关于Linq Query中的ArrayIndex

Question

当我尝试执行以下时，LINQ到实体的LINQ错误中没有支持LINQ表达式节点类型ArrayIndex

public List<AttachmentList> ShowAttachments(int type, int ReferenceId)
{
    try
    {
        var attachmentNames =
            (from attachment in tent.Attachments
                where (attachment.Attachment_Type == type
                    && attachment.Attachment_Reference_Pk == ReferenceId)
                select new AttachmentList
                        {
                            Attachment_Pk = attachment.Attachment_Pk,
                            Attachment_File_Path = attachment
                                .Attachment_File_Path.Split(new[] {'$'})[1]
                        }).ToList();
        return attachmentNames;
    }
    catch (Exception ex)
    {
        ExceptionHandler.ExceptionLog(ex);
        return null;
    }
} 

如您所见，我正在尝试拆分包含'$'的Attachmentfilepath，并将第二个值（[1]）分配给Attachment_FilePath

有人能建议我如何在同一查询中拆分并将值分配给AttachmentList字符串吗感谢

Answer 1

老实说，最简单的方法是在客户端进行拆分，除非真的需要它成为一个成熟的实体。例如：

var query = from attachment in tent.Attachments
            where attachment.Attachment_Type == type &&
                  attachment.Attachment_Reference_Pk == ReferenceId
            select new { Attachment_Pk, Attachment_File_Path };
// Force the rest to execute client-side.
var attachmentNames = query.AsEnumerable()
                           .Select(x => new AttachmentList {
                               Attachment_Pk = x.Attachment_Pk,
                               Attachment_File_Path = x.Attachment_File_Path
                                                       .Split('$')[1]
                           })
                           .ToList();

Answer 2

您可以先投影到一个匿名类来获取所需的数据，然后切换到使用Linq来处理使用AsEnumerable():支持这种操作的对象

var attachmentNames = (from attachment in tent.Attachments
                        where (attachment.Attachment_Type == type && attachment.Attachment_Reference_Pk == ReferenceId)
                        select new { attachment.Attachment_Pk, attachment.Attachment_File_Path })
                        .AsEnumerable()
                        .Select(attachment =>
                        new AttachmentList
                        {
                            Attachment_Pk = attachment.Attachment_Pk,
                            Attachment_File_Path = attachment.Attachment_File_Path.Split(new[] { '$' })[1]
                        }).ToList();