至少有一个对象必须实现icomparable。 LINQ C＃

问题描述

亲爱的所有人，



我有一个List，我正在申请GroupBy，Orderby&然后使用LINQ-C＃。



当我更改requestDate和备注时我得到以下错误。

Dear All,

I have a List and i'm appling GroupBy, Orderby & ThenBy using LINQ-C#.

When i change the requestDate and remarks i'm getting the following erro.

At least one object must implement IComparable.
Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details: System.ArgumentException: At least one object must implement IComparable.

什么我试过了：

What I have tried:

IEnumerable<CandidateRefundVoucherInfo> requestVouchers = CandidateRefundVoucherController.Instance.GetByCenterID(16);

            if (requestVouchers.Count() > 0)
            {
                var CandidateRefundVouchers = requestVouchers.
                    Select(items => new
                    {
                        CertificateID = items.Certificate.ID,
                        items.Certificate.Code,
                        items.Certificate.NameEN,
                        items.Certificate.NameAR,
                        items.Remarks,
                        items.RequestDate,
                        items.NumberOfRefundVoucherRequest,
                        items.StatusType,
                        UpdatedByUser = items.UpdatedByUser.NameEN
                    }).
                    GroupBy(i => new
                    {
                        i.CertificateID,
                        i.Code,
                        i.NameEN,
                        i.NameAR,
                        i.Remarks,
                        i.RequestDate,
                        i.NumberOfRefundVoucherRequest,
                        i.StatusType,
                        i.UpdatedByUser
                    })
                        .OrderByDescending(d => new { d.Key.RequestDate })
                        .ThenBy(l => new { l.Key.Remarks })
                        .Select(item => new
                        {
                            ID = item.Key.CertificateID,
                            Code = item.Key.Code,
                            NameEN = item.Key.NameEN,
                            NameAR = item.Key.NameAR,
                            RequestedVouchers = item.Sum(items => items.NumberOfRefundVoucherRequest),
                            Status = item.Key.StatusType,
                            RequestedDate = item.Key.RequestDate.ToString("dddd, dd MMMM yyyy"),
                            Remarks = item.Key.Remarks,
                            UpdatedBy = item.Key.UpdatedByUser,
                            BindLink = BindCode(item.Key.CertificateID, item.Key.Code)
                        });

                rptCandidateRefundVouchers.DataSource = CandidateRefundVouchers;
                rptCandidateRefundVouchers.DataBind();

任何人都可以帮助我。





谢谢

Can anyone please help me.


Thanks

推荐答案

IEnumerable<CandidateRefundVoucherInfo> candidateRefundVoucherList = requestVouchers;
                var refundVouchers = candidateRefundVoucherList.OrderByDescending(d => d.RequestDate).
                    GroupBy(r => r.RequestDate).Select(item => new {
                    ID = item.First().Certificate.ID,
                    Code = item.First().Certificate.Code,
                    NameEN = item.First().Certificate.NameEN,
                    NameAR = item.First().Certificate.NameAR,
                    RequestedVouchers = item.Sum(items => items.NumberOfRefundVoucherRequest),
                    Status = item.First().StatusType,
                    RequestedDate = item.First().RequestDate.ToString("dddd, dd MMMM yyyy"),
                    Remarks = item.First().Remarks,
                    UpdatedBy = item.First().UpdatedByUser.NameEN,
                    BindLink = BindCode(item.First().Certificate.ID, item.First().Certificate.Code, item.First().RequestDate.ToShortDateString())
                });

                rptCandidateRefundVouchers.DataSource = refundVouchers;
                rptCandidateRefundVouchers.DataBind();

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