How to Convert Between Hexadecimal Strings and Numeric Types?

Introduction

In C#, working with hexadecimal strings and numeric types is a common requirement, especially when dealing with low-level programming, cryptography, or communication protocols. Converting between these representations is essential, and fortunately, C# provides straightforward methods to accomplish this task efficiently. In this article, we'll explore how to convert hexadecimal strings to numeric types and vice versa in C#.

These examples show you how to perform the following tasks:

Obtain the hexadecimal value of each character in a string.
Obtain the char that corresponds to each value in a hexadecimal string.
Convert a hexadecimal string to an int.
Convert a hexadecimal string to a float.
Convert a byte array to a hexadecimal string.

Example 1. Obtain the hexadecimal value of each character in a string

This example outputs the hexadecimal value of each character in a string. First, it parses the string to an array of characters. Then it calls ToInt32(Char) on each character to obtain its numeric value. Finally, it formats the number as its hexadecimal representation in a string.

string input = "Hello World!";
char[] values = input.ToCharArray();
foreach (char letter in values)
{
    // Get the integral value of the character.
    int value = Convert.ToInt32(letter);
    // Convert the integer value to a hexadecimal value in string form.
    Console.WriteLine($"Hexadecimal value of {letter} is {value:X}");
}
/* Output:
    Hexadecimal value of H is 48
    Hexadecimal value of e is 65
    Hexadecimal value of l is 6C
    Hexadecimal value of l is 6C
    Hexadecimal value of o is 6F
    Hexadecimal value of   is 20
    Hexadecimal value of W is 57
    Hexadecimal value of o is 6F
    Hexadecimal value of r is 72
    Hexadecimal value of l is 6C
    Hexadecimal value of d is 64
    Hexadecimal value of ! is 21
 */

Example 2. Obtain the char that corresponds to each value in a hexadecimal string

This example parses a string of hexadecimal values and outputs the character corresponding to each hexadecimal value.

First, it calls the Split(Char[]) method to obtain each hexadecimal value as an individual string in an array.

Then, it calls ToInt32(String, Int32) to convert the hexadecimal value to a decimal value represented as an int.

It shows two different ways to obtain the character corresponding to that character code.

The first technique uses ConvertFromUtf32(Int32), which returns the character corresponding to the integer argument as a string. The second technique explicitly casts the int to a char.

string hexValues = "48 65 6C 6C 6F 20 57 6F 72 6C 64 21";
string[] hexValuesSplit = hexValues.Split(' ');
foreach (string hex in hexValuesSplit)
{
    // Convert the number expressed in base-16 to an integer.
    int value = Convert.ToInt32(hex, 16);
    // Get the character corresponding to the integral value.
    string stringValue = Char.ConvertFromUtf32(value);
    char charValue = (char)value;
    Console.WriteLine("hexadecimal value = {0}, int value = {1}, char value = {2} or {3}",
                        hex, value, stringValue, charValue);
}
/* Output:
    hexadecimal value = 48, int value = 72, char value = H or H
    hexadecimal value = 65, int value = 101, char value = e or e
    hexadecimal value = 6C, int value = 108, char value = l or l
    hexadecimal value = 6C, int value = 108, char value = l or l
    hexadecimal value = 6F, int value = 111, char value = o or o
    hexadecimal value = 20, int value = 32, char value =   or
    hexadecimal value = 57, int value = 87, char value = W or W
    hexadecimal value = 6F, int value = 111, char value = o or o
    hexadecimal value = 72, int value = 114, char value = r or r
    hexadecimal value = 6C, int value = 108, char value = l or l
    hexadecimal value = 64, int value = 100, char value = d or d
    hexadecimal value = 21, int value = 33, char value = ! or !
*/

Example 3. Convert a hexadecimal string to an int

This example shows another way to convert a hexadecimal string to an integer by calling the Parse(String, NumberStyles) method.

string hexString = "8E2";
int num = Int32.Parse(hexString, System.Globalization.NumberStyles.HexNumber);
Console.WriteLine(num);
//Output: 2274

Example 4. Convert a hexadecimal string to a float

The following example shows how to convert a hexadecimal string to a float by using the System.BitConverter class and the UInt32.Parse method.

string hexString = "43480170";
uint num = uint.Parse(hexString, System.Globalization.NumberStyles.AllowHexSpecifier);

byte[] floatVals = BitConverter.GetBytes(num);
float f = BitConverter.ToSingle(floatVals, 0);
Console.WriteLine("float convert = {0}", f);

// Output: 200.0056

Example 5. Convert a byte array to a hexadecimal string

The following example shows how to convert a byte array to a hexadecimal string by using the System.BitConverter class.

byte[] vals = [0x01, 0xAA, 0xB1, 0xDC, 0x10, 0xDD];

string str = BitConverter.ToString(vals);
Console.WriteLine(str);

str = BitConverter.ToString(vals).Replace("-", "");
Console.WriteLine(str);

/*Output:
  01-AA-B1-DC-10-DD
  01AAB1DC10DD
 */

Example 6. Convert a byte array to a hexadecimal string

The following example shows how to convert a byte array to a hexadecimal string by calling the Convert.ToHexString method introduced in .NET 5.0.

byte[] array = [0x64, 0x6f, 0x74, 0x63, 0x65, 0x74];

string hexValue = Convert.ToHexString(array);
Console.WriteLine(hexValue);

/*Output:
  646F74636574
 */

Conclusion

Converting hexadecimal strings to numeric types and vice versa is a common operation in C# programming. By utilizing the provided methods such as Convert.ToInt32, Convert.ToInt64, int.Parse, and ToString with the "X" format specifier, you can seamlessly perform these conversions. Remember to handle invalid input gracefully to ensure the robustness of your code. Whether you're working on low-level tasks or high-level applications, having a good understanding of these conversion techniques can significantly enhance your programming capabilities in C#.