Unique HashCode Generation for Unique object using C#

Question

I want to generate the hash code for a object and store the generated hash code into the database. After some time I want to update the the object.Before updating the object, I want to check whether the object is changed or not using hash code. if the Generated has code and stored has codes are same I want to skip the updation, else I will update the Object. How can I implement this?

Answer 1

You can use xor to include all the relevant properties' hash codes.

void Main() {
    var emp = new Employee {
        Id = 123,
        FirstName = "Billy",
        LastName = "Bobby", // lol, it's actually two first names
    };

    int originalHash = emp.GetHashCode();

    emp.FirstName = "Timmy";

    Console.WriteLine ("Original: {0}, Current: {1}", originalHash, emp.GetHashCode());
}

class Employee {
    public long Id { get; set; }
    public string FirstName { get; set; }
    public string LastName { get; set; }

    public override int GetHashCode() {
        return this.Id.GetHashCode()
            ^ this.FirstName.GetHashCode()
            ^ this.LastName.GetHashCode();
    }

    public override bool Equals(object other) {
        var otherEmployee = other as Employee;
        return otherEmployee != null
            && otherEmployee.Id == this.Id
            && otherEmployee.FirstName == this.FirstName
            && otherEmployee.LastName == this.FirstName;
    }
}