Question

我有这样的代码：

using (var sqlConnection = new SqlConnection(connectionString))
{
  sqlConnection.Open();
  using (var sqlCommand = new SqlCommand(scriptText, sqlConnection))
  {
    sqlCommand.ExecuteNonQuery();
  }
}

我第一次调用它来创建一个数据库，然后我形成一个连接字符串到这个数据库并尝试做一些工作（Open工作正常并说连接实际上是为第二个连接打开的）。但我得到一个“现有连接被远程主机强行关闭”，我可以看到sql日志“无法找到数据库ID 9.数据库可能尚未激活或可能正在转换”。所以，实际上在作业完成之前ExecuteNonQuery返回。当然，我可以直接将其发送垃圾邮件，直到情况发生变化，但还有更好的方法可以让DB为工作做好准备吗？

Answer 1

这个完整的样本适合我。

它创建数据库，创建表，在表中放置一行。

不确定你的结果有什么问题。

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Data.SqlClient;

namespace GranadaCoder.PlaygroundConsole.SqlStuff
{
    public class SqlPlayground
    {

        public static void EntryPointStuff()
        {
            string databaseName = "MyFirstDatabaseABC";
            string connectionString = string.Empty;
            string commandText = string.Empty;
            int returnValue = 0;
            string msg = string.Empty;

            SqlConnectionStringBuilder builder = new SqlConnectionStringBuilder();
            builder["Initial Catalog"] = "master";
            builder["integrated Security"] = true;
            builder["Server"] = @"MyMachine\MyInstance";
            connectionString = builder.ConnectionString;


            commandText = string.Format("IF EXISTS (Select * from sys.databases where name = N'{0}') DROP DATABASE [{0}]", databaseName);
            returnValue = RunACommand(connectionString, commandText);
            msg = string.Format("'{0}', {1}", returnValue, commandText);
            Console.WriteLine(msg);

            commandText = string.Format("IF NOT EXISTS (Select * from sys.databases where name = N'{0}') CREATE DATABASE [{0}]", databaseName);
            returnValue = RunACommand(connectionString, commandText);
            msg = string.Format("'{0}', {1}", returnValue, commandText);
            Console.WriteLine(msg);

            /* Change the Catalog */
            builder["Initial Catalog"] = databaseName;
            connectionString = builder.ConnectionString;


            commandText = "if exists (select * from dbo.sysobjects where id = object_id(N'[dbo].[CodeCategory]') and OBJECTPROPERTY(id, N'IsUserTable') = 1)    BEGIN       DROP TABLE [dbo].[CodeCategory]     END ";
            returnValue = RunACommand(connectionString, commandText);
            msg = string.Format("'{0}', {1}", returnValue, commandText);
            Console.WriteLine(msg);

            commandText = "CREATE TABLE [dbo].[CodeCategory] (    CodeCategoryKey           [smallint] not null     , CodeCategoryName      varchar(64) not null  ) ";
            returnValue = RunACommand(connectionString, commandText);
            msg = string.Format("'{0}', {1}", returnValue, commandText);
            Console.WriteLine(msg);


            commandText = "INSERT INTO [dbo].[CodeCategory] (     CodeCategoryKey       , CodeCategoryName    ) Select 1001 , 'MyFirstCodeCategory' ";
            returnValue = RunACommand(connectionString, commandText);
            msg = string.Format("'{0}', {1}", returnValue, commandText);
            Console.WriteLine(msg);

            commandText = "Select Count(*) from [dbo].[CodeCategory]";
            returnValue = RunACommand(connectionString, commandText);
            msg = string.Format("'{0}', {1}", returnValue, commandText);
            Console.WriteLine(msg);

        }




        private static int RunACommand(string connectionString, string scriptText)
        {

            int returnValue = 0;

            using (var sqlConnection = new SqlConnection(connectionString))
            {
                sqlConnection.Open();
                using (var sqlCommand = new SqlCommand(scriptText, sqlConnection))
                {
                    returnValue = sqlCommand.ExecuteNonQuery();
                }
                sqlConnection.Close();
            }

            return returnValue;
        }






    }

}

这对我有用（没有例外）：

    static void Main(string[] args)
    {

        try
        {

            SqlPlayground.EntryPointStuff();

            Console.WriteLine("Press Enter after deleting the database in SSMS manually with 'Close Existing Connections' checked.");
            Console.ReadLine();

            SqlPlayground.EntryPointStuff();


        }
        catch (Exception ex)
        {
            Console.WriteLine(ex.Message);
        }


        Console.WriteLine("Pressing Enter To End");
        Console.ReadLine();

    }

Answer 2

如果您在创建后立即执行其他操作（例如更新数据库架构），您可能会注意到此问题。等待几秒似乎解决了这个问题。

//wait for database creation
Thread.Sleep(3000);

Answer 3

在我的情况下adding Thread.Sleep(...)有帮助，但 root 的原因是失败的连接被缓存并由方法SqlConnection.Open（）使用。有关此情况，请参阅answer for this question。 Clearing the pool with SqlConnection.ClearAllPools()有帮助。

为什么等待几秒钟也有帮助呢？似乎它足以通过计时器自动清除池。

等待创建数据库完成

3 个答案: