Querying a specific set of data properties (more than one)

[un-tone]

Currently is supported the Select method only for single properties, e.g.:

DbLinq.Objects<Person>().Select(x => x.Name);

SELECT p.Name FROM Person p

More complex queries, like:

DbLinq.Objects<Person>().Select(x => new {x.Name, x.Age});
DbLinq.Objects<Person>().Select(x => new Tuple<string, uint>(x.Name, x.Age));

SELECT p.Name, p.Age FROM Person p

don't work.

[PatrykSzwer]

I just tried Select like this in BlendingEditor code and its also not working correctly:

            this.LayoutThemeConfigurations.Data = DbLinq.Objects<CssCollectionRelation>()
                .Where(x => x.Template == this.Data).Select(x => x.Collection);

error:

PalindromConnectionError: Server error
	System.Exception: ScErrQueryResultTypeMismatch (SCERR7031): Expected generic result type does not match with query result type. The result type BlendingEditor.DataModels.CssCollectionRelation cannot be assigned from the query result, which is of type BlendingEditor.DataModels.CssCollection.
	Version: 2.4.990.183.
	Help page: https://docs.starcounter.io/?q=SCERR7031.
	   at Starcounter.Query.QueryPreparation.MatchEnumeratorResultAndExpectedType[T](IExecutionEnumerator execEnum)
	   at Starcounter.Query.QueryPreparation.PrepareOrExecuteQuery[T](String appName, String query, Boolean slowSql, Object[] values)
	   at Starcounter.Query.Sql.SqlEnumCache.CacheOrExecuteEnumerator[T](String appName, String query, Boolean slowSQL, Object[] values)
	   at Starcounter.QueryProcessor.Db.FullQueryProcess[T](String query, Boolean slowSQL, String appName, Object[] values)
	   at Starcounter.Db.FullQueryProcess[T](String query, Boolean slowSQL, String appName, Object[] values) in C:\tc_work\sc-19632\Level1\src\Starcounter\Mock\Db.cs:line 133
	   at Starcounter.Db.SlowSQL[T](String query, Object[] values) in C:\tc_work\sc-19632\Level1\src\Starcounter\Mock\Db.cs:line 121
	   at Starcounter.Linq.QueryExecutor`1.Execute[TResult](String sql, Object[] variables, QueryResultMethod queryResultMethod)
	   at Starcounter.Linq.QueryProvider.System.Linq.IQueryProvider.Execute[T](Expression expression)
	   at Starcounter.Linq.Queryable`1.System.Collections.IEnumerable.GetEnumerator()
	   at Starcounter.Json.Array_InitializeAfterImplicitConversion(Json parent, TObjArr template) in c:\Git\Starcounter.XSON\src\Starcounter.XSON\Class Json\Json.Array.cs:line 84
	   at Starcounter.Transaction.Scope(Action action) in C:\tc_work\sc-19632\Level1\src\Starcounter\Transaction.cs:line 225
	   at Starcounter.XSON.Internal.XSONInternals.RunWithinApplication(String appName, Action action) in c:\Git\Starcounter.XSON\src\Starcounter.XSON\Internal\XSONInternals.cs:line 41
	   at BlendingEditor.Website.ViewModels.GeneralPage.Handle(SaveModalTrigger action) in C:\Repositories\HeadsOmni\src\Blending.Mapper\Blending\src\BlendingEditor\Website\ViewModels\GeneralPage.json.cs:line 175
	   at BlendingEditor.Website.ViewModels.GeneralPage.JsonByExample.Schema.<>c.<.ctor>b__0_31(Json pup, Input`1 input)
	   at Starcounter.XSON.Internal.XSONInternals.RunWithinApplication(String appName, Action action) in c:\Git\Starcounter.XSON\src\Starcounter.XSON\Internal\XSONInternals.cs:line 41
	   at Starcounter.Templates.Property`1.ProcessInput(Json parent, T newValue) in c:\Git\Starcounter.XSON\src\Starcounter.XSON\Templates\Foundation\Property.cs:line 340
	   at Starcounter.XSON.JsonPatch.DefaultPatchHandler.ParseAndProcess(TLong property, Json parent, String valueStr) in c:\Git\Starcounter.XSON\src\Starcounter.XSON\Sessions\JSON-Patch\DefaultPatchHandler.cs:line 149
	   at Starcounter.Internal.TransactionManager.Scope(TransactionHandle handle, Action action) in C:\tc_work\sc-19632\Level1\src\Starcounter\TransactionManager.cs:line 557
	   at Starcounter.Transaction.Scope(Action action) in C:\tc_work\sc-19632\Level1\src\Starcounter\Transaction.cs:line 233
	   at Starcounter.XSON.Internal.XSONInternals.RunWithinApplication(String appName, Action action) in c:\Git\Starcounter.XSON\src\Starcounter.XSON\Internal\XSONInternals.cs:line 41
	   at Starcounter.XSON.JsonPatch.DefaultPatchHandler.Handle(Json root, JsonPatchOperation patchOp, JsonPointer pointer, String value) in c:\Git\Starcounter.XSON\src\Starcounter.XSON\Sessions\JSON-Patch\DefaultPatchHandler.cs:line 38
	   at Starcounter.XSON.JsonPatch.JsonPatch.HandleOnePatch(Json root, JsonPatchOperation op, JsonPointer ptr, String value, Int32 patchCount, ChangeLog changeLog, Object sourceJson, Boolean strictRejection, JsonPatchStatus previousStatus) in c:\Git\Starcounter.XSON\src\Starcounter.XSON\Sessions\JSON-Patch\JsonPatch.cs:line 467

[un-tone]

@PatrykSzwer such an issue is for #46. This one is exactly for set of properties (more than one), like .Select(x => new {x.Name, x.Age}).

Also I can't reproduce the bug in SC 2.4.991 and 2.4.0.6930.
Can I ask you to isolate the case so it can be easy reproduced? And please describe it in the #46, not here.

[PatrykSzwer]

Also I can't reproduce the bug in SC 2.4.991 and 2.4.0.6930.

I tested it in 990.183 When we update to higher version and problem will still occur then I'll let you know.

[un-tone]

Started this issue in the select-multi-target branch.