ASP-Net Core Sql命令并发问题

Question

The back end of my application runs on NetCore as a Web API. The front end can be considered unrelated.

Most of my application runs on Entity framework. However I've recently had to implement some custom filtering into one of our DB calls. This Db call is called up to 3 times at once when a page on the web UI is loaded.

I'm having issues with the following code, which is throwing the following error: System.InvalidOperationException: 'The connection was not closed. The connection's current state is open.' System.InvalidOperationException: 'The connection was not closed. The connection's current state is open.'

The code:

foreach (var filter in dbFilters)
{

    var cacheKey = $"matching_filters_id:{matchingConfigId}_filter:{filter.FilterFunctionName}";
    var ids = new List<int>();

    if (!_cache.TryGetValue(cacheKey, out ids))
    {
        ids = new List<int>();
        using (var conn = _dbContext.Database.GetDbConnection())
        {
            conn.Open();
            using (var command = conn.CreateCommand())
            {
                command.CommandText =
                    SqlHelper.BuildGetMatchingFilterIdsForIntersect(filter.FilterFunctionName);
                using (var result = command.ExecuteReader())
                {
                    while (!result.IsClosed && result.Read())
                    {
                        ids.Add((int) result["ItemId"]);
                    }
                }
            }
            conn.Close();
        }

        var cacheEntryOptions = new MemoryCacheEntryOptions()
            .SetSlidingExpiration(TimeSpan.FromSeconds(30));
        _cache.Set(cacheKey, ids, cacheEntryOptions);
    }

    // Joins filtered list against each filter to make the list smaller.
    firstFilter = firstFilter.Join(ids, o => o.SourceKey, id => id, (o, id) => o).ToArray();
}

What i'm attempting to do, is filter the list firstFilter which is a POCO containing a few properties. I'm attempting to filter this by joining it to one or more list of filtered ItemIds being returned from multiple different SQL queries. Not the most elegant solution but its what i have to work with.

What i understand to be happening is that as the client is calling this method more then once, the methods are executing concurrently, causing the DB connection to be opened twice at once, causing the connection to fail and the error to be thrown.

I've attempted to stop this from happening by removing the async keyword form my method: public JsonResult GetMatches(int matchingConfigId...... ) but without success. I've also tried to intorduce session into the application, which I've read might cause calls to the same method from one client 'session' to happen in sequence rather then concurrently. But this has not seemed to have any effect.

Of course i might be barking up the entirely wrong tree.. but I've been bashing my head against said tree for most of the day now and I've reached my limit. Any help would be greatly appreciated

Answer 1

因此，事实证明来自实体框架的变量dbFilters尚未使用ToList()或ToListAsync()进行解析，因此该调用与数据库的连接仍处于打开状态，从而导致上述调用一段代码失败。