Add GetNamedArgument extension and refactor usage

Introduced a generic GetNamedArgument<T> extension method for AttributeData to simplify retrieval of named arguments. Refactored ReactiveCommandGenerator.Execute.cs to use the new method for accessing the AccessModifier argument.

Author: ChrisPulman

src/ReactiveUI.SourceGenerators.Roslyn/Core/Extensions/AttributeDataExtensions.cs

@@ -3,6 +3,7 @@
 // The ReactiveUI and contributors licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for full license information.
 
+using System;
 using System.Collections.Generic;
 using System.Collections.Immutable;
 using System.Linq;
@@ -44,6 +45,26 @@ public static bool TryGetNamedArgument<T>(this AttributeData attributeData, stri
         return false;
     }
 
+    /// <summary>
+    /// Gets the named argument.
+    /// </summary>
+    /// <typeparam name="T">The type of argument to get.</typeparam>
+    /// <param name="attributeData">The attribute data.</param>
+    /// <param name="name">The name.</param>
+    /// <returns>The named argument value.</returns>
+    public static T? GetNamedArgument<T>(this AttributeData attributeData, string name)
+    {
+        foreach (var properties in attributeData.NamedArguments)
+        {
+            if (properties.Key == name)
+            {
+                return (T?)properties.Value.Value;
+            }
+        }
+
+        return default;
+    }
+
     /// <summary>
     /// Enumerates all items in a flattened sequence of constructor arguments for a given <see cref="AttributeData"/> instance.
     /// </summary>

src/ReactiveUI.SourceGenerators.Roslyn/ReactiveCommand/ReactiveCommandGenerator.Execute.cs

@@ -92,8 +92,7 @@ public partial class ReactiveCommandGenerator
         token.ThrowIfCancellationRequested();
 
         // Get AccessModifier enum value from the attribute
-        attributeData.TryGetNamedArgument("AccessModifier", out int propertyAccessModifier);
-        var accessModifier = propertyAccessModifier switch
+        var accessModifier = attributeData.GetNamedArgument<int>("AccessModifier") switch
         {
             1 => "protected",
             2 => "internal",