我自己已经找到解决办法了,分享一下var query = DB.FullClient.Queryable<ContractOrders, Contracts>((co, cs) => new object[]{JoinType.Inner,co.ContractId==cs.Id}).WhereIF(!string.IsNullOrEmpty(customerId), (co, cs) => cs.CustomerId == customerId).WhereIF(startDate.HasValue, (co, cs) => cs.ActivateDate >= startDate.Value).WhereIF(endDate.HasValue, (co, cs) => cs.ActivateDate <= endDate.Value.AddDays(1)).WhereIF(status.HasValue, co => co.Status == status.Value).Select((co, cs) => new ContractOrdersP<Contracts>{Code = co.Code,Id = co.Id,CreateTime = co.CreateTime,ContractId = co.ContractId,Remark = co.Remark,Status = co.Status,Contracts = cs,TotalPrice = SqlFunc.Subqueryable<ProductConfigs>().Where(r => r.ContractOrderId == co.Id).GroupBy(r => r.ContractOrderId).Select(r => SqlFunc.AggregateSum(r.Quantity * r.DiscountPrice))});用这个函数可以解决, SqlSugar作者 定义了AggregateSum 这种方法, 一般人还真不知道

4.x.Max(it => it.id);.Sum(it => it.id);

 //子查询的版本var list = db.Queryable<TC020_Purchase>().Select(a => new{guid = a.TC020_Guid,compony = a.TC020_Company,SignDate = a.TC020_SignDate,ProjectTitle = a.TC020_ProjectTitle,Signer = a.TC020_Signer,ContractID = a.TC020_ContractID,PaymentClaus = a.TC020_PaymentClause,TotalCount = a.TC020_TotalAmount,paid = SqlFunc.Subqueryable<TC022_PurchasePaymentRecord>().Where(b => b.TC020_Guid == a.TC020_Guid).Select(b => SqlFunc.AggregateSum(b.TC022_NotPaid.Value)).ToString(),notpaid = SqlFunc.Subqueryable<TC022_PurchasePaymentRecord>().Where(b => b.TC020_Guid == a.TC020_Guid).Select(b => SqlFunc.AggregateSum(b.TC022_Paid.Value)).ToString()}).ToList();

  //Group by 版本var group = db.Queryable<TC020_Purchase, TC022_PurchasePaymentRecord>((a, b) => new object[] {JoinType.Left,a.TC020_Guid==b.TC020_Guid}).GroupBy(a => new {a.TC020_Guid,a.TC020_Company,a.TC020_SignDate,a.TC020_ProjectTitle,a.TC020_Signer,a.TC020_ContractID,a.TC020_PaymentClause,a.TC020_SalesContractID,a.TC020_TotalAmount}).Select((a,b)=> new {paid=SqlFunc.AggregateSum(b.TC022_NotPaid.Value).ToString(),notpaid= SqlFunc.AggregateSum(b.TC022_Paid.Value).ToString()}).ToList();