From bd577975b2d5d53c5c90de8f1d5d181930b5dd08 Mon Sep 17 00:00:00 2001
From: TheXamlGuy <dan_clark@outlook.com>
Date: Fri, 27 Sep 2024 19:55:45 +0100
Subject: [PATCH] Allow validation to be looked up by name

---
 .../IReadOnlyIndexDictionary.cs               | 10 ++++
 Toolkit.Foundation/IValidation.cs             |  2 +-
 Toolkit.Foundation/ReadOnlyIndexDictionary.cs | 56 +++++++++++++++++++
 Toolkit.Foundation/Validation.cs              |  5 +-
 4 files changed, 70 insertions(+), 3 deletions(-)
 create mode 100644 Toolkit.Foundation/IReadOnlyIndexDictionary.cs
 create mode 100644 Toolkit.Foundation/ReadOnlyIndexDictionary.cs

diff --git a/Toolkit.Foundation/IReadOnlyIndexDictionary.cs b/Toolkit.Foundation/IReadOnlyIndexDictionary.cs
new file mode 100644
index 0000000..3b7a0f2
--- /dev/null
+++ b/Toolkit.Foundation/IReadOnlyIndexDictionary.cs
@@ -0,0 +1,10 @@
+
+namespace Toolkit.Foundation
+{
+    public interface IReadOnlyIndexDictionary<TKey, TValue> : 
+        IReadOnlyDictionary<TKey, TValue>
+        where TKey : notnull
+    {
+        KeyValuePair<TKey, TValue> this[int index] { get; }
+    }
+}
\ No newline at end of file
diff --git a/Toolkit.Foundation/IValidation.cs b/Toolkit.Foundation/IValidation.cs
index fc8d8ab..94cb1e8 100644
--- a/Toolkit.Foundation/IValidation.cs
+++ b/Toolkit.Foundation/IValidation.cs
@@ -6,7 +6,7 @@ namespace Toolkit.Foundation;
 public interface IValidation :
     INotifyPropertyChanged
 {
-    IReadOnlyDictionary<string, string> Errors { get; }
+    IReadOnlyIndexDictionary<string, string> Errors { get; }
 
     bool HasErrors { get; }
 
diff --git a/Toolkit.Foundation/ReadOnlyIndexDictionary.cs b/Toolkit.Foundation/ReadOnlyIndexDictionary.cs
new file mode 100644
index 0000000..f88c555
--- /dev/null
+++ b/Toolkit.Foundation/ReadOnlyIndexDictionary.cs
@@ -0,0 +1,56 @@
+using System.Collections;
+using System.Diagnostics.CodeAnalysis;
+
+namespace Toolkit.Foundation;
+
+public class ReadOnlyIndexDictionary<TKey, TValue> :
+    IReadOnlyDictionary<TKey, TValue>, 
+    IReadOnlyIndexDictionary<TKey, TValue> 
+    where TKey : notnull
+{
+    private readonly Dictionary<TKey, TValue> dictionary;
+    private readonly List<KeyValuePair<TKey, TValue>> indexedItems;
+
+    public ReadOnlyIndexDictionary(IDictionary<TKey, TValue> items)
+    {
+        dictionary = new Dictionary<TKey, TValue>(items);
+        indexedItems = [.. dictionary];
+    }
+
+    public TValue this[TKey key] =>
+        dictionary[key];
+
+    public KeyValuePair<TKey, TValue> this[int index] =>
+        indexedItems[index];
+
+    public IEnumerable<TKey> Keys =>
+        dictionary.Keys;
+
+    public IEnumerable<TValue> Values =>
+        dictionary.Values;
+
+    public int Count => dictionary.Count;
+
+    public bool ContainsKey(TKey key) =>
+        dictionary.ContainsKey(key);
+
+    public IEnumerator<KeyValuePair<TKey, TValue>> GetEnumerator() =>
+        dictionary.GetEnumerator();
+
+    IEnumerator IEnumerable.GetEnumerator() => dictionary.GetEnumerator();
+
+    public bool TryGetValue(TKey key, [MaybeNullWhen(false)] out TValue value)
+    {
+        if (dictionary.TryGetValue(key, out TValue? localValue))
+        {
+            if (localValue is not null)
+            {
+                value = localValue;
+                return true;
+            }
+        }
+
+        value = default;
+        return false;
+    }
+}
diff --git a/Toolkit.Foundation/Validation.cs b/Toolkit.Foundation/Validation.cs
index c5337c0..778c17e 100644
--- a/Toolkit.Foundation/Validation.cs
+++ b/Toolkit.Foundation/Validation.cs
@@ -10,8 +10,8 @@ public class Validation(IValidatorCollection validators) :
 
     public event PropertyChangedEventHandler? PropertyChanged;
 
-    public IReadOnlyDictionary<string, string> Errors =>
-        errors.AsReadOnly();
+    public IReadOnlyIndexDictionary<string, string> Errors => 
+        new ReadOnlyIndexDictionary<string, string>(errors);
 
     public bool HasErrors =>
         Errors.Count > 0;
@@ -116,6 +116,7 @@ public class Validation(IValidatorCollection validators) :
             OnPropertyChanged(nameof(Errors), null, null);
         }
     }
+
     private string GetPropertyName<T>(Expression<Func<T>> expression)
     {
         return expression.Body switch