Obsoleted exceptions that shouldn't be used anymore or be refactored

src/Umbraco.Core/Collections/ObservableDictionary.cs

@@ -242,6 +242,7 @@ namespace Umbraco.Core.Collections
         /// <seealso cref="System.Collections.ObjectModel.ObservableCollection{TValue}" />
         /// <seealso cref="System.Collections.Generic.IReadOnlyDictionary{TKey, TValue}" />
         /// <seealso cref="System.Collections.Generic.IDictionary{TKey, TValue}" />
+        [Obsolete("Throw an ArgumentException when trying to add a duplicate key instead.")]
         [Serializable]
         internal class DuplicateKeyException : Exception
         {

src/Umbraco.Core/Exceptions/ArgumentNullOrEmptyException.cs

@@ -7,6 +7,7 @@ namespace Umbraco.Core.Exceptions
     /// The exception that is thrown when a null reference, or an empty argument, is passed to a method that does not accept it as a valid argument.
     /// </summary>
     /// <seealso cref="System.ArgumentNullException" />
+    [Obsolete("Throw an ArgumentNullException when the parameter is null or an ArgumentException when its empty instead.")]
     [Serializable]
     public class ArgumentNullOrEmptyException : ArgumentNullException
     {

src/Umbraco.Core/Exceptions/DataOperationException.cs

@@ -8,6 +8,7 @@ namespace Umbraco.Core.Exceptions
     /// </summary>
     /// <typeparam name="T"></typeparam>
     /// <seealso cref="System.Exception" />
+    [Obsolete("Refactor the generic type to a concrete serializable type.")]
     [Serializable]
     internal class DataOperationException<T> : Exception
     {

src/Umbraco.Core/Exceptions/WontImplementException.cs

@@ -14,6 +14,7 @@ namespace Umbraco.Core.Exceptions
     /// </remarks>
     /// <seealso cref="System.NotImplementedException" />
     [Serializable]
+    [Obsolete("If a method or operation is not, and will not be, implemented, it is invalid, so we should throw an InvalidOperationException instead.")]
     public class WontImplementException : NotImplementedException
     {
         /// <summary>

src/Umbraco.Core/IO/FileSecurityException.cs

@@ -7,6 +7,7 @@ namespace Umbraco.Core.IO
     /// The exception that is thrown when the caller does not have the required permission to access a file.
     /// </summary>
     /// <seealso cref="System.Exception" />
+    [Obsolete("Throw an UnauthorizedAccessException instead.")]
     [Serializable]
     public class FileSecurityException : Exception
     {

src/Umbraco.Core/Persistence/EntityNotFoundException.cs

@@ -9,6 +9,7 @@ namespace Umbraco.Core.Persistence
     /// An exception used to indicate that an Umbraco entity could not be found.
     /// </summary>
     /// <seealso cref="System.Exception" />
+    [Obsolete("Instead of throwing an exception, return null or an HTTP 404 status code instead.")]
     [Serializable]
     public class EntityNotFoundException : Exception
     {

src/Umbraco.Web/Install/InstallException.cs

@@ -7,6 +7,7 @@ namespace Umbraco.Web.Install
     /// Used for steps to be able to return a JSON structure back to the UI.
     /// </summary>
     /// <seealso cref="System.Exception" />
+    [Obsolete("Refactor the view model into a concrete serializable type.")]
     [Serializable]
     internal class InstallException : Exception
     {