問題描述

我正在嘗試使用 async/await 將一些記錄插入到數(shù)據(jù)庫中.如果我不手動打開連接，我會收到 Exception.如果我添加一些代碼來打開連接，那么一切正常.

這是當(dāng)前代碼(拋出異常):

using (var connection = new SqlConnection(ConnectionString)){var tasks = new List();sellUrls.ForEach(url => tasks.Add(InsertUrlAsync(connection, url)));rentUrls.ForEach(url => tasks.Add(InsertUrlAsync(connection, url)));等待 Task.WhenAll(tasks);}...私有異步任務(wù) InsertUrlAsync(IDbConnection 連接，字符串 url){const string query = "INSERT INTO ..";return await connection.ExecuteAsync(query, new { .. });}

異常:

消息:System.InvalidOperationException:操作無效.連接已關(guān)閉.

但是當(dāng)我將代碼更改為以下內(nèi)容時，它起作用了:

var tasks = new List();等待 connection.OpenAsync();sellUrls.ForEach(....) .. 等等...

類似的問題:

• Task.WhenAll，連接正在關(guān)閉
• SqlConnection 在 using 語句中意外關(guān)閉

Dapper 為您打開連接；但它也會在工作完成后關(guān)閉它.

現(xiàn)在，您正在使用一個連接運行兩個獨立的 async 任務(wù).

soldUrls.ForEach(url => tasks.Add(InsertUrlAsync(connection, url)));rentUrls.ForEach(url => tasks.Add(InsertUrlAsync(connection, url)));

兩個任務(wù)同時運行.當(dāng)一項任務(wù)的工作完成時，它關(guān)閉連接.但是其他任務(wù)仍在運行，它不再有權(quán)訪問打開的連接，因此出現(xiàn)了您提到的異常.

如您所說，如果您自己打開連接，Dapper 不會關(guān)閉它，一切正常.

順便說一下，在并發(fā)使用連接實例時，可能會出現(xiàn)意想不到的問題.請參閱此問題了解更多詳情.

I'm trying to use async/await to insert a number of records into a database. If I don't manually open the connection, I get an Exception. If I add some code to open the connection, then everything works ok.

Here's the current code (which throws an Exception):

using (var connection = new SqlConnection(ConnectionString))
{
    var tasks = new List<Task>();
    soldUrls.ForEach(url => tasks.Add(InsertUrlAsync(connection, url))); 
    rentUrls.ForEach(url => tasks.Add(InsertUrlAsync(connection, url)));
    await Task.WhenAll(tasks);
}

...

private async Task InsertUrlAsync(IDbConnection connection, string url)
{
    const string query = "INSERT INTO ..";
    return await connection.ExecuteAsync(query, new { .. });
}

the exception:

Message: System.InvalidOperationException : Invalid operation. The connection is closed.

but when I change the code to the following, it works:

var tasks = new List<Task>();
await connection.OpenAsync();
soldUrls.ForEach(....) .. etc ... 

Similar SO questions:

• Task.WhenAll, connection is closing
• SqlConnection closes unexpectedly inside using statement

Dapper opens the connection for you; but it also closes it when work is done.

Now, you are running two independent async tasks using one single connection.

soldUrls.ForEach(url => tasks.Add(InsertUrlAsync(connection, url))); 
rentUrls.ForEach(url => tasks.Add(InsertUrlAsync(connection, url)));

Both the tasks are running simultaneously. When work of one task finish, it closes the connection. But other task is still running which does not have access to open connection anymore and hence the exception you mentioned in question.

As you said, if you open the connection yourself, Dapper does not close it and everything just works fine.

By the way, while using connection instance concurrently, there may be unexpected issues. Please refer to this question for more details.

這篇關(guān)于為什么我需要手動打開這個 .NET Core 數(shù)據(jù)庫連接，而通常 Dapper 會自動打開它?的文章就介紹到這了，希望我們推薦的答案對大家有所幫助，也希望大家多多支持html5模板網(wǎng)！