Retreive the Width Delta of a ContentSizeFitter game object

Here is a screenshot of my project organisation. My List Container object is a basic RectTransform of width 1000. My object List Grid contains a Content Size Fitter component, using "Horizontal Fit : Preferred Size".

When my project is run, I would like to retreive the value for the W Delta field (in this case, -170). So far, I've tried displaying the following data, using the Debug.Log() method from the List Grid game object :

• GetComponent(RectTransform).rect.width

  • displays "1000"

• GetComponent(RectTransform).sizeDelta

  • displays "(0.0, 0.0)"

• GetComponent(RectTransform).rect.size

  • displays "(1000.0, 570.0)"

• GetComponent(RectTransform).rect.xMax

  • displays "1000"

In all cases, the value displayed is either 0 or the width of my List Container. What is the correct way to retrieve the W Delta field ?