var query = from c in context.Albums
where c.AlbumID in albumIds
select c.Albumname;
Here albumIds is IENUM<> of some custom type(in my case its an Entity)
When I do the above query I get an error
Operator == cannot be applied to type int and IEnumerable
This error is acceptable but how do I overcome this
Turn it around slightly - you want to check whether your enumerable of album ids contains the id of an album you have just iterated to in your linq. So something like this ...
albumIds = {1,2,13,25,277,567};
var query = context.Albums.Where(x=> albumIds.Contains(x.ID));
(Sorry, writing example code without a tool in front of me so forgive any obvious mistakes. Hopefully you can get the idea from this though).
var albumIds= new string[] { "900", "801", "802", "803","906" };
var lstData = context.tbl.Where(
x => (x.TimeCreated >= yesterday && x.TimeCreated < today) &&
albumIds.Contains(x.TransactionSetId)
).Select(x => x.X12_Interchange).ToList();
Related
I completely understand that this is because LINQ query requires the whole expression to be translated to a server , and therefore I cant call an outside method in it. but as I have looked at other answers there is not relative solution to this. the only approach that I thought about is to loop through all the items in the model and than passing them to the query one by one but even though this approach would not help so I am seeking help in here for anyone to help me to figure out how to call a method or a way of calling a method appendstr that initializes a.PostedDate before checking its actual equivalent value in the giving LINQ Query.
[HttpGet]
public ActionResult SearchResult(int? page, string searchTitle = null, string searchLocation = null, string last24 = "")
{
ViewBag.searchTitle = searchTitle;
ViewBag.searchLocation = searchLocation;
ViewBag.page = page;
ViewBag.last24 = last24;
setUpApi(searchTitle, searchLocation);
var result = new List<AllJobModel>().AsQueryable();
if (!string.IsNullOrEmpty(ViewBag.searchTitle) || !string.IsNullOrEmpty(ViewBag.searchTitle) || !string.IsNullOrEmpty(ViewBag.last24))
{
setUpApi(searchTitle, searchLocation);
DateTime now = DateTime.Now;
result = db.AllJobModel.Where(a => a.JobTitle.Contains(searchTitle) && a.locationName.Contains(searchLocation) &&
appendstr(a.PostedDate).Equals(now.AddHours(-24).ToString("MM-dd-yyyy")));
}
else
{
result = from app in db.AllJobModel select app;
}
return View(result.ToList().ToPagedList(page ?? 1, 5));
}
The second method that gets called in the LINQ Query
public string appendstr(string str)
{
var x = str.Split(' ');
return 01 + "-" + x[1] + "-" + x[2];
}
I think you already understand that the .NET code you write in the Where clause is actually an expression that is parsed and converted to SQL. So if you have a funky string manipulation method, you can't use it directly.
The brute force option, as you seem to already understand, it to materialize the query first and then run the C# code over the results. You can do this with ToList() or AsEnumerable().
result = db.AllJobModel
.Where
(
a => a.JobTitle.Contains(searchTitle)
&& a.LocationName.Contains(searchLocation)
)
.AsEnumerable()
.Where
(
a => appendstr(a.PostedDate).Equals(now.AddHours(-24).ToString("MM-dd-yyyy")))
);
However in your specific case you can try a trick. You are attempting a date comparison, which SQL is perfectly capable of doing... you just need to convert that funky PostedDate to a SQL DateTime so that you can compare it directly. The gimmick for that is to use SqlFunctions.DateAdd to add null interval (e.g. 0 days). This implicitly converts the string to DateTime, where you can now query on the SQL side:
var targetDate = DateTime.Now.AddHours(-24);
result = db.AllJobModel
.Where
(
a => a.JobTitle.Contains(searchTitle)
&& a.LocationName.Contains(searchLocation)
&& SqlFunctions.DateAdd("DAY", 0, a.PostedDate) == targetDate
);
Credit goes to this post for the workaround.
I have, what I thought was a pretty straight-forward query.
In normal Sql this would read:
SELECT [column names]
FROM agentscheduledetail
WHERE (date = '2012-07-04') AND
(
exception = 'Break (No Sign Off)' OR
exception = 'Break' OR
exception = 'Break (Signed Out)'
)
This returns approx 900 records.
However, when I try to enter this into my controller, I end up with around 300,000 records - so I think my AND and ORs are not working. I've tried Linqer, but can't get it to work (I'm aware this may not be actual LINQ but the equivalent query in VS - if there is a linq version... I'd be grateful for that too if possible).
My controller query is:
var dte = DateTime.Today;
return View(db.agentscheduledetails.Where
(
d => d.date == dte && d.agentName.StartsWith("ta") &&
(
d.exception == "Break (No Sign Off)" ||
d.exception == "Break" ||
d.exception == "Break (Signed Out)"
)
).ToList()
);
Can anyone either a) let me know where I'm going wrong with my && || (and/or), or b) is there a way of stepping through the code in VS, to see what the above query translates to in normal SQL so I can try to figure out where I'm going wrong?
Thanks for any help,
Mark
The following is perhaps a simplified version of what you are trying to do, also your LINQ contains an additional statement compared to the SQL where it is comparing the agent name?
var currentDate = DateTime.Today;
var exceptionTypes = new List<string>() { "Break (No Sign Off)",
"Break", "Break (Signed Out)" };
db.agentscheduledetails.Where(d => d.date == currentDate &&
exceptionTypes.Contains(d.exception));
One thing that you could try is getting hold of a copy of LinqPad, this will let you run your LINQ statement against a database and will show you what the generated SQL statement is.
Aside from anything else,
d.agentName.StartsWith("ta")
does not appear in your original sql...?
hi guys i am stuck converting below sql to LINQ query.
all i want is to have maximum number from list of (FA-00001 ,FA-00059)
SELECT MAX(CAST(SUBSTRING(ReferenceId, PATINDEX('%-%', ReferenceId) + 1, LEN(ReferenceId) - PATINDEX('%-%', ReferenceId)) AS int)) AS MaxReferenceId FROM [ClientRC].[dbo].[EHO_Action]
is this possible to convert to LINQ? thanks
An alternative approach using anonymous projection:
var y = (from record in
(from record in db.ClientRC
select new
{
Group = "x",
ReferenceNumber = Convert.ToInt32(record.ReferenceId.Split('-')[1])
})
group record by new { record.Group } into g
select new
{
MaxReferenceId = g.Max(p => p.ReferenceNumber)
});
http://msdn.microsoft.com/en-us/library/bb386972.aspx
var myvar = (from v in db.object where v!=null select v.id).Max();
MSDN has lots of examples for stuff like this.
Or, you can execute queries directly against a datacontext if you're using entity framework. Just make sure if you're doing anything with parameters you're parameterizing the query and not taking user input directly into it.
http://msdn.microsoft.com/en-us/library/ee358769.aspx
Try this..
var list = DBContext.EHO_Action
.Where(x => x.YourListColumn != null)
.Select(x => x.YourListColumn).ToList(); // Take the list (FA-00001 ,FA-00059) from db to a list
var maxNo = list.Max(x => Convert.ToInt32(x.Split('-')[1]));
Please change the context and column names according to your Linq context.
If you want to use sql you can do it this way..
var list = DBContext.ExecuteQuery<string>("select yourreqrdcolumn from [ClientRC].[dbo].[EHO_Action]");
I have a label to show BookName. I get it from table which name tblBooks. I don't know how to show Book Name into the label.
var query = from b in dc.tblBooks.Where(b=>b.BookID == 'B01') select b;
Can you help me know.
Your query as written will return a collection of books—IQueryable<Book>. If you're sure there will only be one result in this query, you can call SingleOrDefault, which will execute the query immediately and give you the actual book.
var Book = dc.tblBooks.Where(b => b.BookID == 'B01').SingleOrDefault();
if (Book != null)
myLabel.Text = Book.BookName;
Or you can simply say:
var Book = dc.tblBooks.SingleOrDefault(b => b.BookID == 'B01');
Which does the same thing.
If you're 110% sure there will always be a result, and you don't want to check for null, then you can use Single, which will do the same thing, except throw an exception if no results are found, where SingleOrDefault simple returns null.
var Book = dc.tblBooks.Single(b=>b.BookID == 'B01');
myLabel.Text = Book.BookName;
Try:
label.Text = query.FirstOrDefault().BookName;
var depts = ctx.Departments
.OrderBy(d => d.deptName)
.Select(d => d.deptNo);
foreach (int deptNumber in depts) {
var deptReports = from d in ctx.Departments
join r in matchingIncidents on d.deptNo equals r.deptNo
where r.deptNo == deptNumber
select r;
int deptReportsCount = deptReports.Count();
I am completely baffled! All the questions about this error say to use == on primitive fields (such as IDs), which I'm doing. Anything I do to this query generates the exception. The exact same code worked before and I don't know what I've done to it! Could someone please explain to me what's going on?
Also, I remember there being an EntityFramework class with methods that allowed you to convert objects within a query (e.g. dates), does anyone know what this class is?
UPDATE:
Here are the changes I made (it now works).
var deptReports = from r in matchingIncidents
join d in ctx.Departments on r.deptNo equals d.deptNo
where r.deptNo == deptNumber
select r;
matchingIncidents looks like a local collection of a complex type (because you are using r.deptNo). That's not allowed in LINQ to Entities. You could try this instead:
foreach (int deptNumber in depts) {
var deptReports = from d in ctx.Departments
join r in matchingIncidents.Select(m => m.deptNo)
on d.deptNo equals r
where r == deptNumber
select r;
int deptReportsCount = deptReports.Count();
matchingIncidents.Select(m => m.deptNo) is now a local collection of primitive types and deptReports is a sequence of int (assuming that deptNo is of type int). But for counting the resulting elements it should be still fine.
Edit
And you are probably searching for the static EntityFunctions class:
http://msdn.microsoft.com/en-us/library/system.data.objects.entityfunctions.aspx
Could the issue be:
join r in matchingIncidents on d.deptNo == r.deptNo