Dropping SQL Server database through C#

问题:

I am using this code to delete a database through C#

Int32 result = 0;

try
{
        String Connectionstring = CCMMUtility.CreateConnectionString(false, txt_DbDataSource.Text, "master", "sa", "happytimes", 1000);

        SqlConnection con = new SqlConnection();
        con.ConnectionString = Connectionstring;

        String sqlCommandText = "DROP DATABASE [" + DbName + "]";
        if (con.State == ConnectionState.Closed)
        {
            con.Open();
            SqlConnection.ClearPool(con);
            con.ChangeDatabase("master");
            SqlCommand sqlCommand = new SqlCommand(sqlCommandText, con);
            sqlCommand.ExecuteNonQuery();
        }
        else
        {
            con.ChangeDatabase("master");
            SqlCommand sqlCommand = new SqlCommand(sqlCommandText, con);
            sqlCommand.ExecuteNonQuery();
        }



        con.Close();
        con.Dispose();
        result = 1;
    }
    catch (Exception ex)
    {
        result = 0;
    }
    return result;

But I get an error

Database currently in use

Can anyone help?

回答1:

Try this:

String sqlCommandText = @"
ALTER DATABASE " + DbName + @" SET SINGLE_USER WITH ROLLBACK IMMEDIATE;
DROP DATABASE [" + DbName + "]";

Also make sure that your connection string defaults you to the master database, or any other database other than the one you're dropping!

As an aside, you really don't need all of that stuff around your queries. The ConnectionState will always start off Closed, so you don't need to check for that. Likewise, wrapping your connection in a using block eliminates the need to explicitly close or dispose the connection. All you really need to do is:

String Connectionstring = CCMMUtility.CreateConnectionString(false, txt_DbDataSource.Text, "master", "sa", "happytimes", 1000);

using(SqlConnection con = new SqlConnection(Connectionstring)) {
    con.Open();
    String sqlCommandText = @"
        ALTER DATABASE " + DbName + @" SET SINGLE_USER WITH ROLLBACK IMMEDIATE;
        DROP DATABASE [" + DbName + "]";
    SqlCommand sqlCommand = new SqlCommand(sqlCommandText, con);
    sqlCommand.ExecuteNonQuery();
}
result = 1;

回答2:

Here is how you do it using Entity Framework version 6

System.Data.Entity.Database.Delete(connectionString);

回答3:

You should take a look at SMO. These allow you to manage all aspects of SQL Server from code, including deleting of databases.

The database object has a Drop method to delete database.

回答4:

Create sqlconnection object for different database other than you want to delete.

sqlCommandText = "DROP DATABASE [DBNAME]";
sqlCommand = new SqlCommand(sqlCommandText , sqlconnection);
sqlCommand.ExecuteNonQuery();

回答5:

In this case i would recommend that you take the database offline first... that will close all connections and etc... heres an article on how to do it: http://blog.sqlauthority.com/2010/04/24/sql-server-t-sql-script-to-take-database-offline-take-database-online/

Microsoft clearly states that A database can be dropped regardless of its state: offline, read-only, suspect, and so on. on this MSDN article (DROP DATABASE (Transact-SQL))

回答6:

Connection pooling at a guess, use sql server's activity monitor to make sure though.

Pooling keeps connections to the database alive in a cache, then when you create a new one, if there's one in the cache it hands it back instead of instantiating a new one. They hang around for a default time, (2 minutes I think) if they don't get re-used in that time, then they killed off.

So as a first go connect straight to master, instead of using change database, as I suspect change database will simply swap connections in the pool.

Add a check routine for database in use (use a connection to master to do it!). You can force the database to be dropped anyway by first executing

ALTER DATABASE [MyDatabase] SET SINGLE_USER WITH ROLLBACK IMMEDIATE

again from the connection to master!

However everybody else using the db, will no longer like you at all...

回答7:

Just don't use DB name in connection string.

"Data Source=.\SQLEXPRESS;Integrated Security=True;"