序列包含多个元素 Mvc

Question

问题函数 以下是我遇到问题的功能。我不断收到“序列包含多个元素”错误。这是假设的。但是，我不确定如何返回信息以便我可以使用它。任何帮助，将不胜感激。

EditCountyViewModel 是一个小类，其中包含 public County countypublic List CountyList. I have also tried changing the Read<> toRead`，它只是我所有县信息的基类。

public EditCountyViewModel FindByCounty(string countyName)
        {
            var parameters = new DynamicParameters();
            parameters.Add("@CountyName", value: countyName);

            var query = @"SELECT counties.id
                            , counties.CountyName
                            , counties.Website
                            , counties.Address
                            , counties.City
                            , counties.State
                            , counties.PhonePrimary
                            , counties.PhoneAlt
                            , counties.RecordsOnline
                            , counties.BackToYear
                            , counties.Cost
                            , products.ProductName
                            , products.Description
                            , countyproduct.TurnTime_MinHours
                            , countyproduct.TurnTime_MaxHours
                            , countyproduct.Price
                        FROM
                            counties, countyproduct, products
                        WHERE
                            counties.CountyName = @CountyName AND countyproduct.countiesID = countyproduct.countiesID AND countyproduct.productsID = products.ID;";

            //using (var multi = this.db.QueryMultipl(query, new { countyName }))
            //{
            //    EditCountyViewModel editVM = new EditCountyViewModel();
            //    editVM.county = multi.Read<County>().Single();
            //    return editVM;
            //}
            return this.db.Query<EditCountyViewModel>(query, parameters).SingleOrDefault();

        }

我想我需要另一个类来处理来自countyproduct 和products 表的项目。

Answer 1

SingleOrDefault() 确保只返回 1 条记录，如果有更多则抛出。如果您只想抢到第一个，请使用FirstOrDefault()。