LINQ顺序由十进制字段排序像一个字符串？

Question

I'm totally baffled and cannot find anything on the internet about this, so I must be doing something wrong?

 _positionsRepo.GetAllTrades().OrderByDescending(x => x.TotalPLPercent).ToList();

TotalPLPercent is a decimal field. the result order sorts like this:

96.76
95.54
8.54
75.55
231.22
13

Obviously, this is wrong. I tested the sort against another field that was a double, and it worked as expected. What am I missing here about decimals in C#?

I am using the Mongo DB C# driver.

Answer 1

The C# Mongo DB driver serializes decimal as a string (The driver source-code corroborates this).

It does this because there is no BSON type for decimal - double does not have the same precision. Unfortunately it means you can't compare "decimal" values as numbers.

You could sort the data in memory, like this:

_positionsRepo.GetAllTrades()
   .ToList()
   .OrderByDescending(x => x.TotalPLPercent)
   .ToList();

Another option would be to store the number of cents (or hundredths of cents) as a long integer. Then you can sort them normally, and you just have to divide by 100 (or 10,000) to get your real value.

Answer 2

Apparently, this is the problem with MongoDB Driver for C# . Check this open issue here -

the 'System.Decimal' type save as 'String'

As you can see since Decimal is saved as String , it surely will sort like a string. I think you should try double instead of decimal until they fix this issue.

Answer 3

Are you sure the type of x is Decimal? It looks like it's doing a string ordering. (I'd put a breakpoint on "x.TotalPLPercent" and then evaluate x's type to double verify it's what I thought it was.)