Question

I’m currently stuck at a problem where I have 2 Lists, and I want to sort the second List according to a value from the first List, here is an example:

public class data
{
    public string Name{get; set;}
    public int ID{get; set}
}
public class dataToSort
{
    public int ID{get; set;}
    public string retrievedData{get; set}
    public string timeStamp{get; set}
}

So lets say I have 2 List objects, one for data and one for dataToSort, their contents below:

data: "Alpha", "80"           dataToSort: "21", "XA", "YA"
      "Beta", "47"                        "47", "XB", "YB"
      "Charlie", "153"                    "80", "XC", "YC"
      "Delta", "21"                       "153","XD", "YD"

So what I want to do is to make the order of dataToSort equal to the order of the IDs in data, like this:

dataToSort: "80", "XC", "YC"
            "47", "XB", "YB"
            "153","XD", "YD"
            "21", "XA", "YA"

I have tried googling for a way to Sort these but all the LINQ syntax confuses me and I have problems due to the difference in classes of each object 🙁 The only way I can think of is to have a for loop to get the index of one List’s ID and do something like a bubble sort, but its too much of a hassle and also inefficient. Help is greatly appreciated!

Answer 1

You can join the two lists on the IDs:

var query = from x in data
            join y in dataToSort on x.ID equals y.ID
            select y;

var result = query.ToList();

This keeps the order of the first list data.

---

You can also easily combine the two lists this way:

var query = from x in data
            join y in dataToSort on x.ID equals y.ID
            select new
            {
                x.Name,
                x.ID,
                y.retrievedData,
                y.timeStamp,
            };

var result = query.ToList();