Redundant comparison & "if" before assignment

Question

Here is the example: if(value != ageValue) { ageValue = value; } I mean, if we assign the value of a variable to another one, why would we need to check if they have anyway the same value? That confuses me. Here is the broader context: private double ageValue; public double Age { get { return ageValue; } set { if(value != ageValue) { ageValue = value; } } } JavaScript questions and answers, JavaScript questions pdf, JavaScript question bank, JavaScript questions and answers pdf, mcq on JavaScript pdf, JavaScript questions and solutions, JavaScript mcq Test , Interview JavaScript questions, JavaScript Questions for Interview, JavaScript MCQ (Multiple Choice Questions)

Answer 1

Here is a code sample when the check is quite useful: public class MyClass { ... int ageValue = 0; public int AgeValue { get { return ageValue } protected set { ... // value validation here // your code starts if (value != ageValue) { ageValue = value; } // your code ends else return; // do nothing since value == ageValue // ageValue has been changed // Time (or / and memory) consuming process SaveToRDBMS(); InvalidateCache(); ... } } ... More natural implementation, however, is to check in the very beginning in order to avoid unnecessary computation. protected set { if (ageValue == value) return; ... // value validation here ageValue = value; // ageValue has been changed // Time (or / and memory) consuming process SaveToRDBMS(); InvalidateCache(); ... }