Home / Questions / 50572
Accepted
German AT
Asked: 2020-02-21 11:13:09 +0800 CST 2020-02-21 11:13:09 +0800 CST

how to structure a query using union with composite key

  • 772

I am trying to make a join between tables using linq where the key that joins them must be composed of two fields

var devengados = (from inten in ctx.INTENCIONES
                  join contr in ctx.CONTRATOS on inten.intencion_id equals contr.intencion_id
                  join intFin in ctx.INTENCIONES_FINANCIAMIENTO on new { inten.intencion_id, inten.orden } equals new { intFin.intencion_id, intFin.orden }
                  where contr.contrato_id == iContratoId
                  select new { inten, contr, intFin }).First();

With this structure I have an error in the join of intFin:

Error 31 The type of one of the expressions in the join clause is incorrect. Type inference failed in the call to 'Join'.

c#

1 Answers

  1. Best Answer

    Make sure the types and names of the properties you are comparing match. Try the following:

    new { p1 = inten.intencion_id, p2 = inten.orden } equals new { p1 = intFin.intencion_id, p2 = intFin.orden }

    If you have different data types, try to do the necessary conversions, like the following:

    new { p1 = inten.intencion_id, p2 = (int)inten.orden } equals new { p1 = intFin.intencion_id, p2 = intFin.orden }

    Also make sure you're not comparing one property nulleableto another with isn't, if this is the case you can also do a conversion like the following:

    new { p1 = inten.intencion_id, p2 = (int?)inten.orden } equals new { p1 = intFin.intencion_id, p2 = intFin.orden }
    • 1