Formatted output in C#

In C#, formatted output allows you to control how data is displayed when converting values to strings. This is essential for presenting numbers, dates, and other data types in a user-friendly format using format specifiers and the String.Format() method.

Syntax

Following is the syntax for basic string formatting −

String.Format("{index:format}", value)

Where index is the parameter position (starting from 0) and format is the format specifier.

Using Format Specifiers for Numbers

Decimal Places and Thousands Separator

using System;

class Demo {
    public static void Main(String[] args) {

        Console.WriteLine("Three decimal places...");
        Console.WriteLine(String.Format("{0:0.000}", 987.383));
        Console.WriteLine(String.Format("{0:0.000}", 987.38));
        Console.WriteLine(String.Format("{0:0.000}", 987.7899));

        Console.WriteLine("Thousands Separator...");
        Console.WriteLine(String.Format("{0:0,0.0}", 54567.46));
        Console.WriteLine(String.Format("{0:0,0}", 54567.46));
    }
}

The output of the above code is −

Three decimal places...
987.383
987.380
987.790
Thousands Separator...
54,567.5
54,567

Currency and Percentage Formatting

using System;

class Demo {
    public static void Main(String[] args) {
        double price = 1234.56;
        double percentage = 0.75;

        Console.WriteLine("Currency format: " + String.Format("{0:C}", price));
        Console.WriteLine("Percentage format: " + String.Format("{0:P}", percentage));
        Console.WriteLine("Fixed-point format: " + String.Format("{0:F2}", price));
        Console.WriteLine("Number format: " + String.Format("{0:N}", price));
    }
}

The output of the above code is −

Currency format: $1,234.56
Percentage format: 75.00%
Fixed-point format: 1234.56
Number format: 1,234.56

Using Format Specifiers for DateTime

using System;

static class Demo {
    static void Main() {

        DateTime d = new DateTime(2018, 2, 8, 12, 7, 7, 123);
        Console.WriteLine(String.Format("{0:y yy yyy yyyy}", d));
        Console.WriteLine(String.Format("{0:M MM MMM MMMM}", d));
        Console.WriteLine(String.Format("{0:d dd ddd dddd}", d));
        Console.WriteLine(String.Format("{0:h hh H HH}", d));
        Console.WriteLine(String.Format("{0:m mm s ss}", d));
    }
}

The output of the above code is −

18 18 2018 2018
2 02 Feb February
8 08 Thu Thursday
12 12 12 12
7 07 7 07

Standard DateTime Format Strings

using System;

class Demo {
    public static void Main() {
        DateTime now = DateTime.Now;

        Console.WriteLine("Short date: " + String.Format("{0:d}", now));
        Console.WriteLine("Long date: " + String.Format("{0:D}", now));
        Console.WriteLine("Short time: " + String.Format("{0:t}", now));
        Console.WriteLine("Long time: " + String.Format("{0:T}", now));
        Console.WriteLine("Full date/time: " + String.Format("{0:F}", now));
    }
}

The output of the above code is −

Short date: 12/25/2023
Long date: Monday, December 25, 2023
Short time: 3:45 PM
Long time: 3:45:30 PM
Full date/time: Monday, December 25, 2023 3:45:30 PM

Common Format Specifiers

Conclusion

Formatted output in C# provides precise control over how data is displayed using format specifiers with String.Format(). Whether formatting numbers with specific decimal places, adding thousands separators, or displaying dates in various formats, these tools ensure your output is professional and user-friendly.