I'm moving some code from a traditional worker role to an Azure Function. I've found a line of code that returns a result when I call it from a console app, but null when I call it from a function.
Now, for some example code. I wrote a _resultProvider class that basically queries an underlying CosmosDB database -- at the base class, it creates an IOrderedQueryable query and filters it based on the predicate that you pass in as a parameter. The first line of code returns a result only when I call it from a console app, and null if I call it from an Azure Function. The second line returns a result from either platform.
Gets result when called from the worker role, but null when called from the function:
var res1 = _resultProvider.GetSpecialAsync(o => id == o.Id).Result.FirstOrDefault();
Gets result from either the worker role or the function:
var res2 = _resultProvider.GetSpecialAsync(o => 1 == 1).Result.Where(o=>id==o.Id).FirstOrDefault();
I'm guessing this is some kind of LINQ issue, because passing the predicate along doesn't seem to work from the function, but it works if I just get all the results and query that result set.
Here's the GetSpecialAsync code:
public async Task<IEnumerable<T>> GetItemsSpecialAsync(Expression<Func<T, bool>> predicate)
{
IDocumentQuery<T> query = client.CreateDocumentQuery<T>(
UriFactory.CreateDocumentCollectionUri(DatabaseId, CollectionId),
new FeedOptions { MaxItemCount = -1, EnableCrossPartitionQuery = true})
.Where(predicate)
.AsDocumentQuery();
List<T> results = new List<T>();
while (query.HasMoreResults)
{
results.AddRange(await query.ExecuteNextAsync<T>());
}
return results;
}
Here's the type I'm attempting to return, ResultDocVm:
public class ResultDocVm : DocViewModelBase
{
public string Name { get; set; }
public long AccountId { get; set; }
// ... insert more junk here with getters and setters
}
Here's DocViewModelBase:
public abstract class DocViewModelBase
{
[JsonProperty(PropertyName = "id")]
public string Id { get; set; }
public DateTime? CreatedAt { get; set; }
//... even more junk here
}
So after all the back and forth it looks like the Console App is taking the JsonProperty attribute into account while the Azure Function doesn't.
This generates a query which will return no results because the Id property will be uppercased and not lowercased ie id.
It sounds like a bug with the Azure Function at the Azure level and not with your code per se.
Related
I have this very weird problem that I cannot get my head around. Perhaps someone could point out what I am doing wrong.
Basically, I am just trying to search items using Linq to Sitecore.
So, my classes look like ( I am using glass too)
[SitecoreType(TemplateId = "{TEMPLATE_GIUD}")]
public class MyMappedClass : SharedFieldClass
{
[SitecoreField(FieldName = "mylist")]
public virtual IEnumerable<SharedFieldClass> MyMultilistField { get; set; }
[SitecoreField(FieldName = "field1")]
[IndexField("field1")]
public virtual MyKeyValue field1 { get; set; }
}
[SitecoreType]
public class MyKeyValue
{
public virtual Sitecore.Data.ID Id {get;set;}
public virtual string MyValue{get;set;}
}
So when I do the below query it works as it's supposed to.
var results = context.GetQueryable<SearchResultItem>()
.Where(c => ((string)c["field1"]) == "{GUID}").GetResults();
But, when I do the below it returns 0 result.
List<MyMappedClass> results = context.GetQueryable<MyMappedClass>()
.Where(c => c.field1.MyValue == "{GUID}").ToList();
I have read this link . And I have followed the 2nd process described here for Glass to work with Sitecore7 Search (the "SharedFieldClass" contains all the basic index fields).
This is a pretty obvious scenario and I'm sure lots of people have done it already and I am doing something silly here.
Thanks in advance.
/## EDIT ##/
Okay so I've done a bit more digging on this. Not sure if it's a bug in ContentSearch/Luncene.NET API or I am missing something BUT seems like what was posted here is probably not TRUE and if you have a complex field type ( which you will ) you can not query with a mapped class against Lucene. ( not sure if this is also the case for Solr). If you are doing search against simple type like string and int then it works like a charm.
SO here're my findings:
After enabling DEBUG and LOG on for contentsearch I found that if I query like this context.GetQueryable<MyMappedClass>().Where(c => c.field1.MyValue == "{GUID}") what it gets translated into is DEBUG Executing lucene query: field1.value:7e9ed2ae07194d83872f9836715eca8e and as there's no such thing in the index named "field1.value" the query doesn't return anything. The name of the index is actually just "field1". Is this a bug ??
However, query like this context.GetQueryable<SearchResultItem>() .Where(c => ((string)c["field1"]) == "{GUID}").GetResults(); works because it gets translated into "DEBUG Executing lucene query: +field1:7e9ed2ae07194d83872f9836715eca8e".
I also did write a method in my mapped class like below:
public string this[string key]
{
get
{
return key.ToLowerInvariant();
}
set { }
}
Which allowed me write the below query with my MyMappedClass.
results2 = context.GetQueryable<MyMappedClass>().Where(c => c["filed1"]== "{GUID}").ToList();
This returned expected result. BUT the values of the fields in MyMappedClass are not filled ( in fact they're all null except the core/shared values like templateid, url etc which are populated in the filled document). So the result list are pretty much useless. I could do a loop over all of them and manually get the values populated as I have the itemid. But imagine the cost for a large result set.
Lastly I did this:
<fieldType fieldTypeName="droplink" storageType="YES" indexType="TOKENIZED" vectorType="NO" boost="1f" type="System.String" settingType="Sitecore.ContentSearch.LuceneProvider.LuceneSearchFieldConfiguration, Sitecore.ContentSearch.LuceneProvider" />
So this returned populated "field1" with the itemid in lucene query using "IndexViewer2.0". BUT this fails for MyMappedClass too as the value of "field1" in the document is a System.string .. but it is mapped as "MyKeyValue" in MyMappedClass SO it throws the below exception
Exception: System.InvalidCastException
Message: Invalid cast from 'System.String' to 'MyLib.MyKeyValue'.
SO, the big question is:
How does one query using his/her mapped class using the cool ContentSearch API ?
I bit more further digging got me to a working solution. Posting it here just in case anyone runs into this issue.
This is how my "SharedFieldClass" looked like ( which was somewhat wrong )
public abstract class SharedFieldClass
{
[SitecoreId]
[IndexField("_id")]
[TypeConverter(typeof(IndexFieldIDValueConverter))]
public virtual ID Id { get; set; }
[SitecoreInfo(SitecoreInfoType.Language)]
[IndexField("_language")]
public virtual string Language { get; set; }
[SitecoreInfo(SitecoreInfoType.Version)]
public virtual int Version
{
get
{
return Uri == null ? 0 : Uri.Version.Number;
}
}
[TypeConverter(typeof(IndexFieldItemUriValueConverter))]
[XmlIgnore]
[IndexField("_uniqueid")]
public virtual ItemUri Uri { get; set; }
}
And there's a class in Glass that does the mapping. Which looks like below:
var sitecoreService = new SitecoreService("web");
foreach (var r in results)
{
sitecoreService.Map(r);
}
for me this class was failing to map because of this line:
[SitecoreId]
[IndexField("_id")]
[TypeConverter(typeof(IndexFieldIDValueConverter))]
public virtual ID Id { get; set; }
It was throwing a NULL exception at sitecoreService.Map(r); line
So I changed it to below:
[SitecoreId]
[IndexField("_group")]
[TypeConverter(typeof(IndexFieldIDValueConverter))]
public virtual ID Id { get; set; }
And it worked. I'm not sure when the index field for ItemId in sitecore changed from "_id" to "_group" or whether it was always like that. But it is "_group" in the SearchResultItem class. So I used it and mapping was successful.
So to Sum it all the solution looks like this:
The Mapped Class:
[SitecoreType(TemplateId = "{TEMPLATE_GIUD}")]
public class MyMappedClass : SharedFieldClass
{
[SitecoreField(FieldName = "mylist")]
public virtual IEnumerable<SharedFieldClass> MyMultilistField { get; set; }
[SitecoreField(FieldName = "field1")]
[IndexField("field1")]
public virtual MyKeyValue field1 { get; set; }
// Will be set with key and value for each field in the index document
public string this[string key]
{
get
{
return key.ToLowerInvariant();
}
set { }
}
}
[SitecoreType]
public class MyKeyValue
{
public virtual Sitecore.Data.ID Id {get;set;}
public virtual string MyValue{get;set;}
}
And the query is:
List<MyMappedClass> results = context.GetQueryable<MyMappedClass>()
.Where(c => c["field1"] == "{GUID}").ToList();
That's it.
/* edited */
OH!! Wait that's not it. This will still fail to cast the complex type "MyKeyValue" when the "field1" is populated with guid in the index document.
So to avoid this I had to write my custom converter as #Michael Edwards suggested.
I had to modify the class slightly to fit my needs ..
public class IndexFieldKeyValueModelConverter : TypeConverter
{
public override bool CanConvertFrom(ITypeDescriptorContext context, Type sourceType)
{
var config = Glass.Mapper.Context.Default.GetTypeConfiguration<SitecoreTypeConfiguration>(sourceType, true);
if (config != null && sourceType == typeof(MyLib.IKeyValue))
{
return true;
}
else
return base.CanConvertFrom(context, sourceType);
}
public override bool CanConvertTo(ITypeDescriptorContext context, Type destinationType)
{
if (destinationType == typeof(string))
return true;
else
return base.CanConvertTo(context, destinationType);
}
public override object ConvertFrom(ITypeDescriptorContext context, CultureInfo culture, object value)
{
var scContext = new SitecoreContext();
Guid x = Guid.Empty;
if(value is string)
{
x = new Guid((string)value);
}
var item = scContext.Database.GetItem(x.ToString());
if (item == null)
return null;
return scContext.CreateType(typeof(MyLib.IKeyValue), item, true, false, new Dictionary<string, object>());
}
public override object ConvertTo(ITypeDescriptorContext context, CultureInfo culture, object value, Type destinationType)
{
var config = Glass.Mapper.Context.Default.GetTypeConfiguration<SitecoreTypeConfiguration>(value.GetType(), true);
ID id = config.GetId(value);
return id.ToShortID().ToString().ToLowerInvariant();
}
}
Not sure if it were the expected behaviour or not .. but for some reason, in the convertfrom method the value of the "object value" parameter was short string id format. So for scContext.Database.GetItem to work I had to convert it to a proper GUID and then it started returning proper item rather than null.
AND then I wrote my query like this:
results = context.GetQueryable<MyMappedGlassClass>().Where(c => c["field1"] == field1value && c["field2"] == field2value && c["_template"] == templateId).Filter(selector => selector["_group"] != currentId).ToList();
Looks like a fair bit of work to get it to work. I guess using the LinqHelper.CreateQuery method is the easy way out .. but as Mr. Pope suggested here that this method is not be used as this is an internal method.
Not sure what's the balance here.
/* end edited */
Please see my question description section for explanation on why I had to do things this way.
Also, (I bias opinion ) is the trick described here may not be valid anymore (please see my question description's edit section for the reason behind).
Also, index field for itemid in the Glass Mapper tutorial here is I think wrong (unless otherwise proven).
Hope it helps someone saving/wasting time.
You could create a custom field mapper for lucene that would convert from the Guid in the index to a glass model. I hacked this out but I haven't tested it:
public class IndexFieldDateTimeValueConverter : TypeConverter
{
public Type RequestedType { get; set; }
public override bool CanConvertFrom(ITypeDescriptorContext context, Type sourceType)
{
var config = Glass.Mapper.Context.Default.GetTypeConfiguration<SitecoreTypeConfiguration>(sourceType, true);
if (config != null)
{
RequestedType = sourceType;
return true;
}
else
return base.CanConvertFrom(context, sourceType);
}
public override bool CanConvertTo(ITypeDescriptorContext context, Type destinationType)
{
if (destinationType == typeof(string))
return true;
else
return base.CanConvertTo(context, destinationType);
}
public override object ConvertFrom(ITypeDescriptorContext context, CultureInfo culture, object value)
{
var scContext = new SitecoreContext();
return scContext.CreateType(RequestedType, scContext.Database.GetItem(value.ToString()),true, false, new Dictionary<string, object>());
}
public override object ConvertTo(ITypeDescriptorContext context, CultureInfo culture, object value, Type destinationType)
{
var config = Glass.Mapper.Context.Default.GetTypeConfiguration<SitecoreTypeConfiguration>(value.GetType(), true);
ID id =config.GetId(value);
return id.ToShortID().ToString().ToLowerInvariant();
}
My concern is that the ConvertFrom method does not get passed the type requested so we have to store this as property on the class to pass it from the CanConvertFrom method to the ConvertFrom method. This makes this class not thread safe.
Add this to the indexFieldStorageValueFormatter section of the sitecore config.
The problem here is that SearchResultItem is not actually an Item, but does have the GetItem() method to get the Sitecore item. What you need to do is the following:
List<MyMappedClass> results = context.GetQueryable<SearchResultItem>()
.Select(sri => sri.GetItem())
.Where(i => i != null)
.Select(i => i.GlassCast<MyMappedClass>())
.Where(c => c.field1.MyValue == "{GUID}").ToList();
I haven't worked with Glass specifically, but if you change your parent class to SearchResultItem, does it begin working? If so, that would indicate an issue with the SharedFieldClass parent class.
I'm designing an application using ASP.NET Web API and Entity Framework 5 and LINQ to Entities. The Web API doesn't serve up the entities directly, it converts them to a set of data transfer objects that are similar but not identical to my entities. The API will be used by a Silverlight application initially but I will have to support non-.NET clients (e.g. iOS apps) down the road. I'd also like to give the client the ability to run a robust set of queries against the API.
These requirements have lead me to consider the query object pattern. Essentially, I want to create a homegrown query object client-side, post it to the Web API, and convert the query object to a lambda expression that I can use in LINQ to Entities. This last part is what's tripping me up.
Starting with a simple comparison query, I want to be able to convert an object that looks like the following into a lambda expression at runtime.
public enum QueryOperator
{
None = 0,
GreaterThan,
GreaterThanOrEqualTo,
EqualTo,
NotEqualTo,
LessThanOrEqualTo,
LessThan
}
public class SimpleQuery<T>
{
public SimpleQuery()
{
this.Field = null;
this.Operator = QueryOperator.None;
this.Value = null;
}
public string Field { get; set; }
public QueryOperator Operator { get; set; }
public object Value { get; set; }
public IEnumerable<T> Execute(IQueryable<T> queryTarget)
{
// ????
}
}
How can I do this?
I've had to do things like this in the past. Here's what I came up with:
public IEnumerable<T> Execute(IQueryable<T> queryTarget)
{
return queryTarget.Where(this.GetWhereExpression<T>());
}
private Expression<Func<T, bool>> GetWhereExpression<T>()
{
var param = Expression.Parameter(typeof(T), "x");
var prop = Expression.Property(param, this.Field);
var value = Expression.Constant(this.Value, prop.Type);
Expression compare = null;
switch(this.Operator)
{
case QueryOperator.EqualTo:
compare = Expression.Equal(prop, value);
break;
...
}
return Expression.Lambda(compare, param);
}
I am building dynamic linq expressions which is working fine for a single entity.
For example:
I have a class called Employee and empeduinfo
public class Employee
{
public int Id { get; set; }
public string Name { get; set; }
}
public class EmpEduInfo
{
public int Id { get; set; }
public string Name { get; set; }
public int EmpId { get; set; }
}
I need to get all the the employees and empeduinfo class starts with "x"
I prepared expression for startswith("x")
var temp= entities.employees.Include("EmpEduInfo").Where(mydynamicexpression);
In this case it is filtering only parent table not on child.
I need to prepare generic expression so than i need to filter both parent and child objects dynamically.
Without using expression I know a solution:
var temp= (from ee in entities.Employee.Include("EmpEduInfo").Where(x => x.name.StartsWith("t"))
where ee.EmpEduInfo.Where(x => x.name.StartsWith("t")).Count()>0
select ee).ToList();
using expressions I am building generic expression to provide dynamic advance search rather than writing in each and every entity.
Here is my expression details
// Get the method information for the String.StartsWith() method
MethodInfo mi = typeof(string).GetMethod("StartsWith", new Type[] { typeof(string) });
// Build the parameter for the expression
ParameterExpression empparam= Expression.Parameter(typeof(employee), "ename");;
// Build the member that was specified for the expression
MemberExpression field = Expression.PropertyOrField(empparam, "name");
// Call the String.StartsWith() method on the member
MethodCallExpression startsWith = Expression.Call(field, mi, Expression.Constant("t"));
var namelamda = Expression.Lambda<Func<employee, bool>>(startsWith, new ParameterExpression[] { empparam });
var temp = entities.employees.Include("empedudetails").Where(namelamda).ToList();
You can look at the Expression the compiler generates using IQueryable:
IQueryable<Employee> query =
from ee in entities.Employee ...
var expression = query.Expression;
Look at expression in a debugger to see what you need to generate - LINQPad is good for this.
You might want to simplify your query a bit first:
IQueryable<Employee> query =
from ee in entities.Employee.Include("EmpEduInfo")
where
ee.name.StartsWith("t") &&
ee.EmpEduInfo.Any(x => x.name.StartsWith("t"))
select ee;
I was trying in EF 4.0 either we have write DB extentions for the same.
Option is provided in EF 4.1
http://www.asp.net/mvc/tutorials/getting-started-with-ef-using-mvc/reading-related-data-with-the-entity-framework-in-an-asp-net-mvc-application
Thanks.
I am using ASP.NET MVC 3 with Entity Framework 4 using POCOs and want to query a set and select some properties to put into my viewModel. I will sketch a simplified version of my situation:
Situation:
I have an entity BananaTree containing a collection of Banana
public class Banana
{
public int Id { get; set; }
public int Size { get; set; }
public TimeSpan Age { get; set }
public string Description { get; set; }
}
public class BananaTree
{
public int Id { get; set; }
public ICollection<Banana> Bananas { get; set; }
}
I also have a view model BananaListItemViewModel used in the view showing a list of bananas for a certain banana tree. This view is managed by the BananaTreeController
public class BananaListItemViewModel
{
public int Id { get; set; }
public TimeSpan Age { get; set }
}
I have a Details action on the controller like so:
public ActionResult Details(int bananaTreeId)
{
var viewModel = from bananaTree in bananaTreeRepository.BananaTrees
where bananaTree.Id == bananaTreeId
from banana in bananaTree.Bananas
select new BananaListItemViewModel
{
Id = banana.Id,
Age = banana.Age
};
return View(viewModel);
}
What I want to change
This works fine and now I only select the items from the database that I need for my view model. However, I want to take out some more logic from my controller and am trying to do this as much as possible.
I would like to have a function in my repository like so:
IQueryable<Banana> GetBananas(int bananaTreeId)
{
return (from bananaTree in BananaTrees
where bananaTree.Id == bananaTreeId
select bananaTree.Bananas).Single().AsQueryable();
}
and use it like so:
public ActionResult Details(int bananaTreeId)
{
var viewModel = from banana in bananaTreeRepository.GetBananas(bananaTreeId)
select new BananaListItemViewModel
{
Id = banana.Id,
Age = banana.Age
};
return View(viewModel);
}
Question
My question is, in this case, will the two queries be combined and go to the database in one go like in my first example or will this first get all the bananas from the tree completely out of the database and perform the second query on that list? I would prefer the first case. If not, could I rewrite the GetBananas query to get that behaviour (for example like the query below)?
IQueryable<Banana> GetBananas(int bananaTreeId)
{
return from bananaTree in BananaTrees
where bananaTree.Id == bananaTreeId
from banana in bananaTree.Bananas
select banana;
}
Thanks very much in advance.
In your specific case, it will be only one query, if the call to Single() doesn't lead to the query to be executed. Unfortunately, I couldn't find any info on whether it does or does not. The call to AsQueryable does not trigger the execution as long, as the Bananas property really is an IQueryable.
According to http://msdn.microsoft.com/en-us/library/bb156472.aspx, the call to Single doesn't execute your query.
Conclusion:
You code should result in only one query.
In general:
You can pass an IQueryable from one method to another without it being implicitly executed.
The following code will result in only one SQL statement executed at the end, when the call to ToList happens:
IQueryable<Banana> GetBananasByWeight(int weight)
{
return from banana in Bananas where banana.Weight = weight;
}
IQueryable<Banana> FilterByQuality(IQueryable<Banana> bananaQuery, int quality)
{
return bananaQuery.Where(b => b.Quality == quality);
}
public List<Banana> GetBananas(int weight, int quality)
{
var query = GetBananasByWeight(weight);
var filteredBananas = FilterByQuality(query, quality);
return filteredBananas.ToList();
}
The basic problem...
I have a method which executes the following code:
IList<Gig> gigs = GetGigs().WithArtist(artistId).ToList();
The GetGigs() method gets Gigs from my database via LinqToSql...
So, when GetGigs().WithArtist(artistId).ToList() is executed I get the following exception:
Member access 'ListenTo.Shared.DO.Artist Artist' of 'ListenTo.Shared.DO.Act' not legal on type 'System.Collections.Generic.List`1[ListenTo.Shared.DO.Act]
Note that the extension function "WithArtist" looks like this:
public static IQueryable<Gig> WithArtist(this IQueryable<Gig> qry, Guid artistId)
{
return from gig in qry
where gig.Acts.Any(act => (null != act.Artist) && (act.Artist.ID == artistId))
orderby gig.StartDate
select gig;
}
If I replace the GetGigs() method with a method that constructs a collection of gigs in code (rather than from the DB via LinqToSQL) I do NOT get the exception.
So I'm fairly sure the problem is with my LinqToSQl code rather than the object structure.
However, I have NO IDEA why the LinqToSQl version isnt working, so I've included all the associated code below. Any help would be VERY gratefully receivced!!
The LinqToSQL code....
public IQueryable<ListenTo.Shared.DO.Gig> GetGigs()
{
return from g in DBContext.Gigs
let acts = GetActs(g.ID)
join venue in DBContext.Venues on g.VenueID equals venue.ID
select new ListenTo.Shared.DO.Gig
{
ID = g.ID,
Name = g.Name,
Acts = new List<ListenTo.Shared.DO.Act>(acts),
Description = g.Description,
StartDate = g.Date,
EndDate = g.EndDate,
IsDeleted = g.IsDeleted,
Created = g.Created,
TicketPrice = g.TicketPrice,
Venue = new ListenTo.Shared.DO.Venue {
ID = venue.ID,
Name = venue.Name,
Address = venue.Address,
Telephone = venue.Telephone,
URL = venue.Website
}
};
}
IQueryable<ListenTo.Shared.DO.Act> GetActs()
{
return from a in DBContext.Acts
join artist in DBContext.Artists on a.ArtistID equals artist.ID into art
from artist in art.DefaultIfEmpty()
select new ListenTo.Shared.DO.Act
{
ID = a.ID,
Name = a.Name,
Artist = artist == null ? null : new Shared.DO.Artist
{
ID = artist.ID,
Name = artist.Name
},
GigId = a.GigID
};
}
IQueryable<ListenTo.Shared.DO.Act> GetActs(Guid gigId)
{
return GetActs().WithGigID(gigId);
}
I have included the code for the Act, Artist and Gig objects below:
public class Gig : BaseDO
{
#region Accessors
public Venue Venue
{
get;
set;
}
public System.Nullable<DateTime> EndDate
{
get;
set;
}
public DateTime StartDate
{
get;
set;
}
public string Name
{
get;
set;
}
public string Description
{
get;
set;
}
public string TicketPrice
{
get;
set;
}
/// <summary>
/// The Act object does not exist outside the context of the Gig, therefore,
/// the full act object is loaded here.
/// </summary>
public IList<Act> Acts
{
get;
set;
}
#endregion
}
public class Act : BaseDO
{
public Guid GigId { get; set; }
public string Name { get; set; }
public Artist Artist { get; set; }
}
public class Artist : BaseDO
{
public string Name { get; set; }
public string Profile { get; set; }
public DateTime Formed { get; set; }
public Style Style { get; set; }
public Town Town { get; set; }
public string OfficalWebsiteURL { get; set; }
public string ProfileAddress { get; set; }
public string Email { get; set; }
public ImageMetaData ProfileImage { get; set; }
}
public class BaseDO: IDO
{
#region Properties
private Guid _id;
#endregion
#region IDO Members
public Guid ID
{
get
{
return this._id;
}
set
{
this._id = value;
}
}
}
}
I think the problem is the 'let' statement in GetGigs. Using 'let' means that you define a part of the final query separately from the main set to fetch. the problem is that 'let', if it's not a scalar, results in a nested query. Nested queries are not really Linq to sql's strongest point as they're executed deferred as well. In your query, you place the results of the nested query into the projection of the main set to return which is then further appended with linq operators.
When THAT happens, the nested query is buried deeper into the query which will be executed, and this leads to a situation where the nested query isn't in the outer projection of the query to execute and thus has to be merged into the SQL query ran onto the DB. This is not doable, as it's a nested query in a projection nested inside the main sql query and SQL doesn't have a concept like 'nested query in a projection', as you can't fetch a set of elements inside a projection in SQL, only scalars.
I had the same issue and what seemed to do the trick for me was separating out an inline static method call that returned IQueryable<> so that I stored this deferred query into a variable and referenced that.
I think this is a bug in Linq to SQL but at least there is a reasonable workaround. I haven't tested this out yet but my assumption is that this problem may arise only when referencing static methods of a different class within a query expression regardless of whether the return type of that function is IQueryable<>. So maybe it's the class that holds the method that is at the root of the problem. Like I said, I haven't been able to confirm this but it may be worth investigating.
UPDATE: Just in case the solution isn't clear I wanted to point it out in context of the example from the original post.
public IQueryable<ListenTo.Shared.DO.Gig> GetGigs()
{
var acts = GetActs(g.ID); // Don't worry this call is deferred
return from g in DBContext.Gigs
join venue in DBContext.Venues on g.VenueID equals venue.ID
select new ListenTo.Shared.DO.Gig
{
ID = g.ID,
Name = g.Name,
Acts = new List<ListenTo.Shared.DO.Act>(acts),
Description = g.Description,
StartDate = g.Date,
EndDate = g.EndDate,
IsDeleted = g.IsDeleted,
Created = g.Created,
TicketPrice = g.TicketPrice,
Venue = new ListenTo.Shared.DO.Venue {
ID = venue.ID,
Name = venue.Name,
Address = venue.Address,
Telephone = venue.Telephone,
URL = venue.Website
}
};
}
Note that while this should correct the issue at hand there also seems to be another issue in that the deferred acts query is being accessed in each element of the projection which I would guess would cause separate queries to be issued to the database per row in the outer projection.
I don't see anything in your classes to indicate how LINQ to SQL is meant to work out which column is which, etc.
Were you expecting the WithArtist method to be executed in .NET, or converted into SQL? If you expect it to be converted into SQL, you'll need to decorate your Gig class with appropriate LINQ to SQL attributes (or configure your data context some other way). If you want it to be executed in code, just change the first parameter type from IQueryable<Gig> to IEnumerable<Gig>.
I found out that an issue like this (which I also had recently) can be resolved, if you convert the IQueryable (or Table) variable Gigs into a list like so
return from g in DBContext.Gigs.ToList()
...
If that still doesn't work, do the same for all the IQueryables. The reason behind seems to me that some queries are too complex to be translated into SQL. But if you "materialize" it into a list, you can do every kind of query.
Be careful, you should add "filters" (where conditions) early because too much memory consumption can become a problem.