How to stop the rotation of an object?

Question

C++ / C#

I have this line of code
this.transform.RotateAround(new Vector3(positionX,positionY,positionZ), new Vector3(0f, 0f, 1f), 360f * Time.deltaTime);
which rotates the object relative to a given point, with a certain speed. And I need the line to rotate by a certain number of degrees. (90)
if (transform.eulerAngles.z == 90) { code }
This option does not work

Answer 1

Quaternion target = Quaternion.Euler (0, 0, 90); 
transform.rotation = Quaternion.RotateTowards (transform.rotation, target, Time.deltaTime * 500);

So try. So I rotated the camera in my game by 90 degrees.