Fix Unit Tests (#1036)

* Enable Nullable on Unit Tests

* Enable Nullable on Xamarin.CommunityToolkit.Markup

* Enable Nullable on Xamarin.CommunityToolkit.Sample

* Enable Nullable on Android, GTK, iOS and Tizen Samples

* Enable Nullable for UWP & WPF Sample Projects

* Add Nullability

* Resolve Possible Null References

* Removed Possible Null References

* Update AppResources.Designer.cs

* Handle Nullability

* Updated Nullabiltiy

* Update Converters & Unit Tests

* Resolve MediaSource Unit Tests

* Fix VariableMultiValueConverter

* Fixed ImpliedOrderGridBehavior

* Update NumericValidationBehavior.shared.cs

Author: TheCodeTraveler

src/CommunityToolkit/Xamarin.CommunityToolkit/Behaviors/ImpliedOrderGridBehavior.shared.cs

@@ -11,6 +11,7 @@ namespace Xamarin.CommunityToolkit.Behaviors
 	/// </summary>
 	public class ImpliedOrderGridBehavior : BaseBehavior<Grid>
 	{
+		bool[][]? usedMatrix;
 		int rowCount;
 		int columnCount;
 
@@ -51,21 +52,24 @@ bool[][] InitMatrix()
 			rowCount = View.RowDefinitions.Count;
 			if (rowCount == 0)
 				rowCount = 1;
+
 			columnCount = View.ColumnDefinitions.Count;
 			if (columnCount == 0)
 				columnCount = 1;
+
 			var newMatrix = new bool[rowCount][];
 			for (var r = 0; r < rowCount; r++)
 				newMatrix[r] = new bool[columnCount];
+
 			return newMatrix;
 		}
 
-		void FindNextCell(out int rowIndex, out int columnIndex, out bool[][] matrix)
+		void FindNextCell(out int rowIndex, out int columnIndex)
 		{
-			matrix = InitMatrix();
+			usedMatrix ??= InitMatrix();
 
 			// Find the first available row
-			var row = matrix.FirstOrDefault(r => r.Any(c => !c));
+			var row = usedMatrix.FirstOrDefault(r => r.Any(c => !c));
 
 			// If no row is found, set cell to origin and log
 			if (row == null)
@@ -75,13 +79,13 @@ void FindNextCell(out int rowIndex, out int columnIndex, out bool[][] matrix)
 				columnIndex = Math.Max(columnCount - 1, 0);
 				return;
 			}
-			rowIndex = matrix.IndexOf(row);
+			rowIndex = usedMatrix.IndexOf(row);
 
 			// Find the first available column
 			columnIndex = row.IndexOf(row.FirstOrDefault(c => !c));
 		}
 
-		void UpdateUsedCells(int row, int column, int rowSpan, int columnSpan, bool[][] usedMatrix)
+		void UpdateUsedCells(int row, int column, int rowSpan, int columnSpan)
 		{
 			var rowEnd = row + rowSpan;
 			var columnEnd = column + columnSpan;
@@ -102,8 +106,9 @@ void UpdateUsedCells(int row, int column, int rowSpan, int columnSpan, bool[][]
 			{
 				for (var c = column; c < columnEnd; c++)
 				{
-					if (usedMatrix[r][c])
+					if (usedMatrix?[r][c] ?? throw new NullReferenceException())
 						LogWarning($"Cell at row {r} column {c} has already been used.");
+
 					usedMatrix[r][c] = true;
 				}
 			}
@@ -114,15 +119,15 @@ void ProcessElement(BindableObject view)
 			var columnSpan = Grid.GetColumnSpan(view);
 			var rowSpan = Grid.GetRowSpan(view);
 
-			FindNextCell(out var row, out var column, out var usedMatrix);
+			FindNextCell(out var row, out var column);
 
 			// Check to see if the user manually assigned a row or column
 			if (view.IsSet(Grid.ColumnProperty))
 				column = Grid.GetColumn(view);
 			if (view.IsSet(Grid.RowProperty))
 				row = Grid.GetRow(view);
 
-			UpdateUsedCells(row, column, rowSpan, columnSpan, usedMatrix);
+			UpdateUsedCells(row, column, rowSpan, columnSpan);
 
 			// Set attributes
 			view.SetValue(Grid.ColumnProperty, column);

src/CommunityToolkit/Xamarin.CommunityToolkit/Behaviors/Validators/NumericValidationBehavior.shared.cs

@@ -78,12 +78,14 @@ public int MaximumDecimalPlaces
 		protected override ValueTask<bool> ValidateAsync(object? value, CancellationToken token)
 		{
 			if (value is not string valueString)
-				throw new ArgumentException($"Expected type string for parameter {nameof(value)}");
+				return new ValueTask<bool>(false);
 
 			if (!(double.TryParse(valueString, out var numeric)
-				&& numeric >= MinimumValue
-				&& numeric <= MaximumValue))
+					&& numeric >= MinimumValue
+					&& numeric <= MaximumValue))
+			{
 				return new ValueTask<bool>(false);
+			}
 
 			var decimalDelimeterIndex = valueString.IndexOf(CultureInfo.CurrentCulture.NumberFormat.NumberDecimalSeparator);
 			var hasDecimalDelimeter = decimalDelimeterIndex >= 0;

src/CommunityToolkit/Xamarin.CommunityToolkit/Converters/VariableMultiValueConverter.shared.cs

@@ -41,7 +41,7 @@ public object Convert(object[]? values, Type targetType, object? parameter, Cult
 			if (boolValues.Length != values.Length)
 				return false;
 
-			var count = boolValues.Count();
+			var count = boolValues.Count(v => v);
 
 			return ConditionType switch
 			{