如何在RollBack上捕获异常

Question

对catch子句中已存在的SqlTransaction RollBack实现错误处理的最佳方式是什么？我的代码大致是这样的：

using (SqlConnection objSqlConn = new SqlConnection(connStr)) { 
    objSqlConn.Open(); 

    using (SqlTransaction objSqlTrans = objSqlConn.BeginTransaction()) { 
    try { 
     // code 
     // more code 
     // and more code 
    } 
    catch (Exception ex) { 
     // What happens if RollBack() has an exception? 
     objSqlTrans.Rollback(); 
     throw ex; 
    } 
    } 
} 

我相信我的应用程序必须在try块，而这又被夹在catch块，然后回滚试图在一个例外。但是，我看到的错误说了一些关于SqlTransaction.ZombieCheck（）的问题，这让我怀疑RollBack（）本身是否也抛出了异常。那么，我需要在RollBack（）中实现某种类型的错误处理吗？我该怎么做，并设法保留将执行放入catch块的异常呢？

编辑 - 我的所有代码：

using (SqlConnection objSqlConn = new SqlConnection(connStr)) { 

    objSqlConn.Open(); 

    // Begin Transaction 
    using (SqlTransaction objSqlTrans = objSqlConn.BeginTransaction()) { 

     try { 
      // Create file in db (which in turn creates it on disk according to where the 
      // ...FileStream points) 
      SqlCommand objSqlCmd = new SqlCommand("usp_FileAdd", objSqlConn, objSqlTrans); 
      objSqlCmd.CommandType = CommandType.StoredProcedure; 

      // Sql parameter - report name 
      SqlParameter objSqlParam1 = new SqlParameter("@ObjectID", SqlDbType.Int); 
      objSqlParam1.Value = objID; 

      // Sql out parameter - returns the file path 
      SqlParameter objSqlParamOutput = new SqlParameter("@filepath", SqlDbType.VarChar, -1); 
      objSqlParamOutput.Direction = ParameterDirection.Output; 

      // Add Sql parameters to command obj 
      objSqlCmd.Parameters.Add(objSqlParam1); 
      objSqlCmd.Parameters.Add(objSqlParamOutput); 

      // Execute command object 
      objSqlCmd.ExecuteNonQuery(); 

      // Path to the FileStream 
      string path = objSqlCmd.Parameters["@filepath"].Value.ToString(); 

      // Reset command object to get FileStream 
      objSqlCmd = new SqlCommand(
       "SELECT GET_FILESTREAM_TRANSACTION_CONTEXT()", 
       objSqlConn, 
       objSqlTrans); 

      // Execute command object 
      Object obj = objSqlCmd.ExecuteScalar(); 

      if (obj != DBNull.Value) { 
       // Byte array representing the FileStream 
       byte[] fsBytes = (byte[])obj; 

       SqlFileStream sqlFS = new SqlFileStream(path, fsBytes, FileAccess.Write); 

       using (FileStream fs = fi.OpenRead()) { 
        //byte[] b = new byte[1024]; 
        byte[] b = new byte[4096]; 
        int read; 

        fs.Seek(0, SeekOrigin.Begin); 

        while ((read = fs.Read(b, 0, b.Length)) > 0) { 
         sqlFS.Write(b, 0, read); 
        } 
       } 

       sqlFS.Close(); 
      } 

      // Commit the transaction 
      objSqlTrans.Commit(); 
     } 
     catch (Exception ex) { 
      objSqlTrans.Rollback(); 
      throw ex; 
     } 
    } 
} 

Answer 1

你已经有了

using (SqlTransaction objSqlTrans = objSqlConn.BeginTransaction()) 

这将导致事务回滚时，如果它没有被COMMITED using块结束。

所以我会完全删除catch块。

至于回滚失败时会发生什么，我会首先认识到这是一个非常糟糕的情况，并遵循Eric Lippert关于类似问题的建议。 here

Answer 2

该片段应阅读像这样：

using (SqlConnection objSqlConn = new SqlConnection(connStr)) { 
objSqlConn.Open(); 

using (SqlTransaction objSqlTrans = objSqlConn.BeginTransaction()) { 
    try { 
    // code 
    // more code 
    // and more code 
    } 
    catch (Exception ex) { 
    // What happens if RollBack() has an exception? 
    try { 
     objSqlTrans.Rollback(); 
    } catch (Exception ex2) { 
     /* can't roll back -- db gone? db will do it for us since we didn't commit. */ 
    } 
    throw; 
    } 
} 
} 

编辑：试想想，它没有必要对整个try/catch语句在这种特殊情况下，由于关闭与未提交的事务的连接会回滚事务，因此该块可能如下所示：

using (SqlConnection objSqlConn = new SqlConnection(connStr)) { 
objSqlConn.Open(); 

using (SqlTransaction objSqlTrans = objSqlConn.BeginTransaction()) { 
    // code 
    // more code 
    // and more code 
} 
}