Question

我可能正在使用错误的方法来发起查询。这是带有Sql Server后端的EF6。我有：

class Client(Model):
    name = CharField(max_length=50)
    email = EmailField(max_length=100, verbose_name="E-mail")
    title = CharField(max_length=50)
    department = CharField(max_length=50)

    def get_string_fields(self):
        # list of some excluded fields
        excluded_fields = ['id', 'pk']

        # getting all fields that available in `Client` model,
        # but not in `excluded_fields`
        field_names = [field.name for field in Client._meta.get_fields() 
                       if field.name not in excluded_fields]
        values = []
        for field_name in field_names:
            # get specific value from instanced object.
            # and outputing as `string` value.
            values.append('%s' % getattr(self, field_name))

        # joining all string values.
        return ' | '.join(values)

如果我用public IEnumerable<T> Select(string sessionId, Func<T, bool> predicate = null) { using (var databaseContext = new DatabaseContext()) { var list = databaseContext.Set<T>().Where(predicate ?? (x => true)).AsQueryable<T>().ToList(); list.ForEach(o => o.SessionId = sessionId); return list; } }调用它，我希望它在sql中放置一个Select('sdfsdf', o => o.Category == 'Save Pewdiepie')子句，但它给了我这个没有where子句的内容：

where

对于大型表格来说，这将是一个大问题。如何更改它以创建SELECT [Extent1].[Id] AS [Id], [Extent1].[ClientId] AS [ClientId], [Extent1].[Version] AS [Version], [Extent1].[ReferenceNumber] AS [ReferenceNumber], [Extent1].[RealExpirationDate] AS [RealExpirationDate], [Extent1].[BusinessEffectiveDate] AS [BusinessEffectiveDate], [Extent1].[BusinessExpirationDate] AS [BusinessExpirationDate], [Extent1].[IsSuspended] AS [IsSuspended], [Extent1].[RealEffectiveDate] AS [RealEffectiveDate], [Extent1].[User] AS [User], [Extent1].[Category] AS [Category] FROM [dbo].[YouTube] AS [Extent1]子句？

Answer 1

我可以使用Expression来修复它：

public IEnumerable<T> Select(string sessionId, Expression<Func<T, bool>> predicate = null)
{
  using (var databaseContext = new DatabaseContext())
  {
    var list = databaseContext.Set<T>().Where(predicate ?? (x => true)).ToList();
    list.ForEach(o => o.SessionId = sessionId);
    return list;
  }
}

DatabaseContext.Set <t>不使用Sql中的where子句

1 个答案: