NumericUpDown StringFormat doesn't handle percentages correctly.

There’s strange behaviour happening with NumericUpDown’s StringFormat property, particularly around percentages.

First it looks like the P, % & ‰ format specifiers are being ignored, but when adding those same symbols outside of a format item, the numbers appear to be divided by 100 or 1000.

I do remember more frustrating issues before however - particularly with editing values. Previously, the numbers would look correct initially. After editing, the real value would be multiplied repeatedly.

To Reproduce:

Case 1:

1. Set NumericUpDown.StringFormat to {0:0.00%} or 0.00%
2. Set NumericUpDown.Value to 0.25
3. See that the label now shows 0.25% (expected 25.00%)

Case 2:

1. Set NumericUpDown.StringFormat to {0:0.00‰} or 0.00‰
2. Set NumericUpDown.Value to 0.25
3. See that the label now shows 0.25‰ (expected 250.00%)

Case 3:

1. Set NumericUpDown.StringFormat to {0:0.0000}%
2. Set NumericUpDown.Value to 0.25
3. See that the label now shows 0.0025% (expected 0.2500%)
4. Additionally, editing this number causes further division to the real value.

Case 4:

1. Set NumericUpDown.StringFormat to {0:0.00000}‰
2. Set NumericUpDown.Value to 0.25
3. See that the label now shows 0.00025‰ (expected 0.25000‰)
4. Additionally, editing this number causes further division to the real value.

Case 5:

1. Set NumericUpDown.StringFormat to P
2. Set NumericUpDown.Value to 0.25
3. See that the label now shows 0.25% (expected 25.00 %)

Environment:

• MahApps.Metro version 2.0.0-alpha0083
• OS: Win10 1803
• Visual Studio 2017 15.7.1
• .NET Framework 4.6.2

[punker76]

Make sure you have a test for the following combination

StringFormat={}{0}% Value=100 Text=100%

This would be how you get the percentage sign without any conversion.

Other than that, looking good @punker76

[punker76]

@mgnslndh @timunie The same with ‰

>> value: 100  => ‰      => 100‰
>> value: 1    => ‰      => 1‰
>> value: 0.1  => ‰      => 0.1‰
>> value: 0.01 => ‰      => 0.01‰

>> value: 100  => 0‰     => 100000‰
>> value: 1    => 0‰     => 1000‰
>> value: 0.1  => 0‰     => 100‰
>> value: 0.01 => 0‰     => 10‰

>> value: 100  => 0.0‰   => 100000.0‰
>> value: 1    => 0.0‰   => 1000.0‰
>> value: 0.1  => 0.0‰   => 100.0‰
>> value: 0.01 => 0.0‰   => 10.0‰

>> value: 100  => 0.000‰ => 100000.000‰
>> value: 1    => 0.000‰ => 1000.000‰
>> value: 0.1  => 0.000‰ => 100.000‰
>> value: 0.01 => 0.000‰ => 10.000‰

using System;
using System.Collections.Generic;
using System.Linq;

public class Program
{
  public static void Main()
  {
    Console.WriteLine($">> value: 100  => ‰      => {100}‰");
    Console.WriteLine($">> value: 1    => ‰      => {1}‰");
    Console.WriteLine($">> value: 0.1  => ‰      => {0.1}‰");
    Console.WriteLine($">> value: 0.01 => ‰      => {0.01}‰");
    Console.WriteLine();
    Console.WriteLine($">> value: 100  => 0‰     => {100:0‰}");
    Console.WriteLine($">> value: 1    => 0‰     => {1:0‰}");
    Console.WriteLine($">> value: 0.1  => 0‰     => {0.1:0‰}");
    Console.WriteLine($">> value: 0.01 => 0‰     => {0.01:0‰}");
    Console.WriteLine();
    Console.WriteLine($">> value: 100  => 0.0‰   => {100:0.0‰}");
    Console.WriteLine($">> value: 1    => 0.0‰   => {1:0.0‰}");
    Console.WriteLine($">> value: 0.1  => 0.0‰   => {0.1:0.0‰}");
    Console.WriteLine($">> value: 0.01 => 0.0‰   => {0.01:0.0‰}");
    Console.WriteLine();
    Console.WriteLine($">> value: 100  => 0.000‰ => {100:0.000‰}");
    Console.WriteLine($">> value: 1    => 0.000‰ => {1:0.000‰}");
    Console.WriteLine($">> value: 0.1  => 0.000‰ => {0.1:0.000‰}");
    Console.WriteLine($">> value: 0.01 => 0.000‰ => {0.01:0.000‰}");
  }
}