格式化十进制c＃ - 保持最后一个零

Question

I have been searching for this but cannot seem to find the answer. I have the following decimals with the corresponding output that I want from String.Format

100.00 -> 100
100.50 -> 100.50
100.51 -> 100.51

My problem is that I cannot seem to find a format which will keep the 0 on the end of 100.50 as well as remove the 2 zeros from 100.

Any help is much appreciated.

EDIT For some more clarity. I have variables of type decimal, they are only ever going to be 2 decimal places. Basically I want to display 2 decimal places if they exist or none, I don't want to display one decimal place in the case of 100.50 becoming 100.5

Answer 1

As far as I know, there is no such format. You will have to implement this manually, eg:

String formatString = Math.Round(myNumber) == myNumber ? 
                      "0" :     // no decimal places
                      "0.00";   // two decimal places

Answer 2

You can use this:

string s = number.ToString("0.00");
if (s.EndsWith("00"))
{
    s = number.ToString("0");
}

Answer 3

测试您的号码是否为整数，并使用以下格式：

string.Format((number % 1) == 0 ? "{0}": "{0:0.00}", number)

Answer 4

Ok, this hurts my eyes, but should give you what you want:

string output = string.Format("{0:N2}", amount).Replace(".00", "");

UPDATE: I like Heinzi's answer more.

Answer 5

This approach will achieve the desired result while applying the specified culture:

decimal a = 100.05m;
decimal b = 100.50m;
decimal c = 100.00m;

CultureInfo ci = CultureInfo.GetCultureInfo("de-DE");

string sa = String.Format(new CustomFormatter(ci), "{0}", a); // Will output 100,05
string sb = String.Format(new CustomFormatter(ci), "{0}", b); // Will output 100,50
string sc = String.Format(new CustomFormatter(ci), "{0}", c); // Will output 100

You can replace the culture with CultureInfo.CurrentCulture or any other culture to fit your needs.

The CustomFormatter class is:

public class CustomFormatter : IFormatProvider, ICustomFormatter
{
    public CultureInfo Culture { get; private set; }

    public CustomFormatter()
        : this(CultureInfo.CurrentCulture)
    { }

    public CustomFormatter(CultureInfo culture)            
    {
        this.Culture = culture;
    }

    public object GetFormat(Type formatType)
    {
        if (formatType == typeof(ICustomFormatter))
            return this;

        return null;
    }

    public string Format(string format, object arg, IFormatProvider formatProvider)
    {
        if (formatProvider.GetType() == this.GetType())
        {
            return string.Format(this.Culture, "{0:0.00}", arg).Replace(this.Culture.NumberFormat.NumberDecimalSeparator + "00", "");
        }
        else
        {
            if (arg is IFormattable)
                return ((IFormattable)arg).ToString(format, this.Culture);
            else if (arg != null)
                return arg.ToString();
            else
                return String.Empty;
        }
    }
}