c# - MySQL "network-related or instance-specific error occurred while establishing a connection to SQL Server"

Question

我一直在寻找这个问题的解决方案，唯一可能提供解决方案的是我唯一没有尝试过的解决方案，因为它涉及更改系统属性。如果可以的话，我想避免这种情况。

连接字符串正确，但还是连接不上。

异常发生在第30行，也就是打开连接字符串的地方。 conn.Open()

代码如下:

using System.Text;
using System.Data.SqlClient;

namespace My_Sql_Program
{
    class Program
    {
        static void Main()
        {
            try
            {
                // Step 1: Create a SqlConnection Object to connect to the 
                // SQL Northwind database.
                SqlConnection conn = new SqlConnection("server=localhost;database=dcim;uid=root;pwd=LlmD62jL");

                // Step 2: Create a SqlCommand object.
                SqlCommand cmd = conn.CreateCommand();

                // Step 3: Set the CommandText property of the SqlCommand object to a 
                // SQL SELECT statment that retrieves a row from the Customers table.
                cmd.CommandText = "SELECT UserName, UserPassword, AuthorityLevel, " +
                    "FROM Users " +
                    "WHERE UserName = 'ben'";

                // Step 4: Open the database connection using the 
                // Open() method of the SqlConnection object.
                conn.Open();

                //Step 5: Create a SqlDataReader object and call the ExecuteReader()
                //Method of the SqlCommand object to run the SELECT statement.
                SqlDataReader rdr = cmd.ExecuteReader();

                // Step 6: Read the row from the SqlDataReader object using the Read() method.
                rdr.Read();

                // Step 7: Display the column values.
                Console.WriteLine("rdr[\"UserName\"] = " + rdr["UserName"]);
                Console.WriteLine("rdr[\"UserPassword\"] = " + rdr["UserPassword"]);
                Console.WriteLine("rdr[\"AuthorityLevel\"] = " + rdr["AuthorityLevel"]);

                // Step 8: Close the SqlReader object using the Close() method.
                rdr.Close();

                // Step9: Close the SqlConnection object using the Close() method.
                conn.Close();
            }
            catch (SqlException e) 
            {
                Console.WriteLine("An SqlException was thrown.");
                Console.WriteLine("Number = " + e.Number);
                Console.WriteLine("Message = " + e.Message);
                Console.WriteLine("StackTrace:\n" + e.StackTrace);
            }
            Console.ReadLine();
        }
    }
}

当我运行它时，大约 30 秒没有任何反应，然后打印了 SqlException:

An SqlException was thrown.
Number = 2
Message = A network-related or instance-specific error occurred while establishing a connection
to SQL Server. The server was not found or was not accessible. Verify that the instance name is
correct and that SQL Server is configured to allow remote connections. (provider: Named Pipes
Provider, error: 40 - Could not open a connection to SQL Server)

StackTrace:
   at System.Data.SqlClient.SqlInternalConnection.OnError(SqlException exception, Boolean
breakConnection, Action`1 wrapCloseInAction)
   at System.Data.SqlClient.SqlInternalConnection.OnError(SqlException exception, Boolean
breakConnection, Action`1 wrapCloseInAction)
   at System.Data.SqlClient.TdsParser.ThrowExceptionAndWarning(TdsParserStateObject stateObj,
Boolean callerHasConnectionLock, Boolean asyncClose)
   at System.Data.SqlClient.TdsParser.Connect(ServerInfo serverInfo, SqlInternalConnectionTds
connHandler, Boolean ignoreSniOpenTimeout, Int64 timerExpire, Boolean encrypt, Boolean
trustServerCert, Boolean integratedSecurity, Boolean withFailover)
   at System.Data.SqlClient.SqlInternalConnectionTds.AttemptOneLogin(ServerInfo serverInfo, String
newPassword, SecureString newSecurePassword, Boolean ignoreSniOpenTimeout, TimeoutTimer timeout,
Boolean withFailover)
   at System.Data.SqlClient.SqlInternalConnectionTds.LoginNoFailover(ServerInfo serverInfo, String
newPassword, SecureString newSecurePassword, Boolean redirectedUserInstance, SqlConnectionString
connectionOptions, SqlCredential credential, TimeoutTimer timeout)
   at System.Data.SqlClient.SqlInternalConnectionTds.OpenLoginEnlist(TimeoutTimer timeout,
SqlConnectionString connectionOptions, SqlCredential credential, String newPassword, SecureString
newSecurePassword, Boolean redirectedUserInstance)
   at System.Data.SqlClient.SqlInternalConnectionTds..ctor(DbConnectionPoolIdentity identity,
SqlConnectionString connectionOptions, SqlCredential credential, Object providerInfo, String
newPassword, SecureString newSecurePassword, Boolean redirectedUserInstance, SqlConnectionString
userConnectionOptions)
   at System.Data.SqlClient.SqlConnectionFactory.CreateConnection(DbConnectionOptions options,
DbConnectionPoolKey poolKey, Object poolGroupProviderInfo, DbConnectionPool pool, DbConnection
owningConnection, DbConnectionOptions userOptions)
   at System.Data.ProviderBase.DbConnectionFactory.CreatePooledConnection(DbConnectionPool pool,
DbConnectionOptions options, DbConnectionPoolKey poolKey, DbConnectionOptions userOptions)
   at System.Data.ProviderBase.DbConnectionPool.CreateObject(DbConnectionOptions userOptions)
   at System.Data.ProviderBase.DbConnectionPool.UserCreateRequest(DbConnectionOptions userOptions)
   at System.Data.ProviderBase.DbConnectionPool.TryGetConnection(DbConnection owningObject, UInt32
waitForMultipleObjectsTimeout, Boolean allowCreate, Boolean onlyOneCheckConnection,
DbConnectionOptions userOptions, DbConnectionInternal& connection)
   at System.Data.ProviderBase.DbConnectionPool.TryGetConnection(DbConnection owningObject,
TaskCompletionSource`1 retry, DbConnectionOptions userOptions, DbConnectionInternal& connection)
   at System.Data.ProviderBase.DbConnectionFactory.TryGetConnection(DbConnection owningConnection,
TaskCompletionSource`1 retry, DbConnectionOptions userOptions, DbConnectionInternal& connection)
   at System.Data.ProviderBase.DbConnectionClosed.TryOpenConnection(DbConnection outerConnection,
DbConnectionFactory connectionFactory, TaskCompletionSource`1 retry, DbConnectionOptions
userOptions)
   at System.Data.SqlClient.SqlConnection.TryOpen(TaskCompletionSource`1 retry)
   at System.Data.SqlClient.SqlConnection.Open()
   at My_Sql_Program.Program.Main() in c:\users\paul\documents\visual studio 2010\Projects\My Sql
Program\My Sql Program\Program.cs:line 30

Answer 1

SqlConnection 用于 SqlServer。要连接到 MySql，您需要下载一些 drivers并在您的项目中引用它，并改用 MySqlConnection。

看看这个question还有这个CodeProject sample .