Convert SQL query to linq with union

Question

I have the following SQL query:

SELECT
    a.DocumentNumber, a.ItemNumber, 
    SUM(a.ItemAmount) AS ItemAmount 
FROM
    (SELECT
         SopNumbe AS DocumentNumber, ITEMNMBR AS ItemNumber, 
         XTNDPRCE AS ItemAmount
     FROM
         dbo.SOP30300 
     WHERE
         SOPNUMBE = '8403017              ' 
         AND XTNDPRCE <> 0
     UNION ALL
     SELECT 
         LAPTODNM AS DocumentNumber, LITMNMBR AS ItemNumber, 
         -1 * ta.APPTOAMT AS ItemAmount 
     FROM
         dbo.RM20201 a 
     LEFT JOIN
         dbo.TRM20201 ta ON a.APFRDCNM = ta.LAPFRDNM 
                         AND a.APTODCNM = ta.LAPTODNM 
     WHERE
         ta.LAPTODNM = '8403017              ') a
GROUO BY
    a.DocumentNumber, a.ItemNumber 
HAVING
    SUM(a.ItemAmount) > 0

Here is the linq I am trying

var result = (from sop in _librgContext.Sop30300
              where sop.Sopnumbe == "8403017" && sop.Xtndprce != 0
              select new InvoiceSummary
              {
                  DocumentNumber = sop.Sopnumbe,
                  ItemNumber = sop.Itemnmbr,
                  ItemAmount = sop.Xtndprce
              })
  .Union(
  from rm in _librgContext.Rm20201
  join ta in _librgContext.TRM20201 on new { Key1 = rm.ApplyFromDocumentNumber, Key2 = rm.ApplyToDocumentNumber } equals new { Key1 = ta.Lapfrdnm, Key2 = ta.Laptodnm } into joinResult
  from ta in joinResult.DefaultIfEmpty()
  where ta != null && ta.Laptodnm == "8403017" // Added null check for ta
                                               // && rm.GLPOSTDT <= CutoffDate // Uncomment if @CutoffDate is a parameter
  select new InvoiceSummary
  {
      DocumentNumber = ta.Laptodnm, // Adjusted to use LAPTODNM from ta
      ItemNumber = ta.Litmnmbr,
      ItemAmount = -1 * (ta != null ? rm.ApplyToAmount : 0)
  })
  .GroupBy(a => new { a.DocumentNumber, a.ItemNumber })
  .Where(g => g.Sum(a => a.ItemAmount) > 0)
  .Select(g => new InvoiceSummary
  {
      DocumentNumber = g.Key.DocumentNumber,
      ItemNumber = g.Key.ItemNumber,
      ItemAmount = g.Sum(a => a.ItemAmount)
  });   

Got the following on debugging Unable to translate set operation when matching columns on both sides have different store types.

Answer 1

Ok finally I am able to do this which is working as expected as of now

var result1 = (
from sop in _librgContext.Sop30300
where sop.Sopnumbe == sopNumber && sop.Xtndprce != 0
select new InvoiceSummary
{
  DocumentNumber = sop.Sopnumbe,
  ItemNumber = sop.Itemnmbr,
  ItemAmount = sop.Xtndprce
}).ToList(); // Execute the query to bring the data into memory

    var result2 = (
        from rm in _librgContext.Rm20201
        join ta in _librgContext.TRM20201
        on new
        {
            rm.ApplyFromDocumentNumber,
             rm.ApplyToDocumentNumber
        } equals new
        {
            ApplyFromDocumentNumber = ta.Lapfrdnm,
            ApplyToDocumentNumber = ta.Laptodnm
        } into joinResult
        from ta in joinResult.DefaultIfEmpty()
        where ta != null && ta.Laptodnm == sopNumber
        select new InvoiceSummary
        {
            DocumentNumber = ta.Laptodnm, // Removed ToString() conversion
            ItemNumber = ta.Litmnmbr, // Removed ToString() conversion
            ItemAmount = -1 * (ta != null ? rm.ApplyToAmount : 0)
        }).ToList(); // Execute the query to bring the data into memory

    var combinedResult = result1.Concat(result2)
        .GroupBy(a => new { a.DocumentNumber, a.ItemNumber })
        .Where(g => g.Sum(a => a.ItemAmount) > 0)
        .Select(g => new InvoiceSummary
        {
            DocumentNumber = g.Key.DocumentNumber,
            ItemNumber = g.Key.ItemNumber,
            ItemAmount = g.Sum(a => a.ItemAmount)
        });

    var finalResult = combinedResult.ToList();