// Add
/*
The Equals(object obj) and GetHashCode() methods in C# are used by .NET Framework for comparing objects and generating hash codes respectively.
- Equals(object obj): This method is called when you compare two objects using the Equals() method. For example, if you have two objects obj1 and obj2 of the Part class, and you call obj1.Equals(obj2), the Equals(object obj)
method in your Part class will be invoked.
- GetHashCode(): This method is used when you use an object as a key in a hash-based collection like HashSet, Dictionary, etc. The .NET Framework uses the hash code returned by this method to quickly look up the object in the collection.
Part part1 = new Part() { PartName = "crank arm", PartId = 1234 };
Part part2 = new Part() { PartName = "crank arm", PartId = 1234 };
bool areEqual = part1.Equals(part2); // This will call the Equals method
Dictionary<Part, string> partsDictionary = new Dictionary<Part, string>();
PS: It's important to override GetHashCode() in a meaningful way when you override Equals(), to ensure that equal objects return the same hash code. This is crucial for the correct operation of hash-based collections.
In your current implementation, you're using the base Object.GetHashCode(), which does not provide this guarantee. A simple improvement would be to return the hash code of PartId, since that's what you're using for equality checks:
public override int GetHashCode()
{
return PartId;
}
Question ) whats the use of public override bool Equals(object obj) vs public bool Equals(Part other)
-The public override bool Equals(object obj) method is overriding the Equals method from the base Object class in .NET. This method is used when you compare an object of type Part with an object of any type. If the other object is not of type Part,
it will return false.in Equals we also use "as keyword".
PS: The as operator is used to perform conversion between compatible reference types or Nullable types. This operator
returns the object when they are compatible with the given type and return null if the conversion is not possible instead of raising an exception. The working of as operator is quite similar to is an operator but in shortening manner.
Syntax:
expression as type
is equal to
expression is type ? (type)expression : (type)null
The above syntax is equivalent to below code. But the expression variable will be evaluated only one time.
On the other hand, public bool Equals(Part other) is an implementation of the IEquatable<Part>.Equals(Part) method. This method is used when you compare a Part object with another Part object. It's more specific than the Equals(object obj) method.
- The IEquatable<T> interface is used to define a generalized method that a value type or class can implement to create a type-specific method for determining equality of instances.The advantage of using IEquatable<T> is that it can provide better
performance than Equals(object obj) because it doesn't require boxing or unboxing operations when used with a value type.
In your code, Equals(object obj) is calling Equals(Part other), so they are working together. If the object is not a Part, it returns false. If it is a Part, it calls Equals(Part other) to determine equality based on PartId.
Question)can you give me an egample where it will call Equals (object obj)
object obj = part2;//see obj is another object
bool areEqual = part1.Equals(obj); // This will call Equals(object obj)
In this example, even though obj is actually a Part, because its compile-time type is object, the Equals(object obj) method is called. Inside this method, obj is cast to Part, and then Equals(Part other) is called.
Here's another example where Equals(object obj) would be called:
string str = "Not a part";
bool areEqual = part1.Equals(str); // This will call Equals(object obj)
*/
//2 -AddRange
// InsertRange , RemoveRange etc always start at index and remember index are always 0 based.
//3 TrimExcess() -
// Sets the capacity to the actual number of elements in the List<T>, if that number is less than a threshold value.
//7 Find
/*In XML (Extensible Markup Language), elements and attributes are fundamental components used to structure data.
Elements:
- Elements are the primary building blocks of an XML document. They are defined by a start tag, an end tag, and the content in between. Elements can contain text, other elements, or both.
- Elements can be nested within other elements, allowing for a hierarchical (tree-like) structure of data.
- An example of an element:
<book>
The Catcher in the Rye
</book>
Attributes:
- Attributes provide additional information about elements. They are always specified in the start tag of an element and are made up of a name-value pair.
- Attributes are used to add properties to elements, such as identifiers, types, or other metadata.
- An example of an element with an attribute:
<book author="J.D. Salinger">
In our eg books.xml , first there are 2 Book elements. Each Book element has an attribute of Id. Then for each Book element, we looks for inner elements and those inner elements are Author Title etc
