Linq到SQL:使用int?作为查询中的参数

我以前也有过这个问题。我找到的解决办法是:

public IQueryable<Clam> getAllClams(int clamTypeID, int? parentClamID)
{
     return from clam in Clams
            where clam.ClamTypeID == clamTypeID &&
                  object.Equals(clam.ParentClamID, parentClamID)
            select clam;
}

public IQueryable<Clam> getAllClams(int clamTypeID, int? parentClamID)
{
     return from clam in Clams
            where clam.ClamTypeID == clamTypeID &&
                  clam.ParentClamID == parentClamID.HasValue ? parentClamID.Value : null 
            select clam;
}

试试这个:

public IQueryable<Clam> getAllClams(int clamTypeID, int? parentClamID)
{
     var result = from clam in Clams where clam.ClamTypeID == clamTypeID select clam;

      if(parentClamID.HasValue) result = result.Where(c => c.ParentClamID == parentClamID);
      else result = result.Where(c => c.ParentClamID == null);

      return from clam in result select clam;
}