在LINQ查询中分组

我有一个DataTable，我想在其上执行GroupBy查询。

year url type id ============================= someurl image 0 2003 date 0 someurl image 1 2009 date 1 

我已经设法对我的ID进行分组，但我无法选择“年”和“Url”列。

这是我的查询：

 var query = from row in table.AsEnumerable() let uri = row["uri"] group row by row.Field("id") into grp orderby grp.Key select new { ID = grp.Key, }; 

如何选择列年份和url？

提前致谢。

Answer 1

当您在LINQ中分组时，您的组（grp）是一个可枚举的，包含组中的所有条目（在您的情况下为数据行）。 然后，您可以预先输入条目或使用Max，First等聚合函数从枚举中提取单个值

Answer 2

您可以按多个值进行分组。 在您的案例组中按ID，年份和url点击此处

  List webResources = new List(); webResources.Add(new WebResource() { Id = 1, Type = "Image", Url = "url1", Year = 2001 }); webResources.Add(new WebResource() { Id = 1, Type = "Text", Url = "url1", Year = 2001 }); webResources.Add(new WebResource() { Id = 3, Type = "Image", Url = "url1", Year = 2001 }); webResources.Add(new WebResource() { Id = 1, Type = "Text", Url = "url1", Year = 2002 }); webResources.Add(new WebResource() { Id = 2, Type = "Image", Url = "url1", Year = 2002 }); webResources.Add(new WebResource() { Id = 3, Type = "Text", Url = "url2", Year = 2002 }); webResources.Add(new WebResource() { Id = 1, Type = "Image", Url = "url1", Year = 2002 }); webResources.Add(new WebResource() { Id = 2, Type = "Text", Url = "url2", Year = 2002 }); var output = webResources.GroupBy(webResource => new {webResource.Id, webResource.Year, webResource.Url }) .Select(group => new {Key = group.Key, Count = group.Count()}); foreach (var webResource in output) { Console.WriteLine("Id: " + webResource.Key.Id +" Url:" + webResource.Key.Url + " Year:" + webResource.Key.Year + " Count:" + webResource.Count); }