I have the following linq query that is throwing an error if a budget doesn't have any categories. Am I doing something wrong? Can I just set sum to return 0 if there are no categories? I'm fairly new to linq to sql.
var r = from rec in DbContext.budgets
where rec.budgetID == updatedBudget.budgetID
select new
{
rec.budgetID,
rec.totalIncome,
totalSpent = rec.categories.Sum(a => a.amount)
};
return new JsonResult(r.FirstOrDefault(), JsonSettings);
you can try this.
var r = from rec in DbContext.budgets
where rec.budgetID == updatedBudget.budgetID
select new
{
rec.budgetID,
rec.totalIncome,
totalSpent = rec.categories != null ? rec.categories.Sum(a => a.amount) : 0
};
return new JsonResult(r.FirstOrDefault(), JsonSettings);
Related
How would I go about changing my if statement and foreach to something cleaner in linq using select and where.
I've tried to make the if statement into a where clause and then use the select query as a replacement for the Foreach loop but that seem to have type issues and wasn't working.
{
StripeConfiguration.ApiKey = _appSettings.StripeSecretKey;
var profile = await _userManager.FindByIdAsync(customerServiceID);
var stripeId = profile.StripeAccountId;
if (stripeId == null)
throw new ArgumentException("No associated Stripe account found.");
List<PaymentMethodDto> result = new List<PaymentMethodDto>();
var options = new PaymentMethodListOptions
{
Customer = stripeId,
Type = "card",
};
var service = new PaymentMethodService();
var payments = await service.ListAsync(options);
if (payments != null && payments.Data?.Count > 0)
{
payments.Data.ForEach((x) =>
{
result.Add(
new PaymentMethodDto
{
Brand = x.Card.Brand,
LastDigits = x.Card.Last4,
StripeToken = x.Id,
CustomerID = x.CustomerId
});
});
}
return result;
}
Just do a regular Select.
List<PaymentMethodDto> result = payments.Data.Select(x => new PaymentMethodDto
{
Brand = x.Card.Brand,
LastDigits = x.Card.Last4,
StripeToken = x.Id,
CustomerID = x.CustomerId
})
.ToList();
If payments.Data has nothing in it, this will give you an empty list, which is what you want.
If payments is null, you'll get an exception, which I think if you think about it really hard is probably what you really want in that case too. Why would .ListAsync() yield a null value?
I have a linq query which joins a couple of tables and returns the value into an object. The query was working fine, till i added a where clause to in. Aftre the where clause, my query returns null.
Here's the code:
List<Int32> resourceSupervisorIdList = new List<Int32>();
resourceSupervisorIdList.Add(searchCriteriaTimesheet.ResourceId);
foreach (resource res in allSubordinateResources)
{
if (!resourceSupervisorIdList.Contains(res.id_resource))
resourceSupervisorIdList.Add(res.id_resource);
}
using (tapEntities te = new tapEntities())
{
var timesheetAll = (from tsh in te.timesheet_header
join rs in te.resources on tsh.id_resource equals rs.id_resource
join tsd in te.timesheet_detail on tsh.id_timesheet equals tsd.id_timesheet
where (resourceSupervisorIdList.Contains(rs.id_resource_supervisor))
select new TimesheetHeaderDetailsItem()
{
OrganizationId = rs.id_organization,
ProjectId = tsd.id_project,
StartDate = tsh.dte_period_start,
EndDate = tsh.dte_period_end,
ApprovedDate = tsh.dte_approved,
RejectedDate = tsh.dte_rejected,
SubmittedDate = tsh.dte_submitted,
});
if (timesheetAll == null || timesheetAll.Count() == 0)
{
return result;
}
}
Now, after adding the where clause, the code runs into the if condition. There are matching records in the table, but still i'm not able to get any records.
rs.id_resource_supervisor
is of type int in the mysql db.
I'm trying to implement a T-SQL equivalent of a where in (select ...) code in LINQ.
This is what I have now:
int contactID = GetContactID();
IEnumerable<string> threadList = (from s in pdc.Messages
where s.ContactID == contactID
group 1 by new { s.ThreadID } into d
select new { ThreadID = d.Key.ThreadID}).ToList<string>();
var result = from s in pdc.Messages
where threadList.Contains(s.ThreadID)
group new { s } by new { s.ThreadID } into d
let maxMsgID = d.Where(x => x.s.ContactID != contactID).Max(x => x.s.MessageID)
select new {
LastMessage = d.Where(x => x.s.MessageID == maxMsgID).SingleOrDefault().s
};
However, my code won't compile due to this error for the ToList():
cannot convert from
'System.Linq.IQueryable<AnonymousType#1>'
to
'System.Collections.Generic.IEnumerable<string>'
Anyone have any suggestions on how to implement this? Or any suggestions on how to simplify this code?
Your query returns a set of anonymous types; you cannot implicitly convert it to a List<string>.
Instead, you should select the string itself. You don't need any anonymous types.
Change it to
var threadList = pdc.Messages.Where(s => s.ContactID == contactID)
.Select(s => s.ThreadID)
.Distinct()
.ToList();
var result = from s in pdc.Messages
where threadList.Contains(s.ThreadID)
group s by s.ThreadID into d
let maxMsgID = d.Where(x => x.ContactID != contactID).Max(x => x.MessageID)
select new {
LastMessage = d.Where(x => x.MessageID == maxMsgID).SingleOrDefault()
};
I'm using L2S for database operations in my asp.net mvc application I have following simple query in my repository
(from pt in db.oaProjectTasks
where pt.ProjectID == ProjectID
join t in db.oaTasks on pt.TaskID equals t.TaskID
where t.ParentTaskID == null
let daypassed = GetDaysPassed(t.StartDate,t.Duration)
select new ChartTask{TaskNumber = t.TaskNumber,StartDate = t.StartDate,
DurationRemaining = t.Duration - daypassed,TaskDescription = t.Task, DaysPassed = daypassed,Duration = t.Duration }).ToList();
below is the defination of GetDayPassed method
private int GetDaysPassed(DateTime StartDate, int Duration)
{
int retVal;
if ((DateTime.Now - StartDate).Days > 0)
{
if ((DateTime.Now - StartDate.AddDays(Duration)).Days > 0)
{
retVal = Duration;
}
else
{
retVal = (DateTime.Now - StartDate).Days;
}
}
else
{
retVal = 0;
}
return retVal;
}
there is no compile time error, however, when i execute the code it gives me invalidOperationException with following message.
Could not translate expression 'Table(oaProjectTask).Where(pt => (pt.ProjectID == Invoke(value(System.Func`1[System.Int64])))).Join(Table(oaTask), pt => pt.TaskID, t => t.TaskID, (pt, t) => new <>f__AnonymousType5f`2(pt = pt, t = t)).Where(<>h__TransparentIdentifier2 => (<>h__TransparentIdentifier2.t.ParentTaskID == null)).Select(<>h__TransparentIdentifier2 => new
how can I get around this? if calling a method in query is not allowed how can I make a simple calculation in Linq query instead of calling GetDayPassed method?
You can try this:
(from pt in db.oaProjectTasks
where pt.ProjectID == ProjectID
join t in db.oaTasks on pt.TaskID equals t.TaskID
where t.ParentTaskID == null
select t)
.ToList() // T-SQL query will be executed here and result will be returned
.Select(t => new ChartTask {
TaskNumber = t.TaskNumber,
StartDate = t.StartDate,
DurationRemaining = t.Duration - GetDaysPassed(t.StartDate,t.Duration),
TaskDescription = t.Task,
DaysPassed = GetDaysPassed(t.StartDate,t.Duration),
Duration = t.Duration });
The problem is that Linq to Sql tries to translate your custom function to T-SQL and since it doesn't know how to do that it will throw the exception. In my case Linq will construct the query, execute it (after the call to .ToList()) and your function will be called as Linq to objects query.
How can I update a record against specific id in LINQ to SQL?
LINQ is a query tool (Q = Query) - so there is no magic LINQ way to update just the single row, except through the (object-oriented) data-context (in the case of LINQ-to-SQL). To update data, you need to fetch it out, update the record, and submit the changes:
using(var ctx = new FooContext()) {
var obj = ctx.Bars.Single(x=>x.Id == id);
obj.SomeProp = 123;
ctx.SubmitChanges();
}
Or write an SP that does the same in TSQL, and expose the SP through the data-context:
using(var ctx = new FooContext()) {
ctx.UpdateBar(id, 123);
}
In the absence of more detailed info:
using(var dbContext = new dbDataContext())
{
var data = dbContext.SomeTable.SingleOrDefault(row => row.id == requiredId);
if(data != null)
{
data.SomeField = newValue;
}
dbContext.SubmitChanges();
}
AdventureWorksDataContext db = new AdventureWorksDataContext();
db.Log = Console.Out;
// Get hte first customer record
Customer c = from cust in db.Customers select cust where id = 5;
Console.WriteLine(c.CustomerType);
c.CustomerType = 'I';
db.SubmitChanges(); // Save the changes away
DataClassesDataContext dc = new DataClassesDataContext();
FamilyDetail fd = dc.FamilyDetails.Single(p => p.UserId == 1);
fd.FatherName=txtFatherName.Text;
fd.FatherMobile=txtMobile.Text;
fd.FatherOccupation=txtFatherOccu.Text;
fd.MotherName=txtMotherName.Text;
fd.MotherOccupation=txtMotherOccu.Text;
fd.Phone=txtPhoneNo.Text;
fd.Address=txtAddress.Text;
fd.GuardianName=txtGardianName.Text;
dc.SubmitChanges();
I found a workaround a week ago. You can use direct commands with "ExecuteCommand":
MDataContext dc = new MDataContext();
var flag = (from f in dc.Flags
where f.Code == Code
select f).First();
_refresh = Convert.ToBoolean(flagRefresh.Value);
if (_refresh)
{
dc.ExecuteCommand("update Flags set value = 0 where code = {0}", Code);
}
In the ExecuteCommand statement, you can send the query directly, with the value for the specific record you want to update.
value = 0 --> 0 is the new value for the record;
code = {0} --> is the field where you will send the filter value;
Code --> is the new value for the field;
I hope this reference helps.