String Formatting with ToString in C#

The ToString() method in C# is a powerful way to format values into strings using various format specifiers. It provides control over how numbers, dates, and other data types are displayed as text.

Syntax

Following is the basic syntax for using ToString() with format specifiers −

variable.ToString("formatSpecifier");

For numeric formatting with custom patterns −

number.ToString("000");    // Zero padding
number.ToString("C");      // Currency format
number.ToString("F2");     // Fixed-point with 2 decimals

Using Zero Padding Format

The zero padding format ensures a number is displayed with a minimum number of digits, adding leading zeros if necessary −

using System;

public class Program {
    public static void Main() {
        int value = 55;
        string res = value.ToString("000");
        Console.WriteLine("Formatted value: " + res);
        
        int smallValue = 7;
        Console.WriteLine("Small value: " + smallValue.ToString("0000"));
    }
}

The output of the above code is −

Formatted value: 055
Small value: 0007

Using Standard Numeric Format Specifiers

using System;

public class Program {
    public static void Main() {
        double value = 1234.567;
        
        Console.WriteLine("Currency: " + value.ToString("C"));
        Console.WriteLine("Fixed-point 2 decimals: " + value.ToString("F2"));
        Console.WriteLine("Percentage: " + (0.85).ToString("P"));
        Console.WriteLine("Scientific: " + value.ToString("E"));
    }
}

The output of the above code is −

Currency: $1,234.57
Fixed-point 2 decimals: 1234.57
Percentage: 85.00%
Scientific: 1.234567E+003

Using DateTime Formatting

using System;

public class Program {
    public static void Main() {
        DateTime now = DateTime.Now;
        
        Console.WriteLine("Short date: " + now.ToString("d"));
        Console.WriteLine("Long date: " + now.ToString("D"));
        Console.WriteLine("Custom format: " + now.ToString("yyyy-MM-dd HH:mm:ss"));
        Console.WriteLine("Month/Year: " + now.ToString("MMMM yyyy"));
    }
}

The output of the above code is −

Short date: 12/15/2023
Long date: Friday, December 15, 2023
Custom format: 2023-12-15 14:30:45
Month/Year: December 2023

Common Format Specifiers

Conclusion

The ToString() method with format specifiers provides flexible string formatting for numbers, dates, and other data types. It offers both standard formats like currency and percentage, as well as custom patterns for specific formatting needs.