GroupBy - not supported exception

Given such a LINQ query

IQueryable<GFDDataModels.Stone> stones;
stones = from s in _dataContext.Stone where s.Enabled == true select s;

stones = from s in stones
              where !s.Name.StartsWith("level - ") && s.ImageFullUrl.Length > 0
              group s by s.Name
              into sG
              select sG.First();

var list = stones.ToList();

it fails with the exception. "The method or operation is not implemented."

Stack Trace:

   at LinqToDB.Linq.Builder.GroupByBuilder.GroupByContext.ConvertToSql(Expression expression, Int32 level, ConvertFlags flags) in c:\projects\linq2db\Source\Linq\Builder\GroupByBuilder.cs:line 520
   at LinqToDB.Linq.Builder.SelectContext.<>c__DisplayClass21.<ConvertToSql>b__13(IBuildContext ctx, Expression ex, Int32 l) in c:\projects\linq2db\Source\Linq\Builder\SelectContext.cs:line 284
   at LinqToDB.Linq.Builder.SelectContext.ProcessScalar[T](Expression expression, Int32 level, Func`4 action, Func`1 defaultAction) in c:\projects\linq2db\Source\Linq\Builder\SelectContext.cs:line 890
   at LinqToDB.Linq.Builder.SelectContext.ConvertToSql(Expression expression, Int32 level, ConvertFlags flags) in c:\projects\linq2db\Source\Linq\Builder\SelectContext.cs:line 281
   at LinqToDB.Linq.Builder.SelectContext.<>c__DisplayClass21.<ConvertToSql>b__13(IBuildContext ctx, Expression ex, Int32 l) in c:\projects\linq2db\Source\Linq\Builder\SelectContext.cs:line 284
   at LinqToDB.Linq.Builder.SelectContext.ProcessScalar[T](Expression expression, Int32 level, Func`4 action, Func`1 defaultAction) in c:\projects\linq2db\Source\Linq\Builder\SelectContext.cs:line 917
   at LinqToDB.Linq.Builder.SelectContext.ConvertToSql(Expression expression, Int32 level, ConvertFlags flags) in c:\projects\linq2db\Source\Linq\Builder\SelectContext.cs:line 281
   at LinqToDB.Linq.Builder.ExpressionContext.ConvertToSql(Expression expression, Int32 level, ConvertFlags flags) in c:\projects\linq2db\Source\Linq\Builder\ExpressionContext.cs:line 48
   at LinqToDB.Linq.Builder.ExpressionBuilder.ConvertToSql(IBuildContext context, Expression expression, Boolean unwrap) in c:\projects\linq2db\Source\Linq\Builder\ExpressionBuilder.SqlBuilder.cs:line 823
   at LinqToDB.Linq.Builder.ExpressionBuilder.ConvertExpressions(IBuildContext context, Expression expression, ConvertFlags queryConvertFlag) in c:\projects\linq2db\Source\Linq\Builder\ExpressionBuilder.SqlBuilder.cs:line 619
   at LinqToDB.Linq.Builder.OrderByBuilder.BuildMethodCall(ExpressionBuilder builder, MethodCallExpression methodCall, BuildInfo buildInfo) in c:\projects\linq2db\Source\Linq\Builder\OrderByBuilder.cs:line 49
   at LinqToDB.Linq.Builder.MethodCallBuilder.BuildSequence(ExpressionBuilder builder, BuildInfo buildInfo) in c:\projects\linq2db\Source\Linq\Builder\MethodCallBuilder.cs:line 22
   at LinqToDB.Linq.Builder.ExpressionBuilder.BuildSequence(BuildInfo buildInfo) in c:\projects\linq2db\Source\Linq\Builder\ExpressionBuilder.cs:line 177
   at LinqToDB.Linq.Builder.CountBuilder.BuildMethodCall(ExpressionBuilder builder, MethodCallExpression methodCall, BuildInfo buildInfo) in c:\projects\linq2db\Source\Linq\Builder\CountBuilder.cs:line 21
   at LinqToDB.Linq.Builder.MethodCallBuilder.BuildSequence(ExpressionBuilder builder, BuildInfo buildInfo) in c:\projects\linq2db\Source\Linq\Builder\MethodCallBuilder.cs:line 22
   at LinqToDB.Linq.Builder.ExpressionBuilder.BuildSequence(BuildInfo buildInfo) in c:\projects\linq2db\Source\Linq\Builder\ExpressionBuilder.cs:line 177
   at LinqToDB.Linq.Builder.ExpressionBuilder.Build[T]() in c:\projects\linq2db\Source\Linq\Builder\ExpressionBuilder.cs:line 148
   at LinqToDB.Linq.Query`1.GetQuery(IDataContextInfo dataContextInfo, Expression expr) in c:\projects\linq2db\Source\Linq\Query.cs:line 165
   at LinqToDB.Linq.ExpressionQuery`1.GetQuery(Expression expression, Boolean cache) in c:\projects\linq2db\Source\Linq\ExpressionQuery.cs:line 89
   at LinqToDB.Linq.ExpressionQuery`1.System.Linq.IQueryProvider.Execute[TResult](Expression expression) in c:\projects\linq2db\Source\Linq\ExpressionQuery.cs:line 142
   at System.Linq.Queryable.Count[TSource](IQueryable`1 source)
   at GFD.DB.BL.Stone.GetMaterial(Int32 fabricatorId, String name, String tag, Int32 page, Int32 perPage) in D:\QuoteGranite\src\Main\gfd\GFD.DB\BL\Stone.BL.cs:line 105
   at gfd.Controllers.Api.QuoteCountertopsController.<>c__DisplayClass4_0.<GetMaterial>b__0(GFDDataContext context, AuthModel auth, IDependencyResolver depRes) in D:\QuoteGranite\src\Main\gfd\gfd\Controllers\Api\QuoteCountertopsController.cs:line 87
   at gfd.Controllers.Api.BaseApiController.Do(Func`4 a) in D:\QuoteGranite\src\Main\gfd\gfd\Controllers\Api\BaseApiController.cs:line 146

[integral-llc]

Here it is. I’ve also tried in LinqPad with latest Linq2Db driver and got the same issue.

	[Table(Schema="dbo", Name="Stone")]
	public partial class Stone
	{
		[PrimaryKey, Identity   ] public int             Id              { get; set; } // int
		[Column,     NotNull    ] public string          Name            { get; set; } // nvarchar(256)
		[Column,        Nullable] public bool?           Enabled         { get; set; } // bit
		[Column,        Nullable] public DateTimeOffset? Created         { get; set; } // datetimeoffset(7)
		[Column,        Nullable] public DateTimeOffset? Modified        { get; set; } // datetimeoffset(7)
		[Column,        Nullable] public int?            CreatedBy_id    { get; set; } // int
		[Column,        Nullable] public int?            ModifiedBy_id   { get; set; } // int
		[Column,        Nullable] public string          Tags            { get; set; } // nvarchar(512)
		[Column,        Nullable] public string          Description     { get; set; } // nvarchar(512)
		[Column,        Nullable] public string          ImageUrl        { get; set; } // nvarchar(255)
		[Column,        Nullable] public string          ImageFullUrl    { get; set; } // nvarchar(255)
		[Column,        Nullable] public string          Aliases         { get; set; } // nvarchar(1024)
		[Column,        Nullable] public string          LongDescription { get; set; } // nvarchar(2048)
}

[MaceWindu]

I’m going to close it, as original issue fixed, and requirement to set GuardGrouping = false is valid with current implementation