Why is '397' used for ReSharper GetHashCode override?
HashResharperHash Code-UniquenessHash Problem Overview
Like many of you, I use ReSharper to speed up the development process. When you use it to override the equality members of a class, the code-gen it produces for GetHashCode()
looks like:
public override int GetHashCode()
{
unchecked
{
int result = (Key != null ? Key.GetHashCode() : 0);
result = (result * 397) ^ (EditableProperty != null ? EditableProperty.GetHashCode() : 0);
result = (result * 397) ^ ObjectId;
return result;
}
}
Of course I have some of my own members in there, but what I am wanting to know is why 397?
- EDIT: So my question would be better worded as, is there something 'special' about the 397 prime number outside of it being a prime number?
Hash Solutions
Solution 1 - Hash
Probably because 397 is a prime of sufficient size to cause the result variable to overflow and mix the bits of the hash somewhat, providing a better distribution of hash codes. There's nothing particularly special about 397 that distinguishes it from other primes of the same magnitude.