updated README and code format

Assets/Scenes/ImageTracking/ImageTrackingWithMultiplePrefabs/DynamicPrefab.cs

 using System;
 using System.Text;
 using UnityEngine;
-
 using UnityEngine.XR.ARFoundation;
 using UnityEngine.XR.ARSubsystems;
 
             switch (m_State)
             {
                 case State.OriginalPrefab:
+                {
+                    if (GUILayout.Button($"Alternative Prefab for {GetComponent<PrefabImagePairManager>().imageLibrary[0].name}"))
-                        if (GUILayout.Button($"Alternative Prefab for {GetComponent<PrefabImagePairManager>().imageLibrary[0].name}"))
-                        {
-                            m_State = State.ChangeToAlternativePrefab;
-                        }
-                        break;
+                        m_State = State.ChangeToAlternativePrefab;
+
+                    break;
+                }
+                {
+                    if (GUILayout.Button($"Original Prefab for {GetComponent<PrefabImagePairManager>().imageLibrary[0].name}"))
-                        if (GUILayout.Button($"Original Prefab for {GetComponent<PrefabImagePairManager>().imageLibrary[0].name}"))
-                        {
-                            m_State = State.ChangeToOriginalPrefab;
-                        }
-                        break;
+                        m_State = State.ChangeToOriginalPrefab;
+
+                    break;
+                }
-                    {
-                        GUILayout.Label(m_ErrorMessage);
-                        break;
-                    }
+                {
+                    GUILayout.Label(m_ErrorMessage);
+                    break;
+                }
-
             GUILayout.EndArea();
         }
 
             switch (m_State)
             {
                 case State.ChangeToAlternativePrefab:
+                {
+                    if (!alternativePrefab)
-                        if (!alternativePrefab)
-                        {
-                            SetError("No alternative prefab is given.");
-                            break;
-                        }
+                        SetError("No alternative prefab is given.");
+                        break;
+                    }
+
+                    var manager = GetComponent<PrefabImagePairManager>();
+                    if (!manager)
+                    {
+                        SetError($"No {nameof(PrefabImagePairManager)} available.");
+                        break;
+                    }
-                        var manager = GetComponent<PrefabImagePairManager>();
-                        if (!manager)
-                        {
-                            SetError($"No {nameof(PrefabImagePairManager)} available.");
-                            break;
-                        }
+                    var library = manager.imageLibrary;
+                    if (!library)
+                    {
+                        SetError($"No image library available.");
+                        break;
+                    }
-                        var library = manager.imageLibrary;
-                        if (!library)
-                        {
-                            SetError($"No image library available.");
-                            break;
-                        }
+                    if (!m_OriginalPrefab)
+                        m_OriginalPrefab = manager.GetPrefabForReferenceImage(library[0]);
-                        if (!m_OriginalPrefab)
-                            m_OriginalPrefab = manager.GetPrefabForReferenceImage(library[0]);
+                    manager.SetPrefabForReferenceImage(library[0], alternativePrefab);
+                    m_State = State.AlternativePrefab;
+                    break;
+                }
-                        manager.SetPrefabForReferenceImage(library[0], alternativePrefab);
-                        m_State = State.AlternativePrefab;
+                case State.ChangeToOriginalPrefab:
+                {
+                    if (!m_OriginalPrefab)
+                    {
+                        SetError("No original prefab is given.");
-                case State.ChangeToOriginalPrefab:
+                    var manager = GetComponent<PrefabImagePairManager>();
+                    if (!manager)
-                        if (!m_OriginalPrefab)
-                        {
-                            SetError("No original prefab is given.");
-                            break;
-                        }
+                        SetError($"No {nameof(PrefabImagePairManager)} available.");
+                        break;
+                    }
-                        var manager = GetComponent<PrefabImagePairManager>();
-                        if (!manager)
-                        {
-                            SetError($"No {nameof(PrefabImagePairManager)} available.");
-                            break;
-                        }
-
-                        var library = manager.imageLibrary;
-                        if (!library)
-                        {
-                            SetError($"No image library available.");
-                            break;
-                        }
-
-                        manager.SetPrefabForReferenceImage(library[0], m_OriginalPrefab);
-                        m_State = State.OriginalPrefab;
+                    var library = manager.imageLibrary;
+                    if (!library)
+                    {
+                        SetError($"No image library available.");
+                    manager.SetPrefabForReferenceImage(library[0], m_OriginalPrefab);
+                    m_State = State.OriginalPrefab;
+                    break;
+                }
             }
         }
     }

Assets/Scenes/ImageTracking/ImageTrackingWithMultiplePrefabs/PrefabImagePairManager.cs

 
         void AssignPrefab(ARTrackedImage trackedImage)
         {
-            if (m_PrefabsDictionary.TryGetValue(trackedImage.referenceImage.guid, out GameObject prefab))
+            if (m_PrefabsDictionary.TryGetValue(trackedImage.referenceImage.guid, out var prefab))
                 m_Instantiated[trackedImage.referenceImage.guid] = Instantiate(prefab, trackedImage.transform);
         }
 
         public void SetPrefabForReferenceImage(XRReferenceImage referenceImage, GameObject alternativePrefab)
         {
             m_PrefabsDictionary[referenceImage.guid] = alternativePrefab;
-            if (m_Instantiated.TryGetValue(referenceImage.guid, out GameObject instantiatedPrefab))
+            if (m_Instantiated.TryGetValue(referenceImage.guid, out var instantiatedPrefab))
             {
                 m_Instantiated[referenceImage.guid] = Instantiate(alternativePrefab, instantiatedPrefab.transform.parent);
                 Destroy(instantiatedPrefab);

README.md

 
 ## ImageTracking
 
-There are two samples demonstrating image tracking. Basic and Multi Image tracking are supported on ARCore, ARKit, and Magic Leap. To enable image tracking, you must first create an `XRReferenceImageLibrary`. This is the set of images to look for in the environment. [Click here](https://docs.unity3d.com/Packages/com.unity.xr.arsubsystems@4.1/manual/image-tracking.html) for instructions on creating one.
+There are two samples demonstrating image tracking. The image tracking samples are supported on ARCore, ARKit, and Magic Leap. To enable image tracking, you must first create an `XRReferenceImageLibrary`. This is the set of images to look for in the environment. [Click here](https://docs.unity3d.com/Packages/com.unity.xr.arsubsystems@4.1/manual/image-tracking.html) for instructions on creating one.
 
 You can also add images to the reference image library at runtime. This sample includes a button that adds the images `one.png` and `two.png` to the reference image library. See the script `DynamicLibrary.cs` for example code.
 
 
 With [`PrefabImagePairManager.cs`](https://github.com/Unity-Technologies/arfoundation-samples/blob/master/Assets/Scenes/ImageTracking/ImageTrackingWithMultiplePrefabs/PrefabImagePairManager.cs) script, you can assign different prefabs for each image in the reference image library.
 
-You can also change prefabs at runtime. This sample includes a button that switch between the original and alternative prefab for the first image in the reference image library. See the script `DynamicPrefab.cs` for example code.
+You can also change prefabs at runtime. This sample includes a button that switch between the original and alternative prefab for the first image in the reference image library. See the script [`DynamicPrefab.cs`](https://github.com/Unity-Technologies/arfoundation-samples/blob/master/Assets/Scenes/ImageTracking/ImageTrackingWithMultiplePrefabs/DynamicPrefab.cs) for example code.
 ## ObjectTracking
 
 Similar to the image tracking sample, this sample detects a 3D object from a set of reference objects in an `XRReferenceObjectLibrary`. [Click here](https://docs.unity3d.com/Packages/com.unity.xr.arsubsystems@4.1/manual/object-tracking.html) for instructions on creating one.
 
 ## Contributions and Pull Requests
 
-We are not accepting pull requests at this time. If you find an issue with the samples, our would like to request a new sample, please [submit a GitHub issue](https://github.com/Unity-Technologies/arfoundation-samples/issues).
+We are not accepting pull requests at this time. If you find an issue with the samples, or would like to request a new sample, please [submit a GitHub issue](https://github.com/Unity-Technologies/arfoundation-samples/issues).

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