LINQ 分组结果并按特定顺序排序

Question

I want to order my data like this:

1. Group my data by some value called "Type"

2. I want to order groups by specific order of Types, for example: I have defined order: TYPE1, TYPE3, TYPE4,TYPE2

   And now I want all set to look like this:

   -first few rows are TYPE1 Type rows,

   -next few rows are TYPE3 Type rows,

   .....

Can anyone tell me how to achieve this?

Answer 1

You've mentioned that Type is an enum. I can see two easy options for ordering this, 1. change the value of the enumeration members or, 2. use a custom ordering.

Solution 1 - Changing enumeration member values

This is quite simple, but may not fit in with your requirements (ie the enumeration values may be dictated elsewhere or need hardcoded values).

Change the value of the enumeration members to be fixed values in the order you want:

public enumeration YourEnumName {
    TYPE1 = 1,
    TYPE3 = 2,
    TYPE4 = 3,
    TYPE2 = 4
}

Solution 2 - Use a custom list for ordering purposes

When conduction your ordering, create a list to dictate the order you want:

YourEnum[] orderList = new [] { YourEnum.TYPE1, YourEnum.TYPE3, YourEnum.TYPE4, YourEnum.TYPE2 };

var result = yourData.OrderBy(x => orderList.IndexOf(x.Type));

The limitation with this second solution is that if you have an item that does not exist in the orderList , then you will find that these are placed together in the order they were received at the start of the list. There are solutions to that issue but I'm not clear on whether you will experience it.