refactor: add nullable annotations to improve code safety and clarity

Author: jamesmcroft

src/MADE.Collections/CollectionExtensions.cs

@@ -78,7 +78,7 @@ public static bool Update<T>(this IList<T> collection, T item, Func<T, T, bool>
         ArgumentNullException.ThrowIfNull(item);
         ArgumentNullException.ThrowIfNull(collection);
 
-        T existing = collection.FirstOrDefault(x => predicate.Invoke(x, item));
+        T? existing = collection.FirstOrDefault(x => predicate.Invoke(x, item));
         if (existing == null)
         {
             return false;

src/MADE.Collections/ObjectModel/ObservableItemCollection{T}.cs

@@ -83,12 +83,12 @@ public ObservableItemCollection(List<T> list)
     /// <summary>
     /// Occurs when an item is added, removed, changed, moved, or the entire list is refreshed.
     /// </summary>
-    public override event NotifyCollectionChangedEventHandler CollectionChanged;
+    public override event NotifyCollectionChangedEventHandler? CollectionChanged;
 
     /// <summary>
     /// Occurs when an item's <see cref="INotifyPropertyChanged.PropertyChanged"/> event is invoked.
     /// </summary>
-    public event ObservableItemCollectionPropertyChangedEventHandler ItemPropertyChanged;
+    public event ObservableItemCollectionPropertyChangedEventHandler? ItemPropertyChanged;
 
     /// <summary>
     /// Adds a range of objects to the end of the collection.

src/MADE.Data.Converters/BooleanToStringValueConverter.cs

@@ -14,12 +14,12 @@ public class BooleanToStringValueConverter : IValueConverter<bool, string>
     /// <summary>
     /// Gets or sets the positive/true value.
     /// </summary>
-    public string TrueValue { get; set; }
+    public string TrueValue { get; set; } = string.Empty;
 
     /// <summary>
     /// Gets or sets the negative/false value.
     /// </summary>
-    public string FalseValue { get; set; }
+    public string FalseValue { get; set; } = string.Empty;
 
     /// <summary>
     /// Converts the <paramref name="value">value</paramref> to the <see cref="string"/> type.
@@ -33,7 +33,7 @@ public class BooleanToStringValueConverter : IValueConverter<bool, string>
     /// <returns>
     /// The converted <see cref="string"/> object.
     /// </returns>
-    public string Convert(bool value, object parameter = default)
+    public string Convert(bool value, object? parameter = default)
     {
         return value.ToFormattedString(this.TrueValue, this.FalseValue);
     }
@@ -50,7 +50,7 @@ public string Convert(bool value, object parameter = default)
     /// <returns>
     /// The converted <see cref="bool"/> object.
     /// </returns>
-    public bool ConvertBack(string value, object parameter = default)
+    public bool ConvertBack(string value, object? parameter = default)
     {
         if (value == this.TrueValue)
         {

src/MADE.Data.Converters/DateTimeToStringValueConverter.cs

@@ -23,7 +23,7 @@ public class DateTimeToStringValueConverter : IValueConverter<DateTime, string>
     /// <returns>
     /// The converted <see cref="string"/> object.
     /// </returns>
-    public string Convert(DateTime value, object parameter = default)
+    public string Convert(DateTime value, object? parameter = default)
     {
         string format = parameter?.ToString();
         return !string.IsNullOrWhiteSpace(format)
@@ -43,7 +43,7 @@ public string Convert(DateTime value, object parameter = default)
     /// <returns>
     /// The converted <see cref="DateTime"/> object.
     /// </returns>
-    public DateTime ConvertBack(string value, object parameter = default)
+    public DateTime ConvertBack(string value, object? parameter = default)
     {
         if (string.IsNullOrWhiteSpace(value))
         {

src/MADE.Data.Converters/IValueConverter.cs

@@ -26,7 +26,7 @@ public interface IValueConverter<TFrom, TTo>
     /// <returns>
     /// The converted <typeparamref name="TTo"/> object.
     /// </returns>
-    TTo Convert(TFrom value, object parameter = default);
+    TTo Convert(TFrom value, object? parameter = default);
 
     /// <summary>
     /// Converts the <paramref name="value">value</paramref> back to the <typeparamref name="TFrom"/> type.
@@ -40,5 +40,5 @@ public interface IValueConverter<TFrom, TTo>
     /// <returns>
     /// The converted <typeparamref name="TFrom"/> object.
     /// </returns>
-    TFrom ConvertBack(TTo value, object parameter = default);
+    TFrom ConvertBack(TTo value, object? parameter = default);
 }

src/MADE.Data.Converters/StringToBase64StringValueConverter.cs

@@ -23,7 +23,7 @@ public partial class StringToBase64StringValueConverter : IValueConverter<string
     /// <returns>
     /// The converted Base64 <see cref="string"/> object.
     /// </returns>
-    public string Convert(string value, object parameter = default)
+    public string Convert(string value, object? parameter = default)
     {
         return value.ToBase64(parameter as Encoding ?? Encoding.UTF8);
     }
@@ -40,7 +40,7 @@ public string Convert(string value, object parameter = default)
     /// <returns>
     /// The converted <see cref="string"/> object.
     /// </returns>
-    public string ConvertBack(string value, object parameter = default)
+    public string ConvertBack(string value, object? parameter = default)
     {
         return value.FromBase64(parameter as Encoding ?? Encoding.UTF8);
     }

src/MADE.Data.Validation.FluentValidation/FluentValidatorCollection{T}.cs

@@ -40,7 +40,7 @@ public FluentValidatorCollection(int capacity)
     /// <summary>
     /// Occurs when the input value is validated against the collection of validators.
     /// </summary>
-    public event InputValidatedEventHandler Validated;
+    public event InputValidatedEventHandler? Validated;
 
     /// <summary>
     /// Gets or sets a value indicating whether the data provided is in an invalid state.

src/MADE.Data.Validation/ValidatorCollection.cs

@@ -38,7 +38,7 @@ public ValidatorCollection(int capacity)
     /// <summary>
     /// Occurs when the input value is validated against the collection of validators.
     /// </summary>
-    public event InputValidatedEventHandler Validated;
+    public event InputValidatedEventHandler? Validated;
 
     /// <summary>
     /// Gets or sets a value indicating whether the data provided is in an invalid state.

src/MADE.Data.Validation/Validators/AlphaNumericValidator.cs

@@ -11,7 +11,7 @@ namespace MADE.Data.Validation.Validators;
 /// </summary>
 public class AlphaNumericValidator : RegexValidator
 {
-    private string feedbackMessage;
+    private string feedbackMessage = string.Empty;
 
     /// <summary>
     /// Initializes a new instance of the <see cref="AlphaNumericValidator"/> class with the expected RegEx pattern.

src/MADE.Data.Validation/Validators/AlphaValidator.cs

@@ -11,7 +11,7 @@ namespace MADE.Data.Validation.Validators;
 /// </summary>
 public class AlphaValidator : RegexValidator
 {
-    private string feedbackMessage;
+    private string feedbackMessage = string.Empty;
 
     /// <summary>
     /// Initializes a new instance of the <see cref="AlphaValidator"/> class with the expected RegEx pattern.