两个dbcontexts导致错误“值不能为空。参数名称实体类型”

Question

我的应用程序中有2个DbContext，需要在2个表中进行联接，每个表在不同的DbContext中；我收到此错误

  

value不能为null。参数名称实体类型

当我尝试联接具有相同上下文的2个表时，不会发生此错误。

var VerificaExistenciaSinistro = sinistroContext.SnsAviso
  .Join(
    sinistroContext.SnsNumAviso, 
    sinistro => sinistro.NumApo,
    aviso    => aviso.NumApo,
    (sinistro, aviso) => new { 
      sinistroV = sinistro, 
      avisoV = aviso })
  .Where(c => c.sinistroV.CodItm == c.avisoV.CodItm &&
    c.sinistroV.NumApo == c.avisoV.NumApo && 
    c.sinistroV.NumAvs == c.avisoV.SeqNumAvs)
  .Join(sgsContext.EmsEmissao,
    sinistro1 => sinistro1.sinistroV.CodCtrtAvs,
    emissao   => emissao.CodCtrt,
    (sinistro1, emissao) => new { 
      sinistroC = sinistro1, 
      emissaoC = emissao })
  .Where(c => c.sinistroC.sinistroV.CodCtrtAvs == c.emissaoC.CodCtrt && 
    c.emissaoC.CodEmis == c.sinistroC.avisoV.CodEms)
  .Where(x => x.sinistroC.sinistroV.NumApo == apolice &&
    x.emissaoC.StsEmis == emissao && 
    x.emissaoC.NumEndosso ==endosso && 
    x.sinistroC.sinistroV.CodItm == cod_itm && 
    x.sinistroC.sinistroV.CodCbe == cbeCod)
  .Select(x => x.sinistroC)
  .ToList();