使实体框架Linq查询异步

Question

我有一个在Winform应用程序中填充组合框的函数。 该操作需要几秒钟，所以我想使其异步。

这是函数：

public static List<string> GetAllPostCodeRegions(string country)
{
    using (var db = new PlaceDBContext())
    {
        var regions = db.PostCodes.Where(pc => pc.Country == country).OrderBy(pc => pc.Region).Select(pc => pc.Region).Distinct().ToList();

        return regions;
    }
}

我尝试只添加如下异步关键字：

public async static Task<List<string>> GetAllPostCodeRegions(string country)
{
    using (var db = new PlaceDBContext())
    {
        var regions = db.PostCodes.Where(pc => pc.Country == country).OrderBy(pc => pc.Region).Select(pc => pc.Region).Distinct().ToList();

        return regions;
    }
}

但这并没有等待什么，并且在我打电话时UI仍然锁定：

var regions = await DataFunctions.GetAllPostCodeRegions("UK");

如何使此操作异步并停止UI锁定？

Answer 1

您可以尝试.ToListAsync或：

public static Task<List<string>> GetAllPostCodeRegions(string country)
{
    return Task.Run(() => 
       {
          using (var db = new PlaceDBContext())
          {
               return db.PostCodes
                        .Where(pc => pc.Country == country)
                        .OrderBy(pc => pc.Region)
                        .Select(pc => pc.Region).Distinct().ToList();
          }
      });        
}