I have the following where I need to get only the Date (not datetime) from
ReqDate and RepDeclined which are both nullable datetime fields.
var info = from pr in db.Prog
join tf in db.In_Lens
on pr.PID equals tf.PID
select new
{ ReqDate = String.Format("{0:MM/dd/yyyy}",tf.ReqDate),
ReqDeclinedDate = tf.ReqDeclined.ToString("MM/dd/yyyy")
}).ToList()
It is not working as ReqDate and RepDeclined are both nullable datetime fields.
I also tried String.Format but no luck.
It says no overload for method.
You can try this, more elegant i think
var info = from pr in db.Prog
join tf in db.In_Lens
on pr.PID equals tf.PID
select new
{ ReqDate = !string.IsNullOrEmpty(tf.ReqDate) ? string.Format("{0:MM/dd/yyyy}",tf.ReqDate) : string.Empty(),
ReqDeclinedDate = !string.IsNullOrEmpty(tf.ReqDeclined) ? tf.ReqDeclined.ToString("MM/dd/yyyy") : string.Empty()
}).ToList()
I just way changed my answer.. basically.. you need to get back a couple datetimes in your new collection.. and then when you use those values, you can do the String.Format(). The reason is LINQ boils down to SQL, and there's no String.Format() converter (yet?).
so when you loop through the results, you can transform those results to display propertly (i.e. String.Format(...)).. but you will not be able to select out and convert the results in one linq statement, you might be able to do it LAMBDA (.ForEach()), which would be able to iterate through the results, however, it would just be a shorhtand way of doing what i described above..
...to the best of my knowledge
Related
i have got a big problem with converting dates in c#,i want to query using LINQ,in my condition i have to put date,if i put DateTime its in american format and database which expecting UK format does not recognize the date,if use ToString('dd,MM,yyyy') to get british format,i cant use string in LINQ condition,what should i do?
var rslt=(from t in cr.table1
join v in cr.errorCatGroup
on t.m_error_id equals v.m_error_id
where t.m_date >= myDateTime1 && t.m_date <= myDateTime2
select new {
GroupName=t.Error
}).ToList();
i get mDateTime1 and myDateTime2 like :
CultureInfo ukCulture = new CultureInfo("en-GB");
DateTime myDateTime1 = DateTime.Parse("30/09/2018", ukCulture.DateTimeFormat);
DateTime result12 = DateTime.ParseExact("01-10-2018", "d-M-yyyy", CultureInfo.CurrentCulture);
so whats the right way of using it in LINQ
I have some errors using Linq on DataTable and I couldn't figure it out how to solve it. I have to admit that i am pretty new to Linq and I searched the forum and Internet and couldn't figure it out. hope you can help.
I have a DataTable called campaign with three columns: ID (int), Product (string), Channel (string). The DataTable is already filled with data. I am trying to select a subset of the campaign records which satisfied the conditions selected by the end user. For example, the user want to list only if the Product is either 'EWH' or 'HEC'. The selection criteria is dynaically determined by the end user.
I have the following C# code:
private void btnClick()
{
IEnumerable<DataRow> query =
from zz in campaign.AsEnumerable()
orderby zz.Field<string>("ID")
select zz;
string whereClause = "zz.Field<string>(\"Product\") in ('EWH','HEC')";
query = query.Where(whereClause);
DataTable sublist = query.CopyToDataTable<DataRow>();
}
But it gives me an error on line: query = query.Where(whereClause), saying
No property or field 'zz' exists in type 'DataRow'".
If I changed to:
string whereClause = "Product in ('EWH','HEC')"; it will say:
No property or field 'Product' exists in type 'DataRow'
Can anyone help me on how to solve this problem? I feel it could be a pretty simple syntax change, but I just don't know at this time.
First, this line has an error
orderby zz.Field<string>("ID")
because as you said, your ID column is of type int.
Second, you need to learn LINQ query syntax. Forget about strings, the same way you used from, orderby, select in the query, you can also use where and many other operators. Also you'll need to learn the equivalent LINQ constructs for SQL-ish things, like for instance IN (...) is mapped to Enumerable.Contains etc.
With all that being said, here is your query
var productFilter = new[] { "EWH", "HEC" };
var query =
from zz in campaign.AsEnumerable()
where productFilter.Contains(zz.Field<string>("Product"))
orderby zz.Field<int>("ID")
select zz;
Update As per your comment, if you want to make this dynamic, then you need to switch to lambda syntax. Multiple and criteria can be composed by chaining multiple Where clauses like this
List<string> productFilter = ...; // coming from outside
List<string> channelFilter = ...; // coming from outside
var query = campaign.AsEnumerable();
// Apply filters if needed
if (productFilter != null && productFilter.Count > 0)
query = query.Where(zz => productFilter.Contains(zz.Field<string>("Product")));
if (channelFilter != null && channelFilter.Count > 0)
query = query.Where(zz => channelFilter.Contains(zz.Field<string>("Channel")));
// Once finished with filtering, do the ordering
query = query.OrderBy(zz => zz.Field<int>("ID"));
I have four tables, with Date data type for the fields startingDate, EndingDate, and ApplyingDate.
I am using ADO.net Entity Framework.
I have written the following query to get the results, but I am getting the dates with the time, and I want only the date part.
I have used EntityFunctions.TuncateTime, but I am still getting same results.
Could anyone please suggest me, how to Get the date only ?
var leaveList = (from application in db.tbl_ApplicationData
join employee in db.tbl_EmployeeDetails
on application.UserName equals employee.UserName
join leaveType in db.tbl_LeaveType
on application.LeaveTypeId equals leaveType.LeaveTypeId
join status in db.tbl_Status
on application.ApplicationStatusId equals status.StatusId
where application.UserName == "100083"
select new
{
EmployeeName = employee.EmployeeName,
LeaveTypeID = leaveType.LeaveTypeName,
StartingDate = EntityFunctions.TruncateTime(application.StartingDate),
EndingDate = EntityFunctions.TruncateTime(application.EndingDate),
AppliedDate = EntityFunctions.TruncateTime(application.ApplyingDate),
NoOfDays = application.NoOfDays,
LeavePurpose = application.LeavePurpose,
LeaveStatus = status.StatusName
});
If your entity model is a System.DateTime, you can just use the DateTime methods when you are using your object:
select new {
EndingDate = application.EndingDate
};
var myValue = leaveList.EndingDate.Date;
Or if you want a string:
leaveList.EndingDate.ToShortDateString()
Is there any Inbuilt function in Linq to Print the month Name while working with LINQPAD?
I want to print the month name in the following Scenario
var query = from e in Employees
let month=e.BirthDate.GetValueOrDefault()
let birthmonth=month.ToString("MMMM")
select birthmonth;
query.Dump();
When I run this it is throwing NotSupportedException.
how to print the month name in Linq to Sql?
Rather than using ToString, try string.Format. Something like:
var query = (from e in Employees
let month = e.BirthDate.GetValueOrDefault()
let birthmonth = string.Format("{0:MMMM}", month)
select birthmonth);
query.Dump();
This seems to work from my local testing, although it is not included as part of the SQL query.
Do it in two steps, one to get the months from the database, then another using Linq-To-Objects to perform the formatting.
var birthDates = Employees.Select(e => e.BirthDate).ToList();
var query = birthDates.Select(d => d != null ? d.ToString("MMMM") : "Null");
query.Dump();
Whatever ORM you are using can't convert the string formatting part of you query into SQL that works on your database. So, doing it in two steps and using ToList to evaluate inbetween overcomes that problem.
I have a linq Entity called Enquiry, which has a property: string DateSubmitted.
I'm writing an app where I need to return IQueryable for Enquiry that have a DateSubmitted within a particular date range.
Ideally I'd like to write something like
IQueryable<Enquiry> query = Context.EnquirySet.AsQueryable<Enquiry>();
int dateStart = int.Parse("20090729");
int dateEnd = int.Parse("20090930");
query = (from e in query
where(enq => int.Parse(enq.DateSubmitted) < dateEnd)
where(enq => int.Parse(enq.DateSubmitted) > dateStart)
select e);
Obviously Linq to EF doesn't recognise int.Parse, so I think I can achieve what I want with an Expression method that returns a predicate???
I've been playing around with PredicateBuilder and looking all over but I've successfully fried my brains trying to work this out. Sure I could add another property to my Entity and convert it there but I'd really like to understand this. Can anyone explain or give an example/link that doesn't fry my brains?
Thanks in advance
Mark
If you know your date strings are valid, and they're really in that order (which is a natural sort order) you might be able to get away with string comparisons:
IQueryable<Enquiry> query = Context.EnquirySet.AsQueryable<Enquiry>();
string dateStart ="20090729";
string dateEnd = "20090930";
query = (from e in query
where(enq => enq.DateSubmitted.CompareTo(dateEnd)) < 0)
where(enq => enq.DateSubmitted.CompareTo(dateStart)) > 0)
select e);