LINQ和放大器; String.ToLower（）的奇怪行为 [英] Linq & String.ToLower() strange behavior

问题描述

我已经在服务器端返回从邮编表不同城市的列表查询。

我使用WCF RIA服务。

下面的查询成功返回228个城市时， provincename ==

    public IQueryable<CityPM> GetCities(string provinceName)
    {
        return this.ObjectContext.ZipCodes.Where(z => z.Province.Contains(provinceName))
                                          .GroupBy(z => z.City)
                                          .Select(g => g.FirstOrDefault())
                                          .Select(zc => new CityPM() { ID = zc.ID, Name = zc.City });
    }

但如果我使用ToLower将（）方法如下，该查询返回0城市当 provincename ==

    public IQueryable<CityPM> GetCities(string provinceName)
    {
        return this.ObjectContext.ZipCodes.Where(z => z.Province.ToLower().Contains(provinceName.ToLower()))
                                          .GroupBy(z => z.City)
                                          .Select(g => g.FirstOrDefault())
                                          .Select(zc => new CityPM() { ID = zc.ID, Name = zc.City });
    }

为什么不是查询返回任何东西？

Why isn't the query returning anything?

推荐答案

尝试检查生成的SQL，通过使用DB管理工具，或者在查询表达式的末尾呼吁.ToTraceString（）。

Try checking the SQL generated, either by using DB management tools, or calling .ToTraceString() at the end of the query expression.

参考：的http：//博客。 aggregatedintelligence.com/2010/06/viewing-entity-framework-generated-sql.html

我们使用通过延长工作ToTraceString：

We use ToTraceString at work using an extension:

public static IQueryable<T> TraceSql<T>(this IQueryable<T> query)
{
    var sql = ((System.Data.Objects.ObjectQuery)query).ToTraceString();

    // do whatever logging of sql you want here, eg (for web)
    // (view by visiting trace.axd within your site)
    HttpContext.Current.Trace.Write("sql", sql);

    return query;
}

然后，它可以用作如下：

It can then be used as follows:

public IQueryable<CityPM> GetCities(string provinceName)
{
    return this.ObjectContext.ZipCodes.Where(z => z.Province.ToLower().Contains(provinceName.ToLower()))
                                      .GroupBy(z => z.City)
                                      .Select(g => g.FirstOrDefault())
                                      .Select(zc => new CityPM() { ID = zc.ID, Name = zc.City })
                                      .TraceSql();
}

请原谅我的拼写错误，这是从内存。希望它会帮助你了解你的问题。

Please forgive me for any typos, this is from memory. Hopefully it will help you understand your problem.

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