为什么LINQ to Entities无法识别方法'System.String ToString（）

Question

MVC3 Web应用程序内部出现错误。 LINQ to Entities does not recognize the method 'System.String ToString()' method, and this method cannot be translated into a store expression.

当我尝试使用EF从查询中获取值时：

public class DataRepository

    {

        public mydataEntities1 dbContext = new mydataEntities1();

        public List<SelectListItem> GetPricingSecurityID()

        {

        var pricingSecurityID = (from m in dbContext.Reporting_DailyNAV_Pricing

                                     select new SelectListItem

                                         {

                                                Text = m.PricingSecurityID.ToString(),

                                                Value = m.PricingSecurityID.ToString()

                                         });

        return pricingSecurityID.ToList();

        }

    }

Answer 1

那不能转换成SQL。我猜，从理论上讲，它可以，但是没有实现。得到结果后，只需执行投影即可：var pricingSecurityID = (from m in dbContext.Reporting_DailyNAV_Pricing&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;select m.PricingSecurityID).AsEnumerable()&nbsp; &nbsp; .Select(x => new SelectListItem{ Text = x.ToString(), Value = x.ToString() });

Answer 2

这个怎么样。在此示例中，db中的VDN字段和Skill字段都是整数。我正在寻找来自两个领域的比赛，所以我有2个比较。包括以下内容：using System.Data.Objects.SqlClient; // needed to convert numbers to strings for linq比较数字时，请执行以下操作：&nbsp; &nbsp; &nbsp; &nbsp; // Search Code&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; if (!String.IsNullOrEmpty(searchString))&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; {&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; depts = depts.Where(d => SqlFunctions.StringConvert((double)d.VDN).Contains(searchString.ToUpper())&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; || SqlFunctions.StringConvert((double)d.Skill).Contains(searchString.ToUpper()));&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; }&nbsp; &nbsp; &nbsp; &nbsp; // End Search Code工夫。