README.md

NumberStringComparer

A C# Comparer to sort lists of data that could be either numeric of string replacing the default alphabetical sort which doesn't always work for numbers.

The Problem

The default alphabetical sort doesn't work when numbers are stored as strings.
Example 1:

var list1 = new List<string>(){
    "1",
    "2",
    "3",
    "10",
    "11",
    "100",
};
list1.Sort();

// Result: string.Join(Environment.NewLine, list1);

"1"
"10"
"100"
"11"
"2"
"3"

Example 2:

var list3 = new List<object>(){
    "1",
    "2",
    "3",
    "10",
    "11",
    "100",
    "A",
    "a",
    "b",
    "ab",
};
list3.Sort();

// Result: 
"1"
"10"
"100"
"11"
"2"
"3"
"A"
"a"
"b"
"ab"

Example 3: Combined lists containing both numbers and strings because you can't parse every item as numbers and it fails to compare items of different types.

var list3 = new List<object>(){
    1,
    2,
    3,
    10,
    11,
    100,
    "A",
    "a",
    "b",
    "ab",
};
list3.Sort();

Result:
- InvalidOperationException: 'Failed to compare two elements in the array.'

Solution

NumberStringComparer<T> parses each item into a NumberString<T> object composed of a text property containing the original text and if the item is numeric also a number component. If an item is not completely numeric, number will be null and the text is parsed into a list of parts containing the text broken up into its numeric and non-numeric parts.
e.g. "a122bc4" will result in parts = ["a", 122, "bc", 4]
Items are compared by number if they are completely numeric, otherwise each parts list will be compared for sorting. If the text contains commas, is broken up into a parts array of numbers, removing the commas. e.g. "1,2,3" will result in [1, 2, 3] and "1,2" will result in [1, 2] and when sorting, "1,2" will come before "1,2,3"

Comparing complex objects by 1 property

You can use any of the following primitive collection types

Supported data types

• string
• int
• double
• float
• decimal
• long
• short

As well as complex objects or Dictionaries using a property. For Dictionaries, it will use the key property of KeyValuePair and ignore the Value property. See NumberStringComparerTests.NumberStringComparerObjectComparison_Tests() for more complex object comparison examples.

.NET Version

This project uses .NET 7.0 (Core) for the main branch but there is also a .NET Framework-compatible branch made with only a few minor changes.

• Replacing readonly properties with private fields and properties with private do nothing setters.
• Replace uses of the Range operator with the SubStringSafe extension methods.
• Explicitly specify the object type on the right hand of equals replacing new()