LINQ – Does the Where expression return new instance or reference to object instance

The instances are the same if they are classes, but copies if they are structs/value types.

int, byte and double are value types, as are structs (like System.Drawing.Point and self-defined structs).
But strings, all of your own classes, basically “the rest”, are reference types.

Note: LINQ uses the same rules as all other assignments.

For objects:

Person p1 = new Person();
p1.Name = "Mr Jones";
Person p2 = p1;
p2.Name = "Mr Anderssen";
// Now p1.Name is also "Mr Anderssen"

For structs:

Point p1 = new Point();
p1.x = 5;
Point p2 = p1;
p2.x = 10;
// p1.x is still 5

The same rules apply when using LINQ.