linq to lucene错误:“类必须将至少一个字段定义为默认搜索字段”

我的linq to sql类应用了以下属性:

[Document(MetadataType = typeof(SomeObjectMetadata))]
public partial class SomeObject
{
}

这是元数据代码:

public class SomeObjectMetadata
{

    [Field(FieldIndex.Tokenized, FieldStore.Yes, IsKey = true)]  
    private object ProductId { get; set; }

    [Field(FieldIndex.Tokenized, FieldStore.Yes, IsDefault = true)]  
    private object Name { get; set; }

    [Field(FieldIndex.Tokenized, FieldStore.Yes)]  
    private object Description { get; set; }

    [Field(FieldIndex.Tokenized, FieldStore.Yes)] 
    private object Breadcrumb { get; set; }

    [Field(FieldIndex.Tokenized, FieldStore.Yes)] 
    private object Tab1Content { get; set; }

    [Field(FieldIndex.Tokenized, FieldStore.Yes)] 
    private object Tab2Content { get; set; }

    [Field(FieldIndex.Tokenized, FieldStore.Yes)] 
    private object Tab3Content { get; set; }

    [Field(FieldIndex.Tokenized, FieldStore.Yes)] 
    private object Tab4Content { get; set; }

    [Field(FieldIndex.Tokenized, FieldStore.Yes)] 
    private object Tab5Content { get; set; }

    [Field(FieldIndex.Tokenized, FieldStore.Yes)] 
    private object Manufacturer { get; set; }

}

索引存储写得很好,但是当我尝试搜索它时,我得到了标题中显示的错误。下面是一个示例搜索:

        var qry = from r in _dbi.Get<SomeObject>()
                  where r.Description.Like(search)
                  select r;

枚举“qry”时,抛出异常“类必须至少定义一个字段作为默认搜索字段”。