Keep optional parameters for parameterized properties - fixes #642

Author: GrahamTheCoder

CHANGELOG.md

@@ -11,6 +11,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/)
 ### VB -> C#
 * All handlers from multi-line handles syntax now converted [#701](https://github.com/icsharpcode/CodeConverter/issues/701)
 * Implicilty typed inherited events no longer create extra delegates [#700](https://github.com/icsharpcode/CodeConverter/issues/700)
+* Keep optional parameters for parameterized properties [#642](https://github.com/icsharpcode/CodeConverter/issues/642)
 
 ### C# -> VB
 

CodeConverter/CSharp/DeclarationNodeVisitor.cs

@@ -726,8 +726,7 @@ await a.AcceptAsync<AccessorDeclarationSyntax>(TriviaConvertingDeclarationVisito
                 }
                 if (propSymbol.SetMethod != null) {
                     var setMethod = await CreateMethodDeclarationSyntaxAsync(node.ParameterList, SetMethodId(node), true);
-                    var valueParam = SyntaxFactory.Parameter(CommonConversions.CsEscapedIdentifier("value")).WithType(rawType);
-                    setMethod = setMethod.AddParameterListParameters(valueParam);
+                    setMethod = AddValueSetParameter(propSymbol, setMethod, rawType);
                     methodDeclarationSyntaxs.Add(setMethod);
                 }
                 _additionalDeclarations.Add(node, methodDeclarationSyntaxs.Skip(1).ToArray());
@@ -905,7 +904,7 @@ await asClause.Type.AcceptAsync<TypeSyntax>(_triviaConvertingExpressionVisitor,
 
                     if (await ShouldConvertAsParameterizedPropertyAsync(containingPropertyStmt)) {
                         var setMethod = await CreateMethodDeclarationSyntax(containingPropertyStmt?.ParameterList, true);
-                        return setMethod.AddParameterListParameters(SyntaxFactory.Parameter(CommonConversions.CsEscapedIdentifier("value")).WithType(returnType));
+                        return AddValueSetParameter(declaredPropSymbol, setMethod, returnType);
                     }
                     break;
                 case VBasic.SyntaxKind.AddHandlerAccessorBlock:
@@ -939,6 +938,13 @@ async Task<MethodDeclarationSyntax> CreateMethodDeclarationSyntax(VBSyntax.Param
             }
         }
 
+        private static MethodDeclarationSyntax AddValueSetParameter(IPropertySymbol declaredPropSymbol, MethodDeclarationSyntax setMethod, TypeSyntax returnType)
+        {
+            var valueParam = SyntaxFactory.Parameter(CommonConversions.CsEscapedIdentifier("value")).WithType(returnType);
+            if (declaredPropSymbol?.Parameters.Any(p => p.IsOptional) == true) valueParam = valueParam.WithDefault(SyntaxFactory.EqualsValueClause(ValidSyntaxFactory.DefaultExpression));
+            return setMethod.AddParameterListParameters(valueParam);
+        }
+
         private static string SetMethodId(VBSyntax.PropertyStatementSyntax containingPropertyStmt)
         {
             return $"set_{(containingPropertyStmt.Identifier.Text)}";

CodeConverter/CSharp/ExpressionNodeVisitor.cs

@@ -1069,8 +1069,8 @@ public override async Task<CSharpSyntaxNode> VisitParameter(VBSyntax.ParameterSy
             }
 
             EqualsValueClauseSyntax @default = null;
-            // Parameterized properties get compiled/converted to a methd with non-optional parameters
-            if (node.Default != null && node.Parent?.Parent?.IsKind(VBasic.SyntaxKind.PropertyStatement) != true) {
+            // Parameterized properties get compiled/converted to a method with non-optional parameters
+            if (node.Default != null) {
                 var defaultValue = node.Default.Value.SkipIntoParens();
                 if (_semanticModel.GetTypeInfo(defaultValue).Type?.SpecialType == SpecialType.System_DateTime) {
                     var constant = _semanticModel.GetConstantValue(defaultValue);

Tests/CSharp/MemberTests/PropertyMemberTests.cs

@@ -165,7 +165,7 @@ public void Foo()
 }", hasLineCommentConversionIssue: true);//TODO: Improve comment mapping for parameterized property
         }
 
-        [Fact]
+        [Fact] //https://github.com/icsharpcode/CodeConverter/issues/642
         public async Task TestOptionalParameterizedPropertyAsync()
         {
             await TestConversionVisualBasicToCSharpAsync(
@@ -195,12 +195,12 @@ internal partial class TestClass
     public string FirstName { get; set; }
     public string LastName { get; set; }
 
-    public string get_FullName(bool isFirst)
+    public string get_FullName(bool isFirst = false)
     {
         return FirstName + "" "" + LastName;
     }
 
-    internal void set_FullName(bool isFirst, string value)
+    internal void set_FullName(bool isFirst = false, string value = default)
     {
         if (isFirst)
             FirstName = value;