I am tring to get a list of dates from my db that will eventually be used to populate a calendar. Each 'calendar event' has a start date & end date, i need to get all dates between & including the start & end date.
i am stuck on the WHERE statement, as i am not sure what to use for this
public List<EventFeed> GetCalendarDates()
{
return (from eventsList in GetEventsList()
select new EventFeed()
{
//EventDate = todo
}).ToList();
}
UPDATE
just to be clear, if i have a calendar event called foobar which starts on 22/08/2010 and ends on 24/08/2010, then i want my list return:
22/08/2010,
23/08/2010,
24/08/2010
thanks
kb
I had to do something similar recently, I used a Func<> to extract the dates from the range and used the result in the linq query.
I have added the same Func to your Linq query below. You didn't specify the name of the object that is returned by GetEventsList() so just replace the EventItem type for the first type parameter in the Func<> with whatever type you need.
public static List<EventFeed> GetCalendarDates()
{
Func<EventItem, List<DateTime>> extractEventDates = eventItem =>
{
var dates = new List<DateTime>();
for (var date = eventItem.StartDate;
date <= eventItem.EndDate;
date = date.AddDays(1))
{
dates.Add(date);
}
return dates;
};
return (from eventItem in GetEventsList()
from eventDate in extractEventDates(eventItem)
select new EventFeed
{
EventDate = eventDate
}).ToList();
}
You mean you want to select all the events that started on or after start date and ended on or before end date!
If yes, then this will help
var query = from #event in events
where #event.Start.Date >= startDate.Date
&& #event.End.Date <= endDate.Date
select #event;
Related
var result=(from refridgerators in context.A
group refridgerators by new { refridgerators.Id, refridgerators.Name } into gr
select new DAO<String>
{
Key = gr.Key.Name,
Count = gr.Count()
}).OrderByDescending(k => k.Count).Take(numberOfRecords).ToList();
This is my linq to sql query this is working perfectly fine.
this shows top 5 records (sorted by their count) if i pass numberOfRecords =5.
now my problem is i don`t want to modify query. so what should i do in above query to show all records. This is in relation with my requirement i want to use same query to show all refridgerators and Top 5 , top 10 refridgerators.
I am not sure if it is possible using LINQ. but i guess there must be something related to this.
I would simply don't add the Take to the query but to the code where you consume this query.
So for example:
public static IEnumerable<DAO> GetRefrigerators()
{
var query = from refridgerators in context.A
group refridgerators by new { refridgerators.Id, refridgerators.Name } into gr
select new DAO<String>
{
Key = gr.Key.Name,
Count = gr.Count()
};
return query.OrderByDescending(k => k.Count);
}
Now you can either use:
var refrigerators = GetRefrigerators().Take(5).ToList();
or
var refrigerators = GetRefrigerators().Take(10).ToList();
or
var refrigerators = GetRefrigerators().ToList();
I'd make numberOfRecords a int? and if the value is null you should not call Take(numberOfRecords)
var result = (from refridgerators in context.A
group refridgerators by new { refridgerators.Id, refridgerators.Name } into gr
select new DAO<String>
{
Key = gr.Key.Name,
Count = gr.Count()
}).OrderByDescending(k => k.Count);
if(numberOfRecords.HasValue)
result = result.Take(numberOfRecords.Value);
return result.ToList();
I know it changes your query a little bit but I believe it is pretty acceptable, adding a numberOfRecords of a super high value adds an overheard to your query which isn't useful in your case.
So this post is very old, I know, but my solution is not provided (maybe someone wants to achieve the same after 2 years, like me):
You could create your own extension-method that also works with linq 2 sql. Example:
public static class LinqExtensions
{
public static IEnumerable<TResult> TakeIfNotNull<TResult>(this IEnumerable<TResult> source, int? count)
{
return !count.HasValue ? source : source.Take(count.Value);
}
}
this takes an int? instead of int and returns either the source-enumerable if count is null else it returns the result of default Take-method.
So you could write like:
.OrderByDescending(k => k.Count).TakeIfNotNull(numberOfRecords).ToList();
if numberOfCounts is null, it'll take all records.
As the right solution has already been posted by Tim, still I want your attention to the simpler solution, if suits to your requirement.
Add one more if condition at the top of this query.
if(allRecordRequired)
{
numberOfRecords = 2000000;
}
Leave your query as it is.
Pass a huge number to your method.A number that is equal (at least) or bigger than the items count.That should give you all records.
I have a datetime field in a database which when retrieved should only display the date without the time. Can you please let me know how to do it? Here is the query I wrote:
var queryProductEventCustomers = (from r in DbContext.ProductEventCustomers
from s in DbContext.CustomerProducts
where r.Customers_Id == customerID && r.Customers_Id
== s.Customers_Id && s.Products_Id == productID
select new
{
r.Id,
r.Customers_Id,
r.StartTime
The starttime is a datetime field. So, can you please let me know how to do it?
Use the Short Date format:
r.StartTime.ToString("d", DateTimeFormatInfo.InvariantInfo)
http://msdn.microsoft.com/en-us/library/az4se3k1.aspx
The link shows you how to work with all standard date and time formats.
Use the ToShortDateString() method on DateTime.
select new
{
Id = r.Id,
Customers_Id = r.Customers_Id,
Date = r.StartTime.ToShortDateString()
}
Just choose the date portion:
select new
{
Id = r.Id,
Cust_id = r.Customers_Id,
Date = r.StartTime.Date
}
Try this
select new
{
ID = r.Id,
CustomerID = r.Customers_Id,
StartDate = r.StartTime.ToString("dd/MM/yyyy")
}
In my code I have the following Linq Query:
IQueryable<Data> charts = (from report in ctx.Charts group report by new
{
Name = report.ChartTitle.ChartType.ChartCategory.CategoryName,
id = report.ChartTitle.ChartType.ChartCategory.ChartCategoryId,
Period = report.Period
} into d
select new Data
{
Name = d.Key.Name,
Id = d.Key.id,
Period = d.Key.Period,
Reports = from r in d group r by new
{ Title = r.ChartTitle.Name, id = r.ChartTitle.ChartTitleId } into rs
select new Report
{
Title = rs.Key.Title,
Id = rs.Key.id,
Charts = (from c in rs group c by new
{
ChartId = c.ChartId,
FiscalYear = c.FiscalYear,
ModifiedDate = c.ChartView.ModifiedDate,
Function = c.Function.DisplayName,
ChartData=c.ChartView.ViewData
} into cs
select new ChartInfo
{
ChartId = cs.Key.ChartId,
FiscalYear = cs.Key.FiscalYear,
ModifiedDate = cs.Key.ModifiedDate,
Function = cs.Key.Function,
ChartData=cs.Key.ChartData
})
}});
In the above code if I exclude the "ChartData" field (which is of XML datatype), the query executes fine. But when ever I include this field it throws the following error :"The xml data type cannot be selected as DISTINCT because it is not comparable."
Let me know what I am missing here?
You can't group by XML types. This is a SQL restriction, not a LINQ-to-SQL retriction. (See Group by on XML column field with LINQ and select an xml type column in select query with group by SQL Server 2008)
Do you need to group by the XML column? The alternative would be to group by your other columns and then select the first XML value as a result.
Charts = (from c in rs group c by new
{
ChartId = c.ChartId,
FiscalYear = c.FiscalYear,
ModifiedDate = c.ChartView.ModifiedDate,
Function = c.Function.DisplayName,
} into cs
select new ChartInfo
{
ChartId = cs.Key.ChartId,
FiscalYear = cs.Key.FiscalYear,
ModifiedDate = cs.Key.ModifiedDate,
Function = cs.Key.Function,
ChartData=cs.Value.FirstOrDefault().ChartData
})
When using LINQ-to-SQL the items being grouped are still accessible - you don't need to include every 'selected' property / column in the group by` clause like you would in SQL.
You did not tell us what is the actual datatype of the ChartData, but from the error you are describing it looks like the problem is that whatever this datatype is it does not implement the IComparable interface which is a required interface if you want instances of the datatype to be comparable
I'm breaking my head with this and decided to share my problem with you
I want to create an anonymous select from several tables, some of them may contain more than one result. i want to concatenate these results into one string
i did something like this:
var resultTable = from item in dc.table
select new
{
id= item.id,
name= CreateString((from name in item.Ref_Items_Names
select name.Name).ToList()),
};
and the CreateString() is:
private string CreateString(List<string> list)
{
StringBuilder stringedData = new StringBuilder();
for (int i = 0; i < list.Count; i++)
{
stringedData.Append(list[i] + ", ");
}
return stringedData.ToString();
}
my intentions were to convert the "name" query to list and then sent it to CreateString() to convert it to one long concatenated string.
I tried using .Aggregate((current,next) => current + "," + next);
but when i try to convert my query to DataTable like below:
public DataTable ToDataTable(Object query)
{
DataTable dt = new DataTable();
IDbCommand cmd = dc.GetCommand(query as IQueryable);
SqlDataAdapter adapter = new SqlDataAdapter();
adapter.SelectCommand = (SqlCommand)cmd;
cmd.Connection.Open();
adapter.Fill(dt);
cmd.Connection.Close();
return dt;
}
I'm getting exception that "dc.GetCommand()" can't understand query with Aggregate method
later I tried to even use this simple query:
var resultTable = from itemin dc.table
select new
{
name = CreateString()
};
When CreateString() returns "success", nothing was inserted to "name"
why there is no way of using methods in select clause?
Thank you
Yotam
There is difference between LINQ to objects and LINQ to some-db-provider. Generally speaking, when using IQueryable, you can't use any methods, except the ones your provider understands.
What you can do is to retrieve the data from the database and then do the formatting using LINQ to objects:
var data = from item in dc.table
where /* some condition */
select item;
var result = from item in data.AsEnumerable()
select new
{
name = SomeFunction(item)
}
The AsEnumerable() extension method forces processing using LINQ to objects.
Forgive me if I've miss interpreted your question. It seems that what you are trying to do is abstract your select method for reuse. If this is the case, you may consider projection using a lambda expression. For example:
internal static class MyProjectors
{
internal static Expression<Func<Object1, ReturnObject>> StringDataProjector
{
get
{
return d => new Object1()
{
//assignment here
}
}
}
}
Now you can select your datasets as such:
dc.Table.Select(MyProjectors.StringDataProjector)
As for the concatenation logic, what about selecting to some base class with an IEnumerable<string> property and a read-only property to handle the concatenation of the string?
I am having some trouble with a linq query I am trying to write.
I am trying to use the repository pattern without to much luck. Basically I have a list of transactions and a 2nd list which contains the description field that maps against a field in my case StoreItemID
public static IList<TransactionViewModel> All()
{
var result = (IList<TransactionViewModel>)HttpContext.Current.Session["Transactions"];
if (result == null)
{
var rewardTypes = BusinessItemRepository.GetItemTypes(StoreID);
HttpContext.Current.Session["Transactions"] =
result =
(from item in new MyEntities().TransactionEntries
select new TransactionViewModel()
{
ItemDescription = itemTypes.FirstOrDefault(r=>r.StoreItemID==item.StoreItemID).ItemDescription,
TransactionDate = item.PurchaseDate.Value,
TransactionAmount = item.TransactionAmount.Value,
}).ToList();
}
return result;
}
public static List<BusinessItemViewModel>GetItemTypes(int storeID)
{
var result = (List<BusinessItemViewModel>)HttpContext.Current.Session["ItemTypes"];
if (result == null)
{
HttpContext.Current.Session["ItemTypes"] = result =
(from items in new MyEntities().StoreItems
where items.IsDeleted == false && items.StoreID == storeID
select new BusinessItemViewModel()
{
ItemDescription = items.Description,
StoreID = items.StoreID,
StoreItemID = items.StoreItemID
}).ToList();
}
return result;
However I get this error
Unable to create a constant value of type 'MyMVC.ViewModels.BusinessItemViewModel'. Only primitive types ('such as Int32, String, and Guid') are supported in this context.
I know its this line of code as if I comment it out it works ok
ItemDescription = itemTypes.FirstOrDefault(r=>r.StoreItemID==item.StoreItemID).ItemDescription,
How can I map ItemDescription against my list of itemTypes?
Any help would be great :)
This line has a problem:
ItemDescription = itemTypes.FirstOrDefault(r=>r.StoreItemID==item.StoreItemID)
.ItemDescription,
Since you are using FirstOrDefault you will get null as default value for a reference type if there is no item that satifies the condition, then you'd get an exception when trying to access ItemDescription - either use First() if there always will be at least one match or check and define a default property value for ItemDescription to use if there is none:
ItemDescription = itemTypes.Any(r=>r.StoreItemID==item.StoreItemID)
? itemTypes.First(r=>r.StoreItemID==item.StoreItemID)
.ItemDescription
: "My Default",
If itemTypes is IEnumerable then it can't be used in your query (which is what the error message is telling you), because the query provider doesn't know what to do with it. So assuming the that itemTypes is based on a table in the same db as TransactionEntities, then you can use a join to achieve the same goal:
using (var entities = new MyEntities())
{
HttpContext.Current.Session["Transactions"] = result =
(from item in new entities.TransactionEntries
join itemType in entities.ItemTypes on item.StoreItemID equals itemType.StoreItemID
select new TransactionViewModel()
{
ItemDescription = itemType.ItemDescription,
TransactionDate = item.PurchaseDate.Value,
TransactionAmount = item.TransactionAmount.Value,
CustomerName = rewards.CardID//TODO: Get customer name
}).ToList();
}
I don't know the structure of your database, but hopefully you get the idea.
I had this error due a nullable integer in my LINQ query.
Adding a check within my query it solved my problem.
query with problem:
var x = entities.MyObjects.FirstOrDefault(s => s.Obj_Id.Equals(y.OBJ_ID));
query with problem solved:
var x = entities.MyObjects.FirstOrDefault(s => s.Obj_Id.HasValue && s.Obj_Id.Value.Equals(y.OBJ_ID));