Use ArgumentNullException.ThrowIfNull helper method

Did a simple search/replace on the whole repo (except the RSSDP project)
This reduces LOC and should improve performance (methods containing a throw statement don't get inlined)

```
if \((\w+) == null\)
\s+\{
\s+throw new ArgumentNullException\((.*)\);
\s+\}
```

```
ArgumentNullException.ThrowIfNull($1);
```

5 files changed, 15 insertions, 60 deletions

diff --git a/MediaBrowser.Controller/Entities/AggregateFolder.cs b/MediaBrowser.Controller/Entities/AggregateFolder.cs
index 77a857b785..e671e5c711 100644
--- a/MediaBrowser.Controller/Entities/AggregateFolder.cs
+++ b/MediaBrowser.Controller/Entities/AggregateFolder.cs
@@ -171,10 +171,7 @@ namespace MediaBrowser.Controller.Entities
         /// <exception cref="ArgumentNullException">Throws if child is null.</exception>
         public void AddVirtualChild(BaseItem child)
         {
-            if (child == null)
-            {
-                throw new ArgumentNullException(nameof(child));
-            }
+            ArgumentNullException.ThrowIfNull(child);
 
             _virtualChildren.Add(child);
         }
diff --git a/MediaBrowser.Controller/Entities/BaseItem.cs b/MediaBrowser.Controller/Entities/BaseItem.cs
index 9461b01e31..41fce67fa7 100644
--- a/MediaBrowser.Controller/Entities/BaseItem.cs
+++ b/MediaBrowser.Controller/Entities/BaseItem.cs
@@ -1101,10 +1101,7 @@ namespace MediaBrowser.Controller.Entities
 
         private MediaSourceInfo GetVersionInfo(bool enablePathSubstitution, BaseItem item, MediaSourceType type)
         {
-            if (item == null)
-            {
-                throw new ArgumentNullException(nameof(item));
-            }
+            ArgumentNullException.ThrowIfNull(item);
 
             var protocol = item.PathProtocol;
 
@@ -1544,10 +1541,7 @@ namespace MediaBrowser.Controller.Entities
         /// <exception cref="ArgumentNullException">If user is null.</exception>
         public bool IsParentalAllowed(User user)
         {
-            if (user == null)
-            {
-                throw new ArgumentNullException(nameof(user));
-            }
+            ArgumentNullException.ThrowIfNull(user);
 
             if (!IsVisibleViaTags(user))
             {
@@ -1667,10 +1661,7 @@ namespace MediaBrowser.Controller.Entities
         /// <exception cref="ArgumentNullException"><paramref name="user" /> is <c>null</c>.</exception>
         public virtual bool IsVisible(User user)
         {
-            if (user == null)
-            {
-                throw new ArgumentNullException(nameof(user));
-            }
+            ArgumentNullException.ThrowIfNull(user);
 
             return IsParentalAllowed(user);
         }
@@ -1842,10 +1833,7 @@ namespace MediaBrowser.Controller.Entities
             DateTime? datePlayed,
             bool resetPosition)
         {
-            if (user == null)
-            {
-                throw new ArgumentNullException(nameof(user));
-            }
+            ArgumentNullException.ThrowIfNull(user);
 
             var data = UserDataManager.GetUserData(user, this);
 
@@ -1876,10 +1864,7 @@ namespace MediaBrowser.Controller.Entities
         /// <exception cref="ArgumentNullException">Throws if user is null.</exception>
         public virtual void MarkUnplayed(User user)
         {
-            if (user == null)
-            {
-                throw new ArgumentNullException(nameof(user));
-            }
+            ArgumentNullException.ThrowIfNull(user);
 
             var data = UserDataManager.GetUserData(user, this);
 
@@ -2110,10 +2095,7 @@ namespace MediaBrowser.Controller.Entities
         /// <returns>Image index.</returns>
         public int GetImageIndex(ItemImageInfo image)
         {
-            if (image == null)
-            {
-                throw new ArgumentNullException(nameof(image));
-            }
+            ArgumentNullException.ThrowIfNull(image);
 
             if (image.Type == ImageType.Chapter)
             {
@@ -2320,10 +2302,7 @@ namespace MediaBrowser.Controller.Entities
 
         public virtual bool IsUnplayed(User user)
         {
-            if (user == null)
-            {
-                throw new ArgumentNullException(nameof(user));
-            }
+            ArgumentNullException.ThrowIfNull(user);
 
             var userdata = UserDataManager.GetUserData(user, this);
 
diff --git a/MediaBrowser.Controller/Entities/BaseItemExtensions.cs b/MediaBrowser.Controller/Entities/BaseItemExtensions.cs
index e0583e6308..948eb43754 100644
--- a/MediaBrowser.Controller/Entities/BaseItemExtensions.cs
+++ b/MediaBrowser.Controller/Entities/BaseItemExtensions.cs
@@ -71,15 +71,9 @@ namespace MediaBrowser.Controller.Entities
             where T : BaseItem
             where TU : BaseItem
         {
-            if (source == null)
-            {
-                throw new ArgumentNullException(nameof(source));
-            }
+            ArgumentNullException.ThrowIfNull(source);
 
-            if (dest == null)
-            {
-                throw new ArgumentNullException(nameof(dest));
-            }
+            ArgumentNullException.ThrowIfNull(dest);
 
             var destProps = typeof(TU).GetProperties().Where(x => x.CanWrite).ToList();
 
diff --git a/MediaBrowser.Controller/Entities/Folder.cs b/MediaBrowser.Controller/Entities/Folder.cs
index 92d12a86ca..808f918104 100644
--- a/MediaBrowser.Controller/Entities/Folder.cs
+++ b/MediaBrowser.Controller/Entities/Folder.cs
@@ -1023,10 +1023,7 @@ namespace MediaBrowser.Controller.Entities
             IServerConfigurationManager configurationManager,
             ICollectionManager collectionManager)
         {
-            if (items == null)
-            {
-                throw new ArgumentNullException(nameof(items));
-            }
+            ArgumentNullException.ThrowIfNull(items);
 
             if (CollapseBoxSetItems(query, queryParent, user, configurationManager))
             {
@@ -1273,20 +1270,14 @@ namespace MediaBrowser.Controller.Entities
 
         public List<BaseItem> GetChildren(User user, bool includeLinkedChildren)
         {
-            if (user == null)
-            {
-                throw new ArgumentNullException(nameof(user));
-            }
+            ArgumentNullException.ThrowIfNull(user);
 
             return GetChildren(user, includeLinkedChildren, null);
         }
 
         public virtual List<BaseItem> GetChildren(User user, bool includeLinkedChildren, InternalItemsQuery query)
         {
-            if (user == null)
-            {
-                throw new ArgumentNullException(nameof(user));
-            }
+            ArgumentNullException.ThrowIfNull(user);
 
             // the true root should return our users root folder children
             if (IsPhysicalRoot)
@@ -1367,10 +1358,7 @@ namespace MediaBrowser.Controller.Entities
 
         public virtual IEnumerable<BaseItem> GetRecursiveChildren(User user, InternalItemsQuery query)
         {
-            if (user == null)
-            {
-                throw new ArgumentNullException(nameof(user));
-            }
+            ArgumentNullException.ThrowIfNull(user);
 
             var result = new Dictionary<Guid, BaseItem>();
 
diff --git a/MediaBrowser.Controller/Entities/PeopleHelper.cs b/MediaBrowser.Controller/Entities/PeopleHelper.cs
index 687ce1ec8d..8571bfcea5 100644
--- a/MediaBrowser.Controller/Entities/PeopleHelper.cs
+++ b/MediaBrowser.Controller/Entities/PeopleHelper.cs
@@ -11,10 +11,7 @@ namespace MediaBrowser.Controller.Entities
     {
         public static void AddPerson(List<PersonInfo> people, PersonInfo person)
         {
-            if (person == null)
-            {
-                throw new ArgumentNullException(nameof(person));
-            }
+            ArgumentNullException.ThrowIfNull(person);
 
             if (string.IsNullOrEmpty(person.Name))
             {