C# Hexadecimal ("X") Format Specifier

The hexadecimal ("X") format specifier is used to convert a number to a string of hexadecimal digits. The case of the format specifier determines whether hexadecimal digits greater than 9 are displayed in uppercase or lowercase.

Use "X" for uppercase hexadecimal letters (A, B, C, D, E, F) and "x" for lowercase hexadecimal letters (a, b, c, d, e, f).

Syntax

Following is the syntax for using the hexadecimal format specifier −

number.ToString("X")     // uppercase
number.ToString("x")     // lowercase
number.ToString("X4")    // uppercase with minimum 4 digits
number.ToString("x8")    // lowercase with minimum 8 digits

Basic Hexadecimal Formatting

Example

using System;

class Demo {
    static void Main() {
        int num = 345672832;
        Console.WriteLine("Decimal: " + num);
        Console.WriteLine("Uppercase hex: " + num.ToString("X"));
        Console.WriteLine("Lowercase hex: " + num.ToString("x"));
        
        num = 0x307e;
        Console.WriteLine("\nDecimal: " + num);
        Console.WriteLine("Uppercase hex: " + num.ToString("X"));
        Console.WriteLine("Lowercase hex: " + num.ToString("x"));
    }
}

The output of the above code is −

Decimal: 345672832
Uppercase hex: 149A8C80
Lowercase hex: 149a8c80

Decimal: 12414
Uppercase hex: 307E
Lowercase hex: 307e

Using Precision Specifiers

You can specify the minimum number of digits by adding a precision specifier after the format specifier −

Example

using System;

class Demo {
    static void Main() {
        int num = 255;
        Console.WriteLine("Default: " + num.ToString("X"));
        Console.WriteLine("2 digits: " + num.ToString("X2"));
        Console.WriteLine("4 digits: " + num.ToString("X4"));
        Console.WriteLine("8 digits: " + num.ToString("X8"));
        
        Console.WriteLine("\nLowercase with padding:");
        Console.WriteLine("4 digits: " + num.ToString("x4"));
        Console.WriteLine("6 digits: " + num.ToString("x6"));
    }
}

The output of the above code is −

Default: FF
2 digits: FF
4 digits: 00FF
8 digits: 0000FF

Lowercase with padding:
4 digits: 00ff
6 digits: 0000ff

Working with Different Data Types

Example

using System;

class Demo {
    static void Main() {
        byte b = 255;
        short s = -1;
        int i = 16777215;
        long l = 281474976710655L;
        
        Console.WriteLine("byte 255: " + b.ToString("X2"));
        Console.WriteLine("short -1: " + s.ToString("X4"));
        Console.WriteLine("int 16777215: " + i.ToString("X6"));
        Console.WriteLine("long value: " + l.ToString("X12"));
        
        Console.WriteLine("\nUsing lowercase:");
        Console.WriteLine("RGB color: #" + i.ToString("x6"));
    }
}

The output of the above code is −

byte 255: FF
short -1: FFFF
int 16777215: FFFFFF
long value: FFFFFFFFFFFF

Using lowercase:
RGB color: #ffffff

Common Use Cases

• Color values: Converting RGB values to hexadecimal for web colors (e.g., #FF0000 for red).

• Memory addresses: Displaying memory locations in hexadecimal format.

• Binary data: Representing byte arrays or binary data in readable hexadecimal format.

• Debugging: Viewing numeric values in hexadecimal for easier bit manipulation analysis.

Conclusion

The hexadecimal format specifier "X" converts numbers to hexadecimal strings, with "X" producing uppercase letters and "x" producing lowercase letters for digits A-F. Precision specifiers can be added to control minimum digit count with zero-padding when needed.