我有这个查询,我在这个函数中得到错误:
var accounts = from account in context.Accounts
from guranteer in account.Gurantors
select new AccountsReport
{
CreditRegistryId = account.CreditRegistryId,
AccountNumber = account.AccountNo,
DateOpened = account.DateOpened,
};
return accounts.AsEnumerable()
.Select((account, index) => new AccountsReport()
{
RecordNumber = FormattedRowNumber(account, index + 1),
CreditRegistryId = account.CreditRegistryId,
DateLastUpdated = DateLastUpdated(account.CreditRegistryId, account.AccountNumber),
AccountNumber = FormattedAccountNumber(account.AccountType, account.AccountNumber)
})
.OrderBy(c=>c.FormattedRecordNumber)
.ThenByDescending(c => c.StateChangeDate);
public DateTime DateLastUpdated(long creditorRegistryId, string accountNo)
{
return (from h in context.AccountHistory
where h.CreditorRegistryId == creditorRegistryId && h.AccountNo == accountNo
select h.LastUpdated).Max();
}
错误是: …
我正在使用实体框架,偶尔我会得到这个错误.
EntityCommandExecutionException
{"There is already an open DataReader associated with this Command which must be closed first."}
at System.Data.EntityClient.EntityCommandDefinition.ExecuteStoreCommands...
即使我没有做任何手动连接管理.
这个错误间歇性地发生.
触发错误的代码(为了便于阅读而缩短):
if (critera.FromDate > x) {
t= _tEntitites.T.Where(predicate).ToList();
}
else {
t= new List<T>(_tEntitites.TA.Where(historicPredicate).ToList());
}
使用Dispose模式以便每次都打开新连接.
using (_tEntitites = new TEntities(GetEntityConnection())) {
if (critera.FromDate > x) {
t= _tEntitites.T.Where(predicate).ToList();
}
else {
t= new List<T>(_tEntitites.TA.Where(historicPredicate).ToList());
}
}
仍有问题
如果连接已经打开,EF为什么不重用连接？
关于为什么这可能会破裂的任何想法？
foreach (var p in pp)
{
ProjectFiles projectFile = (ProjectFiles)p;
projectFile.Status = Constants.ProjectFiles_ERROR;
projectFile.DateLastUpdated = DateTime.Now;
context.SaveChanges();
}
我读到问题的解决方法是在foreach循环之前一次性检索结果.
但我不这样做吗？"pp"是我案例中的结果集合
我正在处理一个非常大的数据集,大约有200万条记录.我有下面的代码,但是在它处理了三个批次,大约600,000条记录后得到了一个内存不足的例外.我理解,因为它循环遍历每个批处理实体框架的延迟加载,然后尝试将完整的200万条记录构建到内存中.有没有办法卸载我处理过的批次？
ModelContext dbContext = new ModelContext();
IEnumerable<IEnumerable<Town>> towns = dbContext.Towns.OrderBy(t => t.TownID).Batch(200000);
foreach (var batch in towns)
{
SearchClient.Instance.IndexMany(batch, SearchClient.Instance.Settings.DefaultIndex, "Town", new SimpleBulkParameters() { Refresh = false });
}
注意:批处理方法来自此项目:https://code.google.com/p/morelinq/
搜索客户端是这样的:https://github.com/Mpdreamz/NEST
获取"不允许新事务,因为会话中正在运行其他线程".
它与foreach循环或任何人通常与此消息一起出现问题无关.
我在整个请求中使用带有repositoy模式和公共上下文的EF4.有些事情发生了,无法准确确定是什么,只要我尝试使用上下文保存变更,跨请求,我就会收到此消息,并且只有在我回收应用程序池后才会消失.
我关闭连接了吗？我该怎么说？我是否为每个请求使用了新的上下文？是.
这是怎么回事？有解决方法吗？
编辑:(上下文工厂)
private static Dictionary<string, CoinEntities> _instances;
public static CoinEntities DefaultInstance
{
get
{
if (HttpContext.Current == null)
{ //todo: mock instead. testing.
if (!Instances.ContainsKey("_TEST"))
Instances["_TEST"] = new CoinEntities();
return Instances["_TEST"];
}
if (!Instances.ContainsKey("_DEFAULT"))
Instances["_DEFAULT"] = new CoinEntities();
return Instances["_DEFAULT"];
}
}
使用实体框架4.3.1数据库首先,经常提交/保存对象更改到数据库的好方法是什么？在下面,我想在quickbooks电话之后立即保存发票,而不是等待发布所有发票的风险.但是,我不能每次在循环中调用SaveChanges,它会抛出异常.
在每个对象上使用.Save()方法会很方便,也许有一个很好的方法可以做到这一点？
var unpostedInvoices = entities.GetUnpostedInvoices();
foreach (Invoice invoice in unpostedInvoices)
{
// this takes a long time
var invoiceDto = quickbooks.PostInvoice(invoice);
invoice.Posted = true;
invoice.TransactionId = invoiceDto.TransactionId;
// I'd like to save here rather than after the foreach loop, but this will fail
//entities.SaveChanges();
}
// this works, but I don't want to risk waiting this long to save
entities.SaveChanges();
这是在循环中调用SaveChanges()时抛出的异常.
New transaction is not allowed because there are other threads running in the session.
at System.Data.SqlClient.SqlConnection.OnError(SqlException exception, Boolean …