[Solved]-Linq syntax to state explicit type instead of var-LINQ,C#

List<List<testobject>> wouldn't be the correct type. If you added a breakpoint on a line after and results1 is declared and inspected the type of it you would probably see something similar to List<IGrouping<string, testobject>>. If you want to declare explicit types use some means to figure out actual type, like a debugger, IDE or some plugin. ReSharper could give you a refactoring option to declare explicit type instead of var.

When you hover over the ToList() call in VisualStudio you can see that the return type is List<IGrouping<string, testobject>>

Try:

List<IGrouping<string, testobject>> results2 = testobjectList.Where(x => x.field1 >= 2)
                                                             .GroupBy(x => x.field2).ToList();

If you have ReSharper you can use the "Specify type explicitly" refactoring to convert the var statement to the explicit type.

You need to flatten your result by adding a .SelectMany() to strongly type the result as a List.

You also have the List declared as List<List> result 2 when it should be List

Working Sample:

List<testobject> results2 = testobjectList .Where(x => x.field1 >= 2)
                                                    .GroupBy(x=>x.field2)
                                                    .SelectMany(x=>x)
                                                    .ToList();