I have MySQL query
SELECT Task_Number, BM_Number, BU, Status
FROM
eng_effort
INNER JOIN eng_task on eng_effort.Eng_Task_ID = eng_task.Eng_Task_ID
where Status = "In Progress" and User_ID = "7"
group by Task_Number;
How do i write it in linq. please help.
Using the LINQ syntax, you can write something like this:
var query = (from effort in context.eng_effort
join task in context.eng_task on effort.Eng_Task_ID equals task.Eng_Task_ID
where task.Status == "In Progress" && task.User_ID == "7"
select new { task.Task_Number, ... })
.GroupBy(a => a.Task_Number);
Also, are you sure User_ID is a text column?
With the extension method syntax:
context.eng_effort
.Join(
context.eng_task,
effort => effort.Eng_Task_ID,
task => task.Eng_Task_ID,
(effort, task) => (effort, task)) // Using a ValueTuple here
.Where(et => et.task.Status == "In Progress" && et.task.User_ID == "7")
.Select(et => new { et.task.Task_Number, ... })
.GroupBy(a => a.Task_Number);
Or you could perform a Perform grouped join.
Related
var loggedInHours = db.LoginLogs.Where(l => l.UserId == u.Id && l.UserSessionStop != null)
.Sum(ls=> ls.UserSessionStart.Subtract(ls.UserSessionStop.Value).Hours)
I am trying to calculate Total LoggedIn Hours using this linq query..
But its giving me this error
"Only one expression can be specified in the select list when the subquery is not introduced with EXISTS."
I don't know whats wrong with it..plz help
Try if this works:
var loggedInHours = db.LoginLogs.Where(l => l.UserId == u.Id && l.UserSessionStop != null)
.Select(l=> new {
StartTime = l.UserSessionStart,
EndTime = l.UserSessionStop
})
.ToList()
.Sum(c=> c.StartTime - c.EndTime);
btw, Is UserSessionStop nullable? If yes, then what will be the value to be subtracted?
I would like to create a single query that "adjusts" it's where clause based on a tuple. The first item in the tuple contains a enum value indicating the field in which to filter. The second tuple item is the filter value.
Notice the query below does not work:
var query = from p in db.Categories
where ( QueryBy.Item1 == CategoryFields.Name && p.Name == (string)(QueryBy.Item2) ) ||
( QueryBy.Item1 == CategoryFields.Id && p.Id == (long)(QueryBy.Item2) ) ||
( QueryBy.Item1 == CategoryFields.Description && p.Description == (string)(QueryBy.Item2) ) ||
( QueryBy.Item1 == CategoryFields.SortOrder && p.SortOrder == (int)(QueryBy.Item2) )
select...
if (query.Count() == 1) // ERRORS HERE CONVERSION OF INT
A similar query with only this where clause change will works:
var query = from p in db.Categories
where ( QueryBy.Item1 == CategoryFields.Name && p.Name == (string)(QueryBy.Item2) )
select...
if (query.Count() == 1) // Works HERE
Any idea what could be wrong? Can it be that LINQ where clause perform a short-circuit evaluation and thus the cast of item2 fails? Is there a better way to accomplish my overall goal of adjusting where clause?
Thanks in advance for your help!
LINQ to SQL isn't smart enough to optimize your query and generate it dynamically based on the value of your QueryBy.Item1. It will simply generate a SQL query let SQL server decide this for itself.
When you know that, the error makes sense, since it's impossible for one single value to be castable to both int, long, and string.
In your case you would be better of dynamically generating the right where clause. You can do this with the PredicateBuilder:
IQueryable<Category> query = db.Categories;
var whereClause = PredicateBuilder.False<Category>();
switch (QueryBy.Item1)
{
case CategoryFields.Name:
long id = (string)QueryBy.Item2;
whereClause = whereClause.Or(p => p.Name == name);
break;
case CategoryFields.Id:
string name = (string)QueryBy.Item2;
whereClause = whereClause.Or(p => p.Id == id);
break;
case CategoryFields.Description:
string des = (string)QueryBy.Item2;
whereClause =
whereClause.Or(p => p.Description == des);
break;
case CategoryFields.Id:
string sort = (int)QueryBy.Item2;
whereClause =
whereClause.Or(p => p.SortOrder == sort);
break;
}
query = query.Where(whereClause);
I have this:
var q = (from order in db.Orders
from payment in db.Payments
.Where(x => x.ID == order.paymentID)
.DefaultIfEmpty()
from siteUser in db.SiteUsers
.Where(x => x.siteUserID == order.siteUserID)
.DefaultIfEmpty()
where siteUser.siteUserID != null
select new
{
order.orderID,
order.dateCreated,
payment.totalAmount,
siteUser.firstName,
siteUser.lastName
});
I want to add on to it like this:
switch (_qs["sort"])
{
case "0":
q = q.OrderByDescending(x => x.dateCreated);
break;
case "1":
q = q.OrderBy(x => x.dateCreated);
break; ...
I've done this before with a single table, but the multiple tables in the first code block force me to specify a select statement which causes it to be an anonymous type. How can this be done?
Note: I even tried to make a class with the properties that i'm selecting and casting the query to this type, still a no go.
Not sure I understand the question but the code you pasted looks valid to me.
I checked:
var q = (
from order in db.Orders
join payment in db.Payments on
order.paymentID equals payment.ID into payments
from payment in payments.DefaultIfEmpty()
join siteUser in db.SiteUsers on
order.siteUserID equals siteUser.siteUserID into siteUsers
from siteUser in siteUsers.DefaultIfEmpty()
where siteUser.siteUserID != null
select
new
{
order.orderID,
order.dateCreated,
payment.totalAmount,
siteUser.firstName,
siteUser.lastName
});
switch (sort)
{
case "0":
q = q.OrderByDescending(x => x.dateCreated);
break;
case "1":
q = q.OrderBy(x => x.dateCreated);
break;
}
var restult = q.ToList();
This works.
I am really new to Linq and am using Linq-to-Sql as follows. However in the following example, my where clause never gets executed and the resultant query attempts to fetch all the records from my table, ignoring even the take method.
Can somebody point out as to what i am doing wrong
var baseQry = db.Table;
baseQry.Where(a => a.tab_id == theId);
baseQry.Select(o => new
{
o.name,
o.display_name,
o.type,
o.info,
time_stamp = (Convert.ToDateTime(o.timestamp).ToLongDateString())
}).Take(10);
baseQry.ToList();
Your second line...
baseQry.Where(a => a.tab_id == theId);
...is essentially a no-op, because the resulting query isn't carried over into your .Select clause.
You need to change it to this:
var baseQry = db.Table;
var results = baseQry
.Where(a => a.tab_id == theId)
.Select(o => new
{
o.name,
o.display_name,
o.type,
o.info,
time_stamp = (Convert.ToDateTime(o.timestamp).ToLongDateString())
})
.Take(10)
.ToList();
Just began to develop using LINQ, and still can't understand some simple things.
So,
LinqTable.SingleOrDefault(t=>(t.Field1=="value1")) is equal to SQL "SELECT * FROM LinqTable WHERE Field1="value1" LIMIT 1"
How to create (using Linq) the query like "SELECT * FROM LinqTable WHERE Field1="value1" AND Field2="value2" LIMIT 1?
SingleOrDefault(t=>(t.Field1=="value1" && t.Field2=="value2"))
LinqTable.Where(row => row.Field1 == "value1" && row.Field2 == "value2").FirstOrDefault();
Normally, you'd want to use Where to do this:
var result = LinqTable.Where(t => t.Field1 == "value1" && t.Field2 == "value2").SingleOrDefault();
You can do this directly in the SingleOrDefault line as well:
var result = LinqTable.SingleOrDefault(t => t.Field1 == "value1" && t.Field2 == "value2");