In Unity, Transform can be used to control the movement, scaling and rotation of 3d objects. How to set Transform in Canvas? You can use RectTransform, which inherits from Transform.

//    RectTransform a = this. Transform. Getcomponent < RectTransform > (); / / get the RectTransform by getting the component.
  RectTransform      a = this.transform as RectTransform;//Get RectTransform by as keyword

Move the location of the element: you can't use a.position = new Vector3() directly, which can also be set, but you don't know where to set it. To use the following UI specific parameter settings.

       a.anchoredPosition=new Vector2(10,10);//Set the location of UI elements
       a.anchoredPosition3D = new Vector3(10,10,10);//Set the location of the UI element. The above is 2d, and this is 3d.

Get the properties of UI elements and read them through rect. This parameter is read-only and cannot be set.

 Debug.Log("Width:"+a.rect.width) ;
       Debug.Log("Height:"+a.rect.height) ;
       Debug.Log("Orientation: bottom"+a.rect.bottom+" right: "+a.rect.right); 

Set the width and height of the elements of the UI:

//a.SetSizeWithCurrentAnchors(RectTransform.Axis.Horizontal,300); / / set width
 //a.SetSizeWithCurrentAnchors(RectTransform.Axis.Vertical,100); / / set height

Here is the code I tested.

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class ButtonTransform : MonoBehaviour
{
    // Start is called before the first frame update
    private RectTransform a;
    void Start()
    {
//         A = this. Transform. Getcomponent < recttransform > (); / / get
        a = this.transform as RectTransform;
    }

    // Update is called once per frame
    void Update()
    { 
//        transform.Translate(Vector3.right*Time.deltaTime*50) ;
//        a.anchoredPosition=new Vector2(10,10);
//        a.anchoredPosition3D = new Vector3(10,10,10);
       Debug.Log("Width:"+a.rect.width) ;
       Debug.Log("Height:"+a.rect.height) ;
       Debug.Log("Orientation: bottom"+a.rect.bottom+" right: "+a.rect.right); 
       Debug.Log(a.sizeDelta);  
//        a.SetSizeWithCurrentAnchors(RectTransform.Axis.Horizontal,300);
//        a.SetSizeWithCurrentAnchors(RectTransform.Axis.Vertical,100);

    }
}