我在Stack Exchange的Code Review（测试版）上发布了此代码段，以便获得有关如何最好地重构多部分LINQ查询的反馈。
对LINQ相对较新，我不确定从哪个查询开始。
如果有人能给我任何关于在方法中组合一些LINQ查询的建议，我会很感激;特别是 '排除' IQueryable集合到主查询中（参见注释）。
此时查询的性能不是特别高，为了从代码角度提高性能，您可以提出任何建议。
收到的关于Code Review的评论更具体系结构，但我目前无法在此时向数据库移动任何内容。
我很欣赏这是一个很大的方法，但我已经发布了很多内容来提供上下文。
提前感谢您提出的任何建议。
/// Get templates by username and company
public List<BrowsingSessionItemModel> GetItemBrowsingSessionItems(
int companyId,
string userName,
Boolean hidePendingDeletions,
Boolean hideWithAppointmentsPending,
Boolean hideWithCallBacksPending,
int viewMode,
string searchString,
List<int?> requiredStatuses,
List<int?> requiredSources,
string OrderBy,
BrowsingSessionLeadCustomField fieldFilter)
{
try
{
IQueryable<Lead> exclude1;
IQueryable<Lead> exclude2;
IQueryable<Lead> exclude3;
//To prepare call backs pending
if (hideWithCallBacksPending == true)
{
exclude1 = (from l1 in db.Leads
where (l1.Company_ID == companyId)
from l2 // Hiding Pending Call Backs
in db.Tasks
.Where(o => (o.IsCompleted ?? false == false)
&& (o.TaskType_ID == (int)RecordEnums.TaskType.PhoneCall)
&& (o.Type_ID == (int)RecordEnums.RecordType.Lead)
&& (o.Item_ID == l1.Lead_ID)
&& (o.Due_Date > EntityFunctions.AddDays(DateTime.Now, -1))
)
select l1);
}
else
{
exclude1 = (from l1 in db.Leads
where (0 == 1)
select l1);
}
//To prepare appointments backs pending
if (hideWithAppointmentsPending == true)
{
exclude2 = (from a1 in db.Leads
where (a1.Company_ID == companyId)
from a2 // Hiding Pending Appointments
in db.Tasks
.Where(o => (o.IsCompleted ?? false == false)
&& (o.TaskType_ID == (int)RecordEnums.TaskType.Appointment)
&& (o.Type_ID == (int)RecordEnums.RecordType.Lead)
&& (o.Item_ID == a1.Lead_ID)
&& (o.Due_Date > EntityFunctions.AddDays(DateTime.Now, -1))
)
select a1);
}
else
{
exclude2 = (from a1 in db.Leads
where (0 == 1)
select a1);
}
//To prepare deletions
if (hidePendingDeletions == true)
{
exclude3 = (from d1 in db.Leads
where (d1.Company_ID == companyId)
from d2 // Hiding Pending Deletions
in db.LeadDeletions
.Where(o => (o.LeadId == d1.Lead_ID))
select d1);
}
else
{
exclude3 = (from d1 in db.Leads
where (0 == 1)
select d1);
}
// MAIN QUERY <--
IQueryable<Lead> list = (from t1 in db.Leads
from t2
in db.LeadSubOwners
.Where(o => t1.Lead_ID == o.LeadId && o.Expiry >= DateTime.Now)
.DefaultIfEmpty()
where (t1.Company_ID == companyId)
where ((t2.Username == userName) && (viewMode == 1)) || ((t1.Owner == userName) && (viewMode == 1)) || ((viewMode == 2)) // Either owned by the user or mode 2 (view all)
select t1).Except(exclude1).Except(exclude2).Except(exclude3);
// Filter sources and statuses seperately
if (requiredStatuses.Count > 0)
{
list = (from t1 in list
where (requiredStatuses.Contains(t1.LeadStatus_ID))
select t1);
}
if (requiredSources.Count > 0)
{
list = (from t1 in list
where (requiredSources.Contains(t1.LeadSource_ID))
select t1);
}
// Do custom field filter here
if (fieldFilter != null)
{
string stringIntegerValue = Convert.ToString(fieldFilter.IntegerValue);
switch (fieldFilter.FieldTypeId)
{
case 1:
list = (from t1 in list
from t2
in db.CompanyLeadCustomFieldValues
.Where(o => t1.Lead_ID == o.Lead_ID && fieldFilter.TextValue == o.LeadCustomFieldValue_Value)
select t1);
break;
case 2:
list = (from t1 in list
from t2
in db.CompanyLeadCustomFieldValues
.Where(o => t1.Lead_ID == o.Lead_ID && stringIntegerValue == o.LeadCustomFieldValue_Value)
select t1);
break;
default:
break;
}
}
List<Lead> itemsSorted; // Sort here
if (!String.IsNullOrEmpty(OrderBy))
{
itemsSorted = list.OrderBy(OrderBy).ToList();
}
else
{
itemsSorted = list.ToList();
}
var items = itemsSorted.Select((x, index) => new BrowsingSessionItemModel
{
Id = x.Lead_ID,
Index = index + 1
});
return items.ToList();
}
catch (Exception ex)
{
logger.Info(ex.Message.ToString());
return new List<BrowsingSessionItemModel>();
}
}
答案 0 :(得分：2)
我不明白为什么会这样：
false == false
那：
where (0 == 1)
然后排除1和2：
//To prepare call backs pending
var phoneCallTypeId = (int) RecordEnums.TaskType.PhoneCall;
var exclude1 = GetExclude(hideWithCallBacksPending, companyId, phoneCallTypeId);
//To prepare appointments backs pending
var appointmentTypeId = (int) RecordEnums.TaskType.Appointment;
var exclude2 = GetExclude(hideWithCallBacksPending, companyId, appointmentTypeId);
使用以下GetExclude方法：
private object GetExclude(bool hideWithCallBacksPending, int companyId, int typeId)
{
return hideWithCallBacksPending
? (from l1 in db.Leads
where (l1.Company_ID == companyId)
from l2
// Hiding Pending Call Backs
in
db.Tasks.Where(
o =>
(o.IsCompleted ?? false) &&
(o.TaskType_ID == typeId) &&
(o.Type_ID == (int) RecordEnums.RecordType.Lead) &&
(o.Item_ID == l1.Lead_ID) &&
(o.Due_Date > EntityFunctions.AddDays(DateTime.Now, -1)))
select l1)
: (from l1 in db.Leads where (0 == 1) select l1);
}
Exclude3：
//To prepare deletions
var exclude3 = hidePendingDeletions
? (from d1 in db.Leads
where (d1.Company_ID == companyId)
from d2
// Hiding Pending Deletions
in db.LeadDeletions.Where(o => (o.LeadId == d1.Lead_ID))
select d1)
: (from d1 in db.Leads where (0 == 1) select d1);
排除1和2可以内联调用，因为它们很短：
// Either owned by the user or mode 2 (view all)
...select t1)
.Except(GetExclude(hideWithCallBacksPending, companyId, phoneCallTypeId))
.Except(GetExclude(hideWithCallBacksPending, companyId, appointmentTypeId))
.Except(exclude3);