We Keep Coding

Entity Framework Core: NullReferenceException after DropTable

I am simply trying to drop a table.
First I tried to just remove all the references to the table in the code. When creating a new migration, I get a "NullReferenceException", as shown here.
Then I tried instead to create an empty migration with migrationBuilder.DropTable("MyTable") in the Up() method. That drops the table, but if I try to make a new empty migration I get the same error.
Are these not the ways to drop a table with EF Core? Do I need something else, or doing something in the wrong order?
I am using F#, but I hope that is not the problem.
Build started...
Build succeeded.
System.NullReferenceException: Object reference not set to an instance of an object.
at Microsoft.EntityFrameworkCore.Migrations.Internal.MigrationsModelDiffer.Initialize(ColumnOperation columnOperation, IColumn column, RelationalTypeMapping typeMapping, Boolean isNullable, IEnumerable`1 migrationsAnnotations, Boolean inline)
at Microsoft.EntityFrameworkCore.Migrations.Internal.MigrationsModelDiffer.Add(IColumn target, DiffContext diffContext, Boolean inline)+MoveNext()
at Pomelo.EntityFrameworkCore.MySql.Migrations.Internal.MySqlMigrationsModelDiffer.PostFilterOperations(IEnumerable`1 migrationOperations)+MoveNext()
at System.Linq.Enumerable.SelectManySingleSelectorIterator`2.MoveNext()
at System.Linq.Enumerable.CastIterator[TResult](IEnumerable source)+MoveNext()
at System.Collections.Generic.List`1.InsertRange(Int32 index, IEnumerable`1 collection)
at Microsoft.EntityFrameworkCore.Migrations.Internal.MigrationsModelDiffer.Add(ITable target, DiffContext diffContext)+MoveNext()
at Pomelo.EntityFrameworkCore.MySql.Migrations.Internal.MySqlMigrationsModelDiffer.PostFilterOperations(IEnumerable`1 migrationOperations)+MoveNext()
at Microsoft.EntityFrameworkCore.Migrations.Internal.MigrationsModelDiffer.DiffCollection[T](IEnumerable`1 sources, IEnumerable`1 targets, DiffContext diffContext, Func`4 diff, Func`3 add, Func`3 remove, Func`4[] predicates)+MoveNext()
at System.Linq.Enumerable.ConcatIterator`1.MoveNext()
at Pomelo.EntityFrameworkCore.MySql.Migrations.Internal.MySqlMigrationsModelDiffer.PostFilterOperations(IEnumerable`1 migrationOperations)+MoveNext()
at Microsoft.EntityFrameworkCore.Migrations.Internal.MigrationsModelDiffer.Sort(IEnumerable`1 operations, DiffContext diffContext)
at Microsoft.EntityFrameworkCore.Migrations.Internal.MigrationsModelDiffer.GetDifferences(IRelationalModel source, IRelationalModel target)
at Microsoft.EntityFrameworkCore.Migrations.Design.MigrationsScaffolder.ScaffoldMigration(String migrationName, String rootNamespace, String subNamespace, String language)
at Microsoft.EntityFrameworkCore.Design.Internal.MigrationsOperations.AddMigration(String name, String outputDir, String contextType, String namespace)
at Microsoft.EntityFrameworkCore.Design.OperationExecutor.AddMigrationImpl(String name, String outputDir, String contextType, String namespace)
at Microsoft.EntityFrameworkCore.Design.OperationExecutor.AddMigration.<>c__DisplayClass0_0.<.ctor>b__0()
at Microsoft.EntityFrameworkCore.Design.OperationExecutor.OperationBase.<>c__DisplayClass3_0`1.<Execute>b__0()
at Microsoft.EntityFrameworkCore.Design.OperationExecutor.OperationBase.Execute(Action action)
Object reference not set to an instance of an object.

how to fix this query of sql

Address TableUserTableThis Query is working perfectly fine in SQL Server Management Studio.
But when I am trying to run this query in C# it gives an exception please help me.
I Have tried many things but unable to resolve this problem.
SQL QUERY
set #LATITUDE=12
set #LONGITUDE=12
Select * FROM [ChefODine].[dbo].[User] Inner Join [ChefODine].[dbo].[Address] on [ChefODine].[dbo].[User].AID=Address.ID
WHERE AID IN (
SELECT Top 5 ID
FROM [ChefODine].[dbo].[Address]
ORDER BY (ABS(ABS(LAT)-ABS(#LATITUDE)))+ABS(ABS(Lng)-ABS(#LONGITUDE)))
C# CODE
public HttpResponseMessage getNearByChef(double lat, double lng)
{
var user = db.Users.SqlQuery("Select * FROM [ChefODine].[dbo].[User] Inner Join [ChefODine].[dbo].[Address] on [ChefODine].[dbo].[User].AID=Address.ID WHERE AID IN( SELECT Top 5 ID FROM[ChefODine].[dbo].[Address] ORDER BY(ABS(ABS(LAT) - ABS("+lat+"))) + ABS(ABS(Lng) - ABS("+lng+"))) ");
return Request.CreateResponse(HttpStatusCode.OK,user);
}
Here is the Exception:
"Message": "An error has occurred.",
"ExceptionMessage": "The 'ObjectContent'1' type failed to serialize the response body for content type 'application/json; charset=utf-8'.",
"ExceptionType": "System.InvalidOperationException",
"StackTrace": null,
"InnerException": {
"Message": "An error has occurred.",
"ExceptionMessage": "The data reader is incompatible with the specified 'ChefODineModel.User'. A member of the type, 'Date_time', does not have a corresponding column in the data reader with the same name.",
"ExceptionType": "System.Data.Entity.Core.EntityCommandExecutionException",
"StackTrace": " at System.Data.Entity.Core.Query.InternalTrees.ColumnMapFactory.GetMemberOrdinalFromReader(DbDataReader storeDataReader, EdmMember member, EdmType currentType, Dictionary'2 renameList)\r\n at System.Data.Entity.Core.Query.InternalTrees.ColumnMapFactory.GetColumnMapsForType(DbDataReader storeDataReader, EdmType edmType, Dictionary'2 renameList)\r\n at System.Data.Entity.Core.Query.InternalTrees.ColumnMapFactory.CreateColumnMapFromReaderAndType(DbDataReader storeDataReader, EdmType edmType, EntitySet entitySet, Dictionary'2 renameList)\r\n at System.Data.Entity.Core.Objects.ObjectContext.InternalTranslate[TElement](DbDataReader reader, String entitySetName, MergeOption mergeOption, Boolean streaming, EntitySet& entitySet, TypeUsage& edmType)\r\n at System.Data.Entity.Core.Objects.ObjectContext.ExecuteStoreQueryInternal[TElement](String commandText, String entitySetName, ExecutionOptions executionOptions, Object[] parameters)\r\n at System.Data.Entity.Core.Objects.ObjectContext.<>c__DisplayClass65'1.b__64()\r\n at System.Data.Entity.Core.Objects.ObjectContext.ExecuteInTransaction[T](Func'1 func, IDbExecutionStrategy executionStrategy, Boolean startLocalTransaction, Boolean releaseConnectionOnSuccess)\r\n at System.Data.Entity.Core.Objects.ObjectContext.<>c__DisplayClass65'1.b__63()\r\n at System.Data.Entity.SqlServer.DefaultSqlExecutionStrategy.Execute[TResult](Func'1 operation)\r\n at System.Data.Entity.Core.Objects.ObjectContext.ExecuteStoreQueryReliably[TElement](String commandText, String entitySetName, ExecutionOptions executionOptions, Object[] parameters)\r\n at System.Data.Entity.Core.Objects.ObjectContext.ExecuteStoreQuery[TElement](String commandText, String entitySetName, ExecutionOptions executionOptions, Object[] parameters)\r\n at System.Data.Entity.Internal.Linq.InternalSet'1.<>c__DisplayClass11.b__10()\r\n at System.Data.Entity.Internal.LazyEnumerator'1.MoveNext()\r\n at Newtonsoft.Json.Serialization.JsonSerializerInternalWriter.SerializeList(JsonWriter writer, IEnumerable values, JsonArrayContract contract, JsonProperty member, JsonContainerContract collectionContract, JsonProperty containerProperty)\r\n at Newtonsoft.Json.Serialization.JsonSerializerInternalWriter.SerializeValue(JsonWriter writer, Object value, JsonContract valueContract, JsonProperty member, JsonContainerContract containerContract, JsonProperty containerProperty)\r\n at Newtonsoft.Json.Serialization.JsonSerializerInternalWriter.Serialize(JsonWriter jsonWriter, Object value, Type objectType)\r\n at Newtonsoft.Json.JsonSerializer.SerializeInternal(JsonWriter jsonWriter, Object value, Type objectType)\r\n at System.Net.Http.Formatting.BaseJsonMediaTypeFormatter.WriteToStream(Type type, Object value, Stream writeStream, Encoding effectiveEncoding)\r\n at System.Net.Http.Formatting.JsonMediaTypeFormatter.WriteToStream(Type type, Object value, Stream writeStream, Encoding effectiveEncoding)\r\n at System.Net.Http.Formatting.BaseJsonMediaTypeFormatter.WriteToStream(Type type, Object value, Stream writeStream, HttpContent content)\r\n at System.Net.Http.Formatting.BaseJsonMediaTypeFormatter.WriteToStreamAsync(Type type, Object value, Stream writeStream, HttpContent content, TransportContext transportContext, CancellationToken cancellationToken)\r\n--- End of stack trace from previous location where exception was thrown ---\r\n at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)\r\n at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n at System.Web.Http.WebHost.HttpControllerHandler.d__1b.MoveNext()"

"The data reader is incompatible with the specified
'ChefODineModel.User'. A member of the type, 'Date_time', does not
have a corresponding column in the data reader with the same name.",
The user object cannot be mapped with ChefODineModel.User because date_time doesn't exist in the Dto Model.
beside that you can use SqlParameter when you have to pass data into the query
public HttpResponseMessage getNearByChef(double lat, double lng)
{
string query = #"Select u.* FROM [ChefODine].[dbo].[User] u
Inner Join [ChefODine].[dbo].[Address] on [ChefODine].[dbo].[User].AID=Address.ID
WHERE AID IN( SELECT Top 5 ID FROM[ChefODine].[dbo].[Address] ORDER BY(ABS(ABS(LAT) - ABS(#LATITUDE))) + ABS(ABS(LATITUDE) - ABS(#LONGITUDE)))";
var user = db.Users.SqlQuery(query, new SqlParameter("#LATITUDE", lat), new SqlParameter("#LONGITUDE", lng)).ToList();
return Request.CreateResponse(HttpStatusCode.OK, user);
}

Dapper throws "Invalid type owner for DynamicMethod."

So I'm trying to use Dapper.net and I'm liking it. What I'm not liking is when I try to batch-insert entities and I get the following error thrown:
Invalid type owner for DynamicMethod.
at System.Reflection.Emit.DynamicMethod.Init(String name,
MethodAttributes attributes, CallingConventions callingConvention,
Type returnType, Type[] signature, Type owner, Module m, Boolean
skipVisibility, Boolean transparentMethod, StackCrawlMark& stackMark)
at System.Reflection.Emit.DynamicMethod..ctor(String name, Type
returnType, Type[] parameterTypes, Type owner, Boolean skipVisibility)
at Dapper.SqlMapper.CreateParamInfoGenerator(Identity identity,
Boolean checkForDuplicates, Boolean removeUnused, IList1 literals) in
D:\Dev\dapper-dot-net\Dapper NET40\SqlMapper.cs:line 3033 at
Dapper.SqlMapper.GetCacheInfo(Identity identity, Object
exampleParameters, Boolean addToCache) in D:\Dev\dapper-dot-net\Dapper
NET40\SqlMapper.cs:line 2138 at
Dapper.SqlMapper.<QueryImpl>d__611.MoveNext() in
D:\Dev\dapper-dot-net\Dapper NET40\SqlMapper.cs:line 1578 at
System.Collections.Generic.List1..ctor(IEnumerable1 collection)
at System.Linq.Enumerable.ToList[TSource](IEnumerable1 source) at
Dapper.SqlMapper.Query[T](IDbConnection cnn, String sql, Object param,
IDbTransaction transaction, Boolean buffered, Nullable1
commandTimeout, Nullable1 commandType) in
D:\Dev\dapper-dot-net\Dapper NET40\SqlMapper.cs:line 1479 at
Dapper.SqlMapper.Query(IDbConnection cnn, String sql, Object param,
IDbTransaction transaction, Boolean buffered, Nullable1
commandTimeout, Nullable1 commandType) in
D:\Dev\dapper-dot-net\Dapper NET40\SqlMapper.cs:line 1418 at
NinjaEvaluation.Data.Database.DapperWrapper.<>c__DisplayClass41.b__3(SqlConnection
sqlConnection, SqlTransaction transaction) in
c:\Projects\InHouse\ninjaevaluation\NinjaEvaluation\NinjaEvaluation.Data\Database\DapperWrapper.cs:line
52 at NinjaEvaluation.Data.Database.DapperWrapper.Invoke(Action`2
action) in
c:\Projects\InHouse\ninjaevaluation\NinjaEvaluation\NinjaEvaluation.Data\Database\DapperWrapper.cs:line
68
This happens in a completely normal situation when I run my query like this:
string sql = #" INSERT INTO XXX
(XXXId, AnotherId, ThirdId, Value, Comment)
VALUES
(#XXXId, #AnotherId, #ThirdId, #Value, #Comment)";
var parameters = command
.MyModels
.Select(model => new
{
XXXId= model.XXXId,
AnotherId= model.AnotherId,
ThirdId= model.ThirdId,
Value = model.Value,
Comment = model.Comment
})
.ToArray();
...
sqlConnection.Query(sql, parameters, commandType: commandType, transaction: transaction)
I found the following SO-thread started by someone having the same problem BUT the issue there seems to have been the .NET version (3.5) but I'm running .NET 4.5 and I can't figure out what the problem is.
Any suggestions?

I ran into this error when using an interface instead of the class:
Query<MyObject> worked, while Query<IMyObject> did not

It fails because this scenario using Query[<T>] isn't expecting an array / sequence of parameters. The Execute call-path does expect this, and unrolls the data automatically, executing the SQL once per item - but this isn't the case for Query[<T>], so it tries to create the dynamic method bound to the array (in your case), which isn't allowed. The code should probably detect this much earlier, and just say "nope, that isn't allowed".
You probably want to change your .ToArray() to .Single().
This will be clearer after the next build; the following passes:
public void SO30435185_InvalidTypeOwner()
{
try {
// not shown for brevity: something very similar to your code
Assert.Fail();
} catch(InvalidOperationException ex)
{
ex.Message.IsEqualTo("An enumerable sequence of parameters (arrays, lists, etc) is not allowed in this context");
}
}

LINQ to Entities does not recognize the method 'System.String StringConvert(System.Nullable`1[System.Double])

I can't figure out why I'm getting this error. I have used this function successfully with previous versions of Entity Framework but I've set up a new project using EF6 and it's not cooperating.
using System.Data;
using System.Data.Objects.SqlClient;
e.Result = from n in MyDB.tblBulletins
where n.AnncStart <= DateTime.Now && n.AnncEnd > DateTime.Now && n.Approved == true
orderby n.AnncStart descending, n.AnncDate descending
select new
{
n.RecID,
AnncTitle = n.AnncTitle + " <a href='bulletinAdd.aspx?ID=" + SqlFunctions.StringConvert((double)n.RecID).Trim() + "'><Edit></a>",
AnncText = (n.AnncImg == null ? n.AnncText : "<a href='images/bulletin/" + n.AnncImg + "'><img src='images/bulletin/" + n.AnncImg + "' class='stickyphoto' alt='Click for larger image'/></a>" + n.AnncText),
Email = (n.Email == null ? "" : "<br/><a href='mailto:" + n.Email + "'>" + n.Email + "</a>"),
n.AnncType,
n.AnncDate,
n.AnncEnd,
n.v_EmpBasicInfo.Name
};
When I run this I get
LINQ to Entities does not recognize the method 'System.String StringConvert(System.Nullable`1[System.Double])' method, and this method cannot be translated into a store expression.
n.RecID is an int primary key on the table in a SQL database (SQL Server Standard Edition)
All I can seem to find through searches is people recommending StringConvert instead of ToString
ADDITION - Stack Trace:
[NotSupportedException: LINQ to Entities does not recognize the method 'System.String StringConvert(System.Nullable`1[System.Double])' method, and this method cannot be translated into a store expression.]
System.Data.Entity.Core.Objects.ELinq.DefaultTranslator.Translate(ExpressionConverter parent, MethodCallExpression call) +194
System.Data.Entity.Core.Objects.ELinq.MethodCallTranslator.TypedTranslate(ExpressionConverter parent, MethodCallExpression linq) +976
System.Data.Entity.Core.Objects.ELinq.TypedTranslator`1.Translate(ExpressionConverter parent, Expression linq) +88
System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.TranslateExpression(Expression linq) +148
System.Data.Entity.Core.Objects.ELinq.BinaryTranslator.TypedTranslate(ExpressionConverter parent, BinaryExpression linq) +122
System.Data.Entity.Core.Objects.ELinq.TypedTranslator`1.Translate(ExpressionConverter parent, Expression linq) +88
System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.TranslateExpression(Expression linq) +148
System.Data.Entity.Core.Objects.ELinq.BinaryTranslator.TypedTranslate(ExpressionConverter parent, BinaryExpression linq) +87
System.Data.Entity.Core.Objects.ELinq.TypedTranslator`1.Translate(ExpressionConverter parent, Expression linq) +88
System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.TranslateExpression(Expression linq) +148
System.Data.Entity.Core.Objects.ELinq.NewTranslator.TypedTranslate(ExpressionConverter parent, NewExpression linq) +520
System.Data.Entity.Core.Objects.ELinq.TypedTranslator`1.Translate(ExpressionConverter parent, Expression linq) +88
System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.TranslateExpression(Expression linq) +148
System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.TranslateLambda(LambdaExpression lambda, DbExpression input) +168
System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.TranslateLambda(LambdaExpression lambda, DbExpression input, DbExpressionBinding& binding) +160
System.Data.Entity.Core.Objects.ELinq.OneLambdaTranslator.Translate(ExpressionConverter parent, MethodCallExpression call, DbExpression& source, DbExpressionBinding& sourceBinding, DbExpression& lambda) +168
System.Data.Entity.Core.Objects.ELinq.SelectTranslator.Translate(ExpressionConverter parent, MethodCallExpression call) +70
System.Data.Entity.Core.Objects.ELinq.SequenceMethodTranslator.Translate(ExpressionConverter parent, MethodCallExpression call, SequenceMethod sequenceMethod) +47
System.Data.Entity.Core.Objects.ELinq.MethodCallTranslator.TypedTranslate(ExpressionConverter parent, MethodCallExpression linq) +141
System.Data.Entity.Core.Objects.ELinq.TypedTranslator`1.Translate(ExpressionConverter parent, Expression linq) +88
System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.TranslateExpression(Expression linq) +148
System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.Convert() +50
System.Data.Entity.Core.Objects.ELinq.ELinqQueryState.GetExecutionPlan(Nullable`1 forMergeOption) +563
System.Data.Entity.Core.Objects.<>c__DisplayClassb.<GetResults>b__a() +83
System.Data.Entity.Core.Objects.ObjectContext.ExecuteInTransaction(Func`1 func, IDbExecutionStrategy executionStrategy, Boolean startLocalTransaction, Boolean releaseConnectionOnSuccess) +499
System.Data.Entity.Core.Objects.<>c__DisplayClassb.<GetResults>b__9() +271
System.Data.Entity.SqlServer.DefaultSqlExecutionStrategy.Execute(Func`1 operation) +251
System.Data.Entity.Core.Objects.ObjectQuery`1.GetResults(Nullable`1 forMergeOption) +600
System.Data.Entity.Core.Objects.ObjectQuery`1.<System.Collections.Generic.IEnumerable<T>.GetEnumerator>b__0() +89
System.Lazy`1.CreateValue() +416
System.Lazy`1.LazyInitValue() +152
System.Lazy`1.get_Value() +75
System.Data.Entity.Internal.LazyEnumerator`1.MoveNext() +40
System.Collections.Generic.List`1..ctor(IEnumerable`1 collection) +381
System.Linq.Enumerable.ToList(IEnumerable`1 source) +58
[TargetInvocationException: Exception has been thrown by the target of an invocation.]
System.RuntimeMethodHandle.InvokeMethod(Object target, Object[] arguments, Signature sig, Boolean constructor) +0
System.Reflection.RuntimeMethodInfo.UnsafeInvokeInternal(Object obj, Object[] parameters, Object[] arguments) +92
System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture) +108
System.Reflection.MethodBase.Invoke(Object obj, Object[] parameters) +19
System.Web.UI.WebControls.QueryableDataSourceHelper.ToList(IQueryable query, Type dataObjectType) +225
System.Web.UI.WebControls.LinqDataSourceView.ExecuteSelect(DataSourceSelectArguments arguments) +549
System.Web.UI.WebControls.Repeater.GetData() +55
System.Web.UI.WebControls.Repeater.CreateControlHierarchy(Boolean useDataSource) +89
System.Web.UI.WebControls.Repeater.OnDataBinding(EventArgs e) +61
System.Web.UI.WebControls.Repeater.DataBind() +105
System.Web.UI.WebControls.Repeater.EnsureDataBound() +49
System.Web.UI.WebControls.Repeater.OnPreRender(EventArgs e) +15
System.Web.UI.Control.PreRenderRecursiveInternal() +83
System.Web.UI.Control.PreRenderRecursiveInternal() +168
System.Web.UI.Control.PreRenderRecursiveInternal() +168
System.Web.UI.Control.PreRenderRecursiveInternal() +168
System.Web.UI.Control.PreRenderRecursiveInternal() +168
System.Web.UI.Control.PreRenderRecursiveInternal() +168
System.Web.UI.Control.PreRenderRecursiveInternal() +168
System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +974

I had the same problem and realized that I was using the wrong type of SqlFunctions. Make sure that you referenced the correct namespace:
using System.Data.Entity.SqlServer;
and not:
using System.Data.Objects.SqlClient;

You don't have to convert it to string, string concatenation will take care of that.
AnncTitle = n.AnncTitle + " <a href='bulletinAdd.aspx?ID=" + n.RecID + "'><Edit></a>",
You don't have to call ToString as well.

LINQ-NHibernate - Selecting only a few fields (including a Collection) for a complex object

I'm using Fluent NHibernate in one of my projects (and ASP.NET MVC application), with LINQ to query to data (using the LINQ to NHibernate libraries).
The objet names are changed to protect the innocent.
Let's say I have the following classes Foo, Bar, Baz, and their appropriate tables in the database (MySQL).
Foo has a many-to-many relationship with both Bar (table "FooBar") and Baz (table "FooBaz"), defined in the Fluent mappings. As such, the class interface is defined as follows:
public class Foo {
public virtual int id { get; set; }
public virtual string name { get; set; }
public virtual string email { get; set; }
public virtual IList<Bar> bars { get; set; }
public virtual IList<Baz> bazes { get; set; }
}
This is a pretty standard class. We can see that a Foo object will have a list of bars and bazes.
The problem comes when trying to do a LINQ query.
If I do a simple query like this, it works fine (the where clause is unimportant) :
var foos = from foo in session.Linq<Foo>()
where email.equals("foo#bar.com")
select foo;
IList<Foo> listFoos = foos.ToList();
This will return a list of Foos, with all the fields populated (id, name, email, bars, bazes). log4net shows that NHibernate performs separate queries for the collections.
The problem arises when I want to load only some fields. For example, I might want to load only the bars in the query, but not the bazes.
This query compiles, but produces an error at runtime:
var foos = from foo in session.Linq<Foo>()
where email.equals("foo#bar.com")
select new Foo()
{
id = foo.id,
name = foo.name,
email = foo.email,
bars = foo.bars
};
IList<Foo> listFoos = foos.ToList();
The error I get is something along the lines of an array index out of bounds exception. The stack trace shows some methods names relating the collection handling on LINQ-NHibernate's side, but nothing else. The query reported by log4net shows no sign of a query on bars, which means than an error was caught before it had the time to perform the query to select the bars.
Did anyone else had this kind of problem before? How did you solve it? I don't want to have to select all the objects everytime I open a web page in my application!
Thank you!
Edit: here is the stacktrace, as requested.
System.IndexOutOfRangeException: L'index se trouve en dehors des limites du tableau. (read: "Index is out of bounds for the array.")
[IndexOutOfRangeException: L'index se trouve en dehors des limites du tableau.]
NHibernate.Transform.TypeSafeConstructorMemberInitResultTransformer.InvokeMemberInitExpression(MemberInitExpression expression, Object[] args, Int32& argumentCount) +404
NHibernate.Transform.TypeSafeConstructorMemberInitResultTransformer.TransformTuple(Object[] tuple, String[] aliases) +150
[QueryException: could not instantiate: Foo]
NHibernate.Transform.TypeSafeConstructorMemberInitResultTransformer.TransformTuple(Object[] tuple, String[] aliases) +265
NHibernate.Loader.Criteria.CriteriaLoader.GetResultColumnOrRow(Object[] row, IResultTransformer resultTransformer, IDataReader rs, ISessionImplementor session) +171
NHibernate.Loader.Loader.GetRowFromResultSet(IDataReader resultSet, ISessionImplementor session, QueryParameters queryParameters, LockMode[] lockModeArray, EntityKey optionalObjectKey, IList hydratedObjects, EntityKey[] keys, Boolean returnProxies) +330
NHibernate.Loader.Loader.DoQuery(ISessionImplementor session, QueryParameters queryParameters, Boolean returnProxies) +704
NHibernate.Loader.Loader.DoQueryAndInitializeNonLazyCollections(ISessionImplementor session, QueryParameters queryParameters, Boolean returnProxies) +70
NHibernate.Loader.Loader.DoList(ISessionImplementor session, QueryParameters queryParameters) +111
NHibernate.Loader.Loader.ListIgnoreQueryCache(ISessionImplementor session, QueryParameters queryParameters) +18
NHibernate.Loader.Loader.List(ISessionImplementor session, QueryParameters queryParameters, ISet`1 querySpaces, IType[] resultTypes) +79
NHibernate.Impl.SessionImpl.List(CriteriaImpl criteria, IList results) +407
NHibernate.Impl.CriteriaImpl.List(IList results) +41
NHibernate.Impl.CriteriaImpl.List() +35
NHibernate.Linq.<GetEnumerator>d__0.MoveNext() +71
System.Collections.Generic.List`1..ctor(IEnumerable`1 collection) +7665172
System.Linq.Enumerable.ToList(IEnumerable`1 source) +61
FooRepository.List(Int32 count) in C:\...\FooRepository.cs:38
FooController.List() in C:\...\FooController.cs:30
lambda_method(ExecutionScope , ControllerBase , Object[] ) +39
System.Web.Mvc.ActionMethodDispatcher.Execute(ControllerBase controller, Object[] parameters) +17
System.Web.Mvc.ReflectedActionDescriptor.Execute(ControllerContext controllerContext, IDictionary`2 parameters) +178
System.Web.Mvc.ControllerActionInvoker.InvokeActionMethod(ControllerContext controllerContext, ActionDescriptor actionDescriptor, IDictionary`2 parameters) +24
System.Web.Mvc.<>c__DisplayClassa.<InvokeActionMethodWithFilters>b__7() +52
System.Web.Mvc.ControllerActionInvoker.InvokeActionMethodFilter(IActionFilter filter, ActionExecutingContext preContext, Func`1 continuation) +254
System.Web.Mvc.<>c__DisplayClassc.<InvokeActionMethodWithFilters>b__9() +19
System.Web.Mvc.ControllerActionInvoker.InvokeActionMethodWithFilters(ControllerContext controllerContext, IList`1 filters, ActionDescriptor actionDescriptor, IDictionary`2 parameters) +192
System.Web.Mvc.ControllerActionInvoker.InvokeAction(ControllerContext controllerContext, String actionName) +399
System.Web.Mvc.Controller.ExecuteCore() +126
System.Web.Mvc.ControllerBase.Execute(RequestContext requestContext) +27
System.Web.Mvc.ControllerBase.System.Web.Mvc.IController.Execute(RequestContext requestContext) +7
System.Web.Mvc.MvcHandler.ProcessRequest(HttpContextBase httpContext) +151
System.Web.Mvc.MvcHandler.ProcessRequest(HttpContext httpContext) +57
System.Web.Mvc.MvcHandler.System.Web.IHttpHandler.ProcessRequest(HttpContext httpContext) +7
System.Web.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +181
System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +75

A couple of suggestions...
First, NHibernate defaults to lazy loading, so there may not even be a need to do the more "efficient" query you're attempting.
Second, the following code does not quite do what your example code does - it creates a list of anonymous types called miniFoos that contain a subset of the fields in Foo. But the net effect is similar to what you seem to be attempting. It also uses what I believe is called LINQ method syntax.
I tested this in on an entity in my own application, which also has an IList property, and it does work (though I should note that I'm currently using Eager loading). I just cut and pasted the working code and substituted your example's names.
using( var session = sessionFactory.OpenSession() )
{
session.BeginTransaction();
var foos =
session.CreateCriteria(typeof(Foo))
.List<Foo>();
var miniFoos =
foos.Select(f => new { f.email, f.bars })
.Where(f => f.email.Equals("foo#bar.com)
.ToList();
session.Close();
}

I tried answering this already, but am not happy with it.
The more I think about your question, the more it seems like you are trying to do your own version of Lazy Loading, which NHibernate handles pretty well on it's own, in my experience.
I know (from a comment) that you switched to Eager Loading because you were not keeping a session open. I think it would be more useful for you in the long run if you focused on that angle.
If I've misunderstood, perhaps you could edit the question to explain why you think you need to handle it yourself?

I could manage to project not the whole collection but its fields
...
Select(a => new Forum {
Id = a.Id,
Name = a.Name,
CategoryName = a.Categories.Select(b => b.Name).First()
})
CategoryName is an computed filed in the Forum Entity
which does not have any mapping with DB
In result I got a small projection of the huge Forum Entity and a possibility to sort on the field.
Hope that it will help somebody.

i think you can solve your problem by defining the result transformer and the result set names, if in some way you can access the Criteria that being generated you can avoid anonymous object.
the problem is that the property names and column names are not the same, and when using projection nhibernate/linq to nhibernate does not check what the column name and the property name. so if u'll define them by yourself in the result properties (i think its called result set) in the criteria before you execute the query it should work.
it's pretty simple, give it a try