ALTER DB error when the connection string has an instance name - C# 4.0 - sql

Question

I have a service written in C# that runs under the domain admin account. This account is set as SQL admin on all the SQL Servers in that domain. The service needs to copy a mdf/ldf (SQL server 2003 or 2008) from one server to another and attach it to the new server. Instead of detaching the DB at the source server, I am changing the DB status to read only, and then copying the mdf/ldf files. Once they get copied over, I reset the DB status to read-write.
This is working if the source server name is something like MYSQLSERVER2K8. However, the code does not work if it is an instance name. For example: MYSQLSERVER2K8\VAULT. I have run the unit tests in NUnit on my code and the unit tests pass for both cases. However, the service is unable to change the DB status. The error we get is as follows:
SQL: ALTER DATABASE My_Test_DataBase SET SINGLE_USER WITH ROLLBACK IMMEDIATE ---> System.Data.SqlClient.SqlException: Database 'My_Test_DataBase' does not exist. Check sysdatabases. ALTER DATABASE statement failed. at System.Data.SqlClient.SqlConnection.
Here is my code (note that I am converting the server name to the IP address in the connection string. For example: MYSQLSERVER2K8\VAULT gets converted to 111.111.111.111\VAULT:
#region ChangeDatabaseStatus
/// <summary>
/// Change the database status to read-only/read-write
/// </summary>
/// <param name="serverName"></param>
/// <param name="databaseName"></param>
/// <param name="status"></param>
public virtual bool ChangeDatabaseStatus(string serverName, string databaseName, string status)
{
DateTime beginTimeStamp = DateTime.Now;
string sql = String.Empty;
bool databaseStatusChanged = false;
try
{
SqlConnection connection = GetSqlConnection(false);
string connectionString = connection.ConnectionString;
string serverIPAddress = Dns.GetHostAddresses(serverName.Contains(#"\") ? serverName.Substring(0, serverName.IndexOf(#"\")) : serverName)[0].ToString();
connectionString = connectionString.Replace("{0}", serverIPAddress = serverName.Contains(#"\") ? serverIPAddress + serverName.Substring(serverName.IndexOf(#"\"), serverName.Length - serverName.IndexOf(#"\")) : serverIPAddress);
connection.Close();
connection = new SqlConnection(connectionString);
using (SqlCommand command = new SqlCommand())
{
command.Connection = connection;
command.CommandTimeout = _commandTimeout;
command.CommandType = CommandType.Text;
command.CommandText = String.Format("ALTER DATABASE {0} SET SINGLE_USER WITH ROLLBACK IMMEDIATE", databaseName);
//Debugging & Exception handling
sql = HelperFunctions.BuildSQL(command);
connection.Open();
command.ExecuteNonQuery();
connection.Close();
}
using (SqlCommand command = new SqlCommand())
{
command.Connection = connection;
command.CommandTimeout = _commandTimeout;
command.CommandType = CommandType.Text;
command.CommandText = status == "ReadOnly" ? String.Format("ALTER DATABASE {0} SET READ_ONLY", databaseName) : String.Format("ALTER DATABASE {0} SET READ_WRITE", databaseName);
//Debugging & Exception handling
sql = HelperFunctions.BuildSQL(command);
connection.Open();
command.ExecuteNonQuery();
connection.Close();
databaseStatusChanged = true;
}
using (SqlCommand command = new SqlCommand())
{
command.Connection = connection;
command.CommandTimeout = _commandTimeout;
command.CommandType = CommandType.Text;
command.CommandText = String.Format("ALTER DATABASE {0} SET MULTI_USER", databaseName);
//Debugging & Exception handling
sql = HelperFunctions.BuildSQL(command);
connection.Open();
command.ExecuteNonQuery();
connection.Close();
}
}
catch (Exception e)
{
throw new DataProviderException(String.Format("{0} operation failed. SQL: {1}", MethodBase.GetCurrentMethod().Name, sql), e);
}
finally
{
LogPerformance(String.Format("Elapsed time for: {0}", MethodBase.GetCurrentMethod().Name), beginTimeStamp, DateTime.Now, null);
}
return databaseStatusChanged;
}
#endregion //ChangeDatabaseStatus

Answer 1

Check you don't have an alias configured.
Load the Sql Server Configuration Manager, under Native Client, then Aliases.
As Tony Hopkinson says, test you can connect using sqlcmd or something from the same machine:
sqlcmd -S MYSQLSERVER2K8\VAULT -q "ALTER DATABASE dbname SET SINGLE_USER WITH ROLLBACK IMMEDIATE"