Question

我有一个IDbConnection实例，它可以是任何连接，Sql，OleDb等。我想制作一个通用的包装器，这样我就可以给包装器发送一个连接，并获得一组很好的方法来方便操作。我有一个Query方法，我希望它返回一个DataTable，所以我可以做

IDataAdapter adapter = new OleDbDataAdapter();
adapter.SelectCommand = myCommand;
DataSet ds = new DataSet();
adapter.Fill(ds);

问题是我必须使用OleDbAdapter并且它不适用于SQL，我真的不想编写“特定于驱动程序”的代码。有没有办法从我的实例化IDbConnection对象中获取IDataAdapter实例？我知道我可以创建一个命令

IDbCommand command = _connection.CreateCommand();

认为必须有一些简单的方法来对IDataAdapter做同样的事情是合乎逻辑的。

编辑：

using (var reader = command.ExecuteReader())
{
    var dataTable = new DataTable();
    dataTable.Load(reader);
}

不完全是我要求的，但是一个很好的解决方案。

Answer 1

以下是如何使用反射获取适配器的粗略示例。

IDataAdapter GetAdapter(IDbConnection connection) {
    var assembly = connection.GetType().Assembly;
    var @namespace = connection.GetType().Namespace;    

    // Assumes the factory is in the same namespace
    var factoryType = assembly.GetTypes()
                        .Where (x => x.Namespace == @namespace)
                        .Where (x => x.IsSubclassOf(typeof(DbProviderFactory)))
                        .Single();

    // SqlClientFactory and OleDbFactory both have an Instance field.
    var instanceFieldInfo = factoryType.GetField("Instance", BindingFlags.Static | BindingFlags.Public);
    var factory = (DbProviderFactory) instanceFieldInfo.GetValue(null);

    return factory.CreateDataAdapter();
}

Answer 2

我遇到了同样的问题。这就是我解决它的方式

private DataSet executeDataQuery(string query, string connection, string provider, out Exception ex) {
        DataSet ds = new DataSet();
        ex = null;
        DbProviderFactory dbFactory = DbProviderFactories.GetFactory(provider);
        IDbConnection dbConnection = dbFactory.CreateConnection();
        dbConnection.ConnectionString = connection;
        using (dbConnection) {
            try {
                IDbDataAdapter dbAdapter = dbFactory.CreateDataAdapter();
                IDbCommand dbCommand = dbConnection.CreateCommand();
                dbCommand.CommandText = query;
                dbCommand.CommandType = CommandType.Text;
                dbAdapter.SelectCommand = dbCommand;
                dbAdapter.Fill(ds);
            }
            catch (Exception exc) {
                ex = exc;
            }
            finally {
                if (dbConnection.State == ConnectionState.Open) {
                    dbConnection.Close();
                }
            }
        }
        return ds;
    }

从IDbConnection实例实例化IDataAdapter

2 个答案: