Hash Function for String data in C#
Last Updated :
05 Nov, 2024
In C#, hash functions are used to convert input data (like strings) into a fixed-size numerical value, commonly known as a hash code. This hash code can be utilized for various purposes, including data retrieval in hash tables, data integrity verification, and ensuring efficient storage and comparison operations.
Example
Input: "Hello, Geeks!"
Output: 1077004745 (This will vary based on the hash function used)
Syntax
public override int GetHashCode(); # Using GetHashCode Method
Using GetHashCode Method
The GetHashCode method is a built-in function that returns the hash code for the current instance of the string.
Syntax
public override int GetHashCode();
Example
C#
using System;
namespace HashFunctionExample {
class Program {
static void Main(string[] args) {
string input = "Hello, Geeks!";
int hashCode = input.GetHashCode();
Console.WriteLine("Hash Code: {0}", hashCode);
}
}
}
OutputHash Code: 1077004745
Other Method’s Include:
Using SHA256 Hash Algorithm
The SHA256 class from the System.Security.Cryptography namespace provides a more secure way to compute the hash value of a string.
Syntax:
public static SHA256 Create();
Example
C#
using System;
using System.Security.Cryptography;
using System.Text;
namespace HashFunctionExample {
class Program {
static void Main(string[] args) {
string input = "Hello, Geeks!";
using (SHA256 sha256Hash = SHA256.Create()) {
byte[] bytes = sha256Hash.ComputeHash(Encoding.UTF8.GetBytes(input));
StringBuilder builder = new StringBuilder();
foreach (byte b in bytes) {
builder.Append(b.ToString("x2")); // Convert to hexadecimal string
}
Console.WriteLine("SHA256 Hash: {0}", builder.ToString());
}
}
}
}
OutputSHA256 Hash: ec3a1612824c04a774ac0d81b3e97fb1c03c0c7e1c51117f9bc4ec1cfa07484b
Using MD5 Hash Algorithm
The MD5 class is another hashing algorithm, although it is not recommended for security-sensitive applications due to vulnerabilities.
Syntax
public static MD5 Create();
Example:
C#
using System;
using System.Security.Cryptography;
using System.Text;
namespace HashFunctionExample {
class Program {
static void Main(string[] args) {
string input = "Hello, Geeks!";
using (MD5 md5Hash = MD5.Create()) {
byte[] bytes = md5Hash.ComputeHash(Encoding.UTF8.GetBytes(input));
StringBuilder builder = new StringBuilder();
foreach (byte b in bytes) {
builder.Append(b.ToString("x2")); // Convert to hexadecimal string
}
Console.WriteLine("MD5 Hash: {0}", builder.ToString());
}
}
}
}
OutputMD5 Hash: f050f21f12381c503f1b17b452027274
Hash Function Using ASCII Values
This method computes a hash code by summing the ASCII values of each character in the string and taking the modulus with the size of an array.
Syntax
static int HashFunction(string s, string[] array);
Example:
C#
using System;
namespace HashFunctionExample {
class Program {
static void Main(string[] args) {
string input = "Hello, Geeks!";
string[] values = new string[50];
int hashCode = HashFunction(input, values);
values[hashCode] = input;
Console.WriteLine("Hash Code using ASCII Values: {0}", hashCode);
}
static int HashFunction(string s, string[] array) {
int total = 0;
char[] c = s.ToCharArray();
for (int k = 0; k < c.Length; k++)
total += (int)c[k];
return total % array.Length;
}
}
}
OutputHash Code using ASCII Values: 4
Hash Function Using Horner’s Rule
This method creates a polynomial hash function using Horner’s Rule to reduce the likelihood of collisions.
Syntax
static int HashFunction2(string s, string[] array);
Example:
C#
using System;
namespace HashFunctionExample {
class Program {
static void Main(string[] args) {
string input = "Hello, Geeks!";
string[] values = new string[50];
int hashCode = HashFunction2(input, values);
values[hashCode] = input;
Console.WriteLine("Hash Code using Horner's Rule: {0}", hashCode);
}
static int HashFunction2(string s, string[] array) {
long total = 0;
char[] c = s.ToCharArray();
for (int k = 0; k < c.Length; k++)
total = (31 * total + (int)c[k]) % array.Length;
return (int)total;
}
}
}
OutputHash Code using Horner's Rule: 34
Conclusion
Hash functions are vital for string data handling in C#. The methods demonstrated above provide different ways to generate hash codes, each serving unique purposes. The GetHashCode method is useful for quick hash code generation, while SHA256 and MD5 offer more secure hashing options for data integrity verification. Additionally, using ASCII values and Horner’s Rule provides alternative ways to hash strings for applications that may require custom implementations.
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