如何在LINQ中使用union all？

如何在LINQ TO SQL中使用union all。 我已经使用下面的代码联合，那么如何使用这个工会所有？

List<tbEmployee> lstTbEmployee = obj.tbEmployees.ToList(); List<tbEmployee2> lstTbEmployee2 = (from a in lstTbEmployee select new tbEmployee2 { eid = a.eid, ename = a.ename, age = a.age, dept = a.dept, doj = a.doj, dor = a.dor }).Union(obj.tbEmployee2s).ToList(); 

Answer 1

Concat是SQL中UNION ALL的LINQ等价物。

我在LINQPad中设置了一个简单的例子来演示如何使用Union和Concat 。 如果你没有LINQPad ，得到它。

为了能够看到这些设置操作的不同结果，第一组和第二组数据必须至less有一些重叠。 在下面的例子中，两个集合都包含单词“不”。

打开LINQPad并将语言下拉菜单设置为C＃语句。 将以下内容粘贴到查询窗格中并运行它：

 string[] jedi = { "These", "are", "not" }; string[] mindtrick = { "not", "the", "droids..." }; // Union of jedi with mindtrick var union = (from word in jedi select word).Union (from word in mindtrick select word); // Print each word in union union.Dump("Union"); // Result: (Note that "not" only appears once) // These are not the droids... // Concat of jedi with mindtrick (equivalent of UNION ALL) var unionAll = (from word in jedi select word).Concat (from word in mindtrick select word); // Print each word in unionAll unionAll.Dump("Concat"); // Result: (Note that "not" appears twice; once from each dataset) // These are not not the droids... // Note that union is the equivalent of .Concat.Distinct var concatDistinct = (from word in jedi select word).Concat (from word in mindtrick select word).Distinct(); // Print each word in concatDistinct concatDistinct.Dump("Concat.Distinct"); // Result: (same as Union; "not" only appears once) // These are not the droids... 

LinqPad中的结果如下所示：