command1.Connection.Open();
                command1.ExecuteNonQuery();
                command2.ExecuteNonQuery();
                command2.Connection.Close();
            }
        }
    }
于 2017-12-20T09:20:39.607 回答
1 
using (var connection = new SqlConnection("Enter Your Connection String"))
    {
        connection.Open();
    
        using (var command = connection.CreateCommand())
        {
            command.CommandText = "Enter the First Command Here";
            command.ExecuteNonQuery();
    
            command.CommandText = "Enter Second Comand Here";
            command.ExecuteNonQuery();

    //Similarly You can Add Multiple
        }
    }

它对我有用。

于 2020-11-12T15:21:11.153 回答