How to get the hash code of a string in C# (2024)

FAQs

How to get the hash code of a string in C#? ›

Getting the hash code of a string is simple in C#. We use the GetHashCode() method. A hash code is a uniquely identified numerical value. Note that strings that have the same value have the same hash code.

The hashCode() method returns the hash code of a string. where s[i] is the ith character of the string, n is the length of the string, and ^ indicates exponentiation.

hashCode() method of String class can be used to convert a string into hash code. hashCode() method will return either negative or positive integer hash values. The returned hash value cannot be re-converted back to string once hashed.

The GetHashCode method provides a hash code for algorithms that need quick checks of object equality. A hash code is a numeric value that is used to insert and identify an object in a hash-based collection, such as the Dictionary<TKey,TValue> class, the Hashtable class, or a type derived from the DictionaryBase class.

Getting the hash code of a string is simple in C#. We use the GetHashCode() method. A hash code is a uniquely identified numerical value. Note that strings that have the same value have the same hash code.

Example. The hash of string S = “cat” can be calculated as: hash(S) = ('c' - 'a') + ('a' - 'a') * 31 + ('c' - 'a') * 31^2. Here, P = 31 as all the characters are in lowercase, so the count of all distinct lowercase characters is 26, and 31 is the prime number and greater than 26.

The hash code for a String object is computed as s [ 0 ] ∗ 31 n − 1 + s [ 1 ] ∗ 31 n − 2 + . . . + s [ n − 1 ] using int arithmetic, where s[i] is the i th character of the string, and n is the length of the string. (The hash value of the empty string is zero.)”

You cannot. it is impossible. That's actually the point of hashes like this. They are a one way hash.

If two string objects are equal, the GetHashCode method returns identical values. However, there is not a unique hash code value for each unique string value. Different strings can return the same hash code. The hash code itself is not guaranteed to be stable.

How to convert string to SHA256 in C#? ›

Cryptography; using System. Text; public class Program { public static void Main() { string source = "Hello World!"; using (SHA256 sha256Hash = SHA256. Create()) { string hash = GetHash(sha256Hash, source); Console. WriteLine($"The SHA256 hash of {source} is: {hash}."); Console.

A HashSet is an optimized collection of unordered, unique elements that provides fast lookups and high-performance set operations. The HashSet class was first introduced in . NET 3.5 and is part of the System. Collection. Generic namespace.

Aside from preprocessor directives, the hash symbol (#) is also used to specify attribute targets in C#. Attributes provide metadata about code, which can be used for various purposes, such as debugging, optimization, and documentation.

Hash functions are fundamental to modern cryptography. These functions map binary strings of an arbitrary length to small binary strings of a fixed length, known as hash values. A cryptographic hash function has the property that it is computationally infeasible to find two distinct inputs that hash to the same value.

The hashcode returned is computed by exclusive-or operation on the hashcodes for the method's declaring class name and the method's name. The hashcode is always the same if the object doesn't change. Hashcode is a unique code generated by the JVM at time of object creation.

The hashCode() method of Java String is the method of the object class that is the parent class of all the classes in Java. The string class also inherits the object class. That's why it is available in the String class. The hashCode is used for the comparison of String objects.