Question

With regards to this question here SQL CLR return two new columns I am trying to create a simple SQL CLR function, where I can pass two strings into the function and it passes me back two NEW columns.

So say I have the following data:-

Col A     Col B
Bob       Joe
Jane      John

I want to be able to pass Col A and Col B to a CLR function and have it return something like this (whereby Col C and D are new columns):-

Col A     Col B     Col C     Col D
Bob       Joe       BobCLR    JoeCLR
Jane      John      JaneCLR   JohnCLR

I have the following code:-

 [SqlFunction(FillRowMethodName = "FillRow")]
    public static IEnumerable MyCLRFunction(string A, string B)
    {
        String[] values = new String[2];
        values[0] = A+"CLR";
        values[1]= B+"CLR";

        return values;
    }

         private static void FillRow(Object obj, out string C, out string D)
      {
            String[] row = (object[])obj;
            C = (string)row[0];
            D = (string)row[1];
      }

I can register the assembly in SQL Server ok using CREATE ASSEMBLY

I can create the function ok in SQL Server as follows:-

CREATE FUNCTION dbo.MyCLRFunction(@a [nvarchar](4000), @b [nvarchar](4000))
RETURNS TABLE
(c [nvarchar](4000) null, d [nvarchar](4000) null) with execute as caller
AS
EXTERNAL NAME [MyNamespace].[CLRFunctions].[MyCLRFunction]

However when I do:-

SELECT * FROM MyCLRFunction('Bob','Joe')

Im getting:-

Msg 6260, Level 16, State 1, Line 1
An error occurred while getting new row from user defined Table Valued Function : 
System.InvalidCastException: Unable to cast object of type 'System.String' to type 'System.String[]'.
System.InvalidCastException: 
   at CLRFunctions.FillRow(Object obj, String& C, String& D)

Answer 1

Ok have managed to do this now using a KeyValuePair within an Ienumerable.

using System;
using System.Collections;
using System.Collections.Generic;
using System.Data.SqlTypes;
using Microsoft.SqlServer.Server;

public class CLRFunctions
{

    private static IEnumerable<KeyValuePair<double, double>> CoordinatesEnumerable(double Lat, double Long)
    {
        return new Dictionary<double, double> { { Lat, Long } };
    }

    [SqlFunction(FillRowMethodName = "FillRow")]
    public static IEnumerable ToLatLong(double East, double North)
    {
        return CoordinatesEnumerable(East, North);
    }

    private static void FillRow(Object obj, out SqlDouble Lat, out SqlDouble Long)
    {
        KeyValuePair<double, double> Coordinates = (KeyValuePair<double, double>)obj;
        Lat = new SqlDouble(Coordinates.Key);
        Long = new SqlDouble(Coordinates.Value);
    }

}