How to sort a list with multiple parameters using CompareTo

Question

hello... i have made a list of students, which contains name, age, grade and an annotation...

some of students has same name or some has same grade or some has same age...

 

when i run the program, it complains that the object is already exits...

my CompareTo method is as follow

 

public int CompareTo(Student other)

{

// If other is not a student

if (other == null)

{

throw new NotImplementedException();

throw new ArgumentException("Other is not a student");

}

// The comparison depends on the comparison of

// the underlying grade, age or name.

else if (this._name.CompareTo(other._name) > 1)

return other.OrderBy(s => s._name).ThenBy(s => s._age);

//return this._age.CompareTo(other._age);

else

return this._name.CompareTo(other._name);

}

 

it doesnt recognize OrderBy... 

 i appreciate any help... regards