在C＃中执行异步触发时省略await语句并使用ado.net忘记写入数据库是否安全？ [英] Is it safe in C# to omit await statement when doing an async fire and forget write to a database with ado.net

问题描述

在asp.net应用程序中，我想尽可能高效地登录到数据库。我正在使用基本的ADO.NET来写入日志数据库，并且我想异步执行此操作，所以这是我要做的事情：

In an asp.net application I want to log to a database as efficiently as possible. I am using basic ADO.NET to write to the logging database and I want to do this async, so here is what I do:

        using (var conn = new SqlConnection(_connectionString)) {
            using (var cmd = new SqlCommand("INSERT INTO dbo.Logs (TimeStamp,ThreadId,Level,Message,Exception) VALUES (@TimeStamp,@ThreadId,@Level,@Message,@Exception)", conn)) {
                cmd.Parameters.AddWithValue("@TimeStamp", DateTime.UtcNow);
                cmd.Parameters.AddWithValue("@ThreadId", Thread.CurrentThread.ManagedThreadId);
                cmd.Parameters.AddWithValue("@Level", level);
                cmd.Parameters.AddWithValue("@Message", msg);
                cmd.Parameters.AddWithValue("@Exception", ex == null ? "" : ex.ToString());
                conn.Open();
                cmd.ExecuteNonQueryAsync();
            }
        }

现在我的问题是我是否应该等待cmd.ExecuteNonQueryAsync（）语句，或者如果可以省略await也是可以的，因为我基本上只需要执行即弃操作即可。

Now my question is if I should do an await on the cmd.ExecuteNonQueryAsync() statement or if it is ok to omit the await because I basically just need to do a fire-and-forget.

推荐答案

仅触发并忘记异步操作是不正确的-它可能会因异常而失败，并且您几乎肯定会在这种情况下要做一些事情（通知用户/重试/炸毁）。 （此外，如果有人使用特定的选项，则任务中的异常最终将导致进程中断。）

It is not OK to just fire and forget the async operation - it might fail with an exception, and you nearly certainly want to do something (notify the user/retry/blow up) in that case. (Besides, if someone uses a specific option, an exception in the task will eventually bring down the process).

另外：谁负责关闭连接？

Also: Who is responsible for closing the connection?

编辑：为了更清楚地说明连接关闭的问题，我将使用 try / finally （我知道这不是完全相同的IL，但是它足够接近以查看问题出在哪里）-在这种情况下，代码大致变为：

Edit: In order to make the problem of connection closing clearer, I will rewrite the using statements with try/finally (I know it is not the exact same IL, but it is close enough to see where the problem is) - in that case, the code roughly becomes:

SqlConnection conn;
try {
    conn = new SqlConnection("connString");
    SqlCommand cmd;
    try {
        cmd = new SqlCommand("INSERT INTO dbo.Logs (TimeStamp,ThreadId,Level,Message,Exception) VALUES (@TimeStamp,@ThreadId,@Level,@Message,@Exception)", conn);
        cmd.AddParameters();
        conn.Open();
        cmd.ExecuteNonQueryAsync();
    } finally {
        if (cmd != null) cmd.Dispose();
 } finally {
    if (conn != null) conn.Close();
 }

您可以看到 cmd.Dispose（）在 cmd.ExecuteNonQueryAsync（）之后被调用。那怎么行？我看到两种可能性：

You can see that cmd.Dispose() is called right after cmd.ExecuteNonQueryAsync(). How can that work? I see two possibilities:

1. cmd.Dispose（）（根据设计或事故）直到 cmd.ExecuteNonQueryAsync 能够完成其工作后才返回-这意味着您实际上仅从 cmd.Dispose 在 cmd.ExecuteNonQueryAsync 之后；在这种情况下，代码可以工作，但是您不能从await / async中受益；


2. 或 cmd.Dispose（）被执行阻止 cmd.ExecuteNonQueryAsync（）完成的方式；在这种情况下，代码将无法正常工作；

1. Either cmd.Dispose() (by design or accident) does not return until cmd.ExecuteNonQueryAsyncwas able to do its work - meaning that you actually only return from cmd.Dispose after cmd.ExecuteNonQueryAsync; in that case, the code works, but you do not benefit from await/async;
2. Or cmd.Dispose() is executed in a way that prevents cmd.ExecuteNonQueryAsync() from completing; in that case the code does not work;

在两种情况下，程序都是错误的-您需要等待或对任务调用 Wait（）以确保其行为正确。

In both cases, the program is wrong - you need either await or to call Wait() on the task in order to ensure that it behaves correctly.

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