如何从 guid null 中使系统为空值？

Question

在构建查询中，我有一个这样的查询：

var characteristicPrices = await scope.BuildQuery<CharacteristicPrice, CharacteristicVersion, CharacteristicPrice>((op, ccp, cv) => op.Select(op.AllColumnsOf(ccp))
   .InnerJoin<CharacteristicVersion>(cv.Id == ccp.CharacteristicVersionId)
   .Where(ccp.CountryId == request.CountryId && cv.VersionId == request.VersionId)).Get();

这里的 request.CountryId 字段对我来说是“000000...”。但我的查询无法正常工作，因为它的等效项在数据库中为空。如何将此值设置为空？

Answer 1

您可以直接将 null 传递给查询而不是 Guid.Empty，或者您可以修改您的条件：

要么……

Guid? id = request.CountryId;
if (id==Guid.Empty) 
{ 
  id = null; 
}
var characteristicPrices = await scope.BuildQuery<CharacteristicPrice, CharacteristicVersion, CharacteristicPrice>((op, ccp, cv) => op.Select(op.AllColumnsOf(ccp))
   .InnerJoin<CharacteristicVersion>(cv.Id == ccp.CharacteristicVersionId)
   .Where(ccp.CountryId == id && cv.VersionId == request.VersionId)).Get();

...或者...

var characteristicPrices = await scope.BuildQuery<CharacteristicPrice, CharacteristicVersion, CharacteristicPrice>((op, ccp, cv) => op.Select(op.AllColumnsOf(ccp))
   .InnerJoin<CharacteristicVersion>(cv.Id == ccp.CharacteristicVersionId)
   .Where((ccp.CountryId == request.CountryId || (request.CountryId==Guid.Empty && ccp.CountryId=null)) && cv.VersionId == request.VersionId)).Get();

如何从 guid null 中使系统为空值？

How can I make the system empty value from the guid null?

c#

guid