how to use CreateAggregate for sum operator sqlite

Question

Hi,

I get this error that SQLite cannot apply aggregate operator 'Sum' on expressions of type 'decimal'. Convert the values to a supported type, or use LINQ to Objects to aggregate the results on the client side.

I searhed it. I think it can be override using sqlitefunction. Cold you help about it. I found some example from Microsoft Learn

https://learn.microsoft.com/tr-tr/dotnet/standard/data/sqlite/user-defined-functions

But there is no example about SUM operator

 connection.CreateFunction(  
     "volume",  
     (double radius, double height)  
         => Math.PI * Math.Pow(radius, 2) * height);  

and this example exists

 connection.CreateFunction(  
     "regexp",  
     (string pattern, string input)  
         => Regex.IsMatch(input, pattern));  

and this example exists

connection.CreateAggregate(  
     "stdev",  
      
     // A tuple to maintain context between rows  
     (Count: 0, Sum: 0.0, SumOfSquares: 0.0),  
      
     // This is called for each row  
     ((int Count, double Sum, double SumOfSquares) context, double value) =>  
     {  
         context.Count++;  
         context.Sum += value;  
         context.SumOfSquares += value * value;  
      
         return context;  
     },  
      
     // This is called to get the final result  
     context =>  
     {  
         var variance = context.SumOfSquares - context.Sum * context.Sum / context.Count;  
      
         return Math.Sqrt(variance / context.Count);  
     });  

Is it possible to write something like this for the sum operator? how ?

=======================================

[SqliteFunctionAttribute(Name = "SUM", Arguments = 1, FuncType = FunctionType.Aggregate)]  
     class SqliteSum : SqliteFunction {  
         public override void Step(object[] args, int stepNumber, ref object contextData) {  
             if (args.Length < 1 || args[0] == null || args[0] == DBNull.Value)  
                 return;  
             try {  
                 decimal d = Math.Round(Convert.ToDecimal(args[0]), 4);  
                 if (contextData != null) d += (Decimal)contextData;  
                 contextData = d;  
             } catch (Exception ex) {  
                 WebServer.Log("Exception: {0}", ex);  
             }  
         }  
      
         public override object Final(object contextData) {  
             return contextData;  
         }  
     }  

Answer 1

I don't believe mapping aggregate functions by attribute was ever implemented (it uses a different registering method). you should use the new syntax.