如何构建C#控制台应用程序以有效使用IDisposable数据库资源？

Question

这是我为C#控制台应用程序设计的(非常简化以说明问题空间)设计.数据库连接实现IDisposable,此解决方案不允许using数据库连接对象.有人可以为控制台应用程序提出更正确的结构吗？这是我经常需要解决的问题.

class Program 
{
    SQLiteConnection sourceConnection;
    SQLiteConnection destinationConnection;

    static void Main(string[] args)
    {
        Program shell = new Program();

        // get connection strings from command line arguments
        string sourceConnectionString = shell.getConnectionString(args);
        string destinationConnectionString = shell.getConnectionString(args);

        // call non-static methods that use
        shell.setUpConnections(sourceConnectionString, destinationConnectionString);

        shell.doDatabaseWork();
    }

    private void setUpConnections(string sourceConnectionString, string destinationConnectionString)
    {
        sourceConnection = new SQLiteConnection(sourceConnectionString);
        destinationConnection = new SQLiteConnection(destinationConnectionString);
    }

    private void doDatabaseWork()
    {
        // use the connections here
    }
}

编辑:

有些人无法弄清楚为什么我要将它们作为成员变量.这是doDatabaseWork中的用例(有点伪问题):

foreach (Row sourceRow in DBResultSet)
{
  string sourceXml = sourceRow.Columns["MyColumnName"].Value;
  string destinationXML = transformUsingXSLT(sourceXml);
  writeToDestination(destinationXml);
}

看看我想如何在这个循环的生命周期中保持这些连接打开？

Answer 1

编写一个实现IDisposable的类怎么样？

在类构造函数中,您可以实例化数据库连接.

然后在IDisposable.Dispose方法中,编写用于关闭数据库连接的拆卸代码.

这是一个代码示例,用于演示我的意思:

public class DBWrapper : IDisposable
{
    public SqlConnection Connection1 { get; set; }
    public SqlConnection Connection2 { get; set; }

    public DBWrapper()
    {
        Connection1 = new SqlConnection();
        Connection1.Open();
        Connection2 = new SqlConnection();
        Connection2.Open();
    }
    public void DoWork()
    {
        // Make your DB Calls here
    }

    public void Dispose()
    {
        if (Connection1 != null)
        {
            Connection1.Dispose();
        }
        if (Connection2 != null)
        {
            Connection2.Dispose();
        }
    }
}

然后,从您的Program类的main方法中:

class Program
{
    static void Main(string[] args)
    {
        using (DBWrapper wrapper = new DBWrapper())
        {
            wrapper.DoWork();
        }
    }
}

Answer 2

我认为最好的解决方案是从 Program 类中提取主要逻辑。Program 类是主要工作的某种启动器。为 SqlConnections 提供包装器确实不是一个好主意，因为它们已经是托管资源，包装它们是多余的。因此我的解决方案如下所示：

class ProgramCore : IDisposable
{
    internal ProgramCore(string sourceConnectionString, string destinationConnectionString)
    {
        setUpConnections(sourceConnectionString, destinationConnectionString);
    }

    internal void Execute()
    {
        // do whatever you want
        doDatabaseWork();
        // do whatever you want
    }

    public void Dispose()
    {
        if (_sourceConnection != null)
            _sourceConnection.Dispose();
        if (_destinationConnection != null)
            _destinationConnection.Dispose();
    }

    private void setUpConnections(string sourceConnectionString, string destinationConnectionString)
    {
        _sourceConnection = new SQLiteConnection(sourceConnectionString);
        _destinationConnection = new SQLiteConnection(destinationConnectionString);
    }

    private void doDatabaseWork()
    {
        // use the connections here
    }

    private SQLiteConnection _sourceConnection;
    private SQLiteConnection _destinationConnection;
}

class Program
{
    static void Main(string[] args)
    {
        // get connection strings from command line arguments
        string sourceConnectionString = GetConnectionString(args);
        string destinationConnectionString = GetConnectionString(args);

        using (ProgramCore core = new ProgramCore(sourceConnectionString, destinationConnectionString))
        {
            core.Execute();
        }
    }

    static string GetConnectionString(string[] args)
    {
        // provide parsing here
    }
}