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Why do I need to implement GetHashCode?
For value types, GetHashCode() provides a default hash code implementation that uses reflection. You should consider overriding it for better performance. A hash function must have the following properties: If two objects compare as equal, the GetHashCode() method for each object must return the same value.
What is Hashcode algorithm?
The hashCode method is an inbuilt method that returns the integer hashed value of the input value. If two or more objects are equal according to the equals method, then their hashes should be equal too. If two or more objects are not equal according to the equals method, then their hashes can be equal or unequal.
Why is 31 used in hashCode?
The value 31 was chosen because it is an odd prime. If it were even and the multiplication overflowed, information would be lost, as multiplication by 2 is equivalent to shifting. The advantage of using a prime is less clear, but it is traditional.
Which is better equals or == in C#?
This article explains the basic difference between these two. The Equality Operator ( ==) is the comparison operator and the Equals() method compares the contents of a string. The == Operator compares the reference identity while the Equals() method compares only contents.
What does |= mean in C#?
What does |= (single pipe equal) and &=(single ampersand equal) mean.
When does gethashcode return the same hash code?
The GetHashCode method for an object must consistently return the same hash code as long as there is no modification to the object state that determines the return value of the object’s Equals method.
Can a derived type override the gethashcode method?
The GetHashCode method can be overridden by a derived type. If GetHashCode is not overridden, hash codes for reference types are computed by calling the Object.GetHashCode method of the base class, which computes a hash code based on an object’s reference; for more information, see RuntimeHelpers.GetHashCode.
What are the properties of a hash function?
A hash function must have the following properties: – If two objects compare as equal, the GetHashCode () method for each object must return the same value. However, if two objects do not compare as equal, the GetHashCode () methods for the two objects do not have to return different values.
When to delegate to the base class gethashcode ( ) method?
For classes derived from Object, the GetHashCode method can delegate to the base class GetHashCode () implementation only if the derived class defines equality to be reference equality. The default implementation of GetHashCode () for reference types returns a hash code that is equivalent to the one returned by the GetHashCode (Object) method.