#region preprocessor directives not converted

[ViacheslavUKR]

Sorry, my friend, this is very interesting project to me, because I write in rare lang VB.NET, but any call your converter induce error below. This is input C# code for call this issue ( from wordwide C# example "contoso university").

#define Final // or Intro

#if Intro
#region snippet_Intro
using System.Collections.Generic;
using System.ComponentModel.DataAnnotations.Schema;

namespace ContosoUniversity.Models
{
    public class Course
    {
        [DatabaseGenerated(DatabaseGeneratedOption.None)]
        public int CourseID { get; set; }
        public string Title { get; set; }
        public int Credits { get; set; }

        public ICollection<Enrollment> Enrollments { get; set; }
    }
}
#endregion

#elif Final
#region snippet_Final
using System.Collections.Generic;
using System.ComponentModel.DataAnnotations;
using System.ComponentModel.DataAnnotations.Schema;

namespace ContosoUniversity.Models
{
    public class Course
    {
        [DatabaseGenerated(DatabaseGeneratedOption.None)]
        [Display(Name = "Number")]
        public int CourseID { get; set; }

        [StringLength(50, MinimumLength = 3)]
        public string Title { get; set; }

        [Range(0, 5)]
        public int Credits { get; set; }

        public int DepartmentID { get; set; }

        public Department Department { get; set; }
        public ICollection<Enrollment> Enrollments { get; set; }
        public ICollection<CourseAssignment> CourseAssignments { get; set; }
    }
}
#endregion
#endif


---------------------------
Microsoft Visual Studio
---------------------------
Convert C# to VB:

Selected C# code seems to have errors or to be incomplete:



----- Exception 1 of 1 -----

System.InvalidOperationException: Nullable object must have a value.
   at System.ThrowHelper.ThrowInvalidOperationException(ExceptionResource resource)
   at ICSharpCode.CodeConverter.VB.CSharpConverter.NodesVisitor.ConvertAndSplitAttributes(SyntaxList`1 attributeLists, SyntaxList`1& attributes, SyntaxList`1& returnAttributes)
   at ICSharpCode.CodeConverter.VB.CSharpConverter.NodesVisitor.VisitPropertyDeclaration(PropertyDeclarationSyntax node)
   at Microsoft.CodeAnalysis.CSharp.Syntax.PropertyDeclarationSyntax.Accept[TResult](CSharpSyntaxVisitor`1 visitor)
   at ICSharpCode.CodeConverter.VB.CSharpConverter.NodesVisitor.<VisitClassDeclaration>b__22_0(MemberDeclarationSyntax m)
   at System.Linq.Enumerable.WhereSelectEnumerableIterator`2.MoveNext()
   at System.Collections.Generic.List`1..ctor(IEnumerable`1 collection)
   at System.Linq.Enumerable.ToList[TSource](IEnumerable`1 source)
   at ICSharpCode.CodeConverter.VB.CSharpConverter.NodesVisitor.VisitClassDeclaration(ClassDeclarationSyntax node)
   at Microsoft.CodeAnalysis.CSharp.Syntax.ClassDeclarationSyntax.Accept[TResult](CSharpSyntaxVisitor`1 visitor)
   at ICSharpCode.CodeConverter.VB.CSharpConverter.NodesVisitor.<VisitNamespaceDeclaration>b__20_0(MemberDeclarationSyntax m)
   at System.Linq.Enumerable.WhereSelectEnumerableIterator`2.MoveNext()
   at Microsoft.CodeAnalysis.SyntaxList`1.CreateNode(IEnumerable`1 nodes)
   at ICSharpCode.CodeConverter.VB.CSharpConverter.NodesVisitor.VisitNamespaceDeclaration(NamespaceDeclarationSyntax node)
   at Microsoft.CodeAnalysis.CSharp.Syntax.NamespaceDeclarationSyntax.Accept[TResult](CSharpSyntaxVisitor`1 visitor)
   at ICSharpCode.CodeConverter.VB.CSharpConverter.NodesVisitor.<VisitCompilationUnit>b__14_1(MemberDeclarationSyntax m)
   at System.Linq.Enumerable.WhereSelectEnumerableIterator`2.MoveNext()
   at Microsoft.CodeAnalysis.SyntaxList`1.CreateNode(IEnumerable`1 nodes)
   at ICSharpCode.CodeConverter.VB.CSharpConverter.NodesVisitor.VisitCompilationUnit(CompilationUnitSyntax node)
   at Microsoft.CodeAnalysis.CSharp.Syntax.CompilationUnitSyntax.Accept[TResult](CSharpSyntaxVisitor`1 visitor)
   at ICSharpCode.CodeConverter.VB.CSharpConverter.Convert(CSharpSyntaxNode input, SemanticModel semanticModel, Document targetDocument)
   at ICSharpCode.CodeConverter.VB.CSharpConverter.ConvertText(String text, MetadataReference[] references)


---------------------------
OK   
---------------------------

Also I start your project in source code and see a code line number with error. Please see below.

Error message:
----- Exception 1 of 1 -----

System.InvalidOperationException: Nullable object must have a value.
   at System.ThrowHelper.ThrowInvalidOperationException(ExceptionResource resource)
   at System.Nullable`1.get_Value()
   at ICSharpCode.CodeConverter.VB.CSharpConverter.NodesVisitor.ConvertAndSplitAttributes(SyntaxList`1 attributeLists, SyntaxList`1& attributes, SyntaxList`1& returnAttributes) in F:\Projects\CodeConverter-master\ICSharpCode.CodeConverter\VB\NodesVisitor.cs:line 523
   at ICSharpCode.CodeConverter.VB.CSharpConverter.NodesVisitor.VisitPropertyDeclaration(PropertyDeclarationSyntax node) in F:\Projects\CodeConverter-master\ICSharpCode.CodeConverter\VB\NodesVisitor.cs:line 431
   at Microsoft.CodeAnalysis.CSharp.Syntax.PropertyDeclarationSyntax.Accept[TResult](CSharpSyntaxVisitor`1 visitor)
   at ICSharpCode.CodeConverter.VB.CSharpConverter.NodesVisitor.<VisitClassDeclaration>b__22_0(MemberDeclarationSyntax m) in F:\Projects\CodeConverter-master\ICSharpCode.CodeConverter\VB\NodesVisitor.cs:line 206
   at System.Linq.Enumerable.WhereSelectEnumerableIterator`2.MoveNext()
   at System.Collections.Generic.List`1..ctor(IEnumerable`1 collection)
   at System.Linq.Enumerable.ToList[TSource](IEnumerable`1 source)
   at ICSharpCode.CodeConverter.VB.CSharpConverter.NodesVisitor.VisitClassDeclaration(ClassDeclarationSyntax node) in F:\Projects\CodeConverter-master\ICSharpCode.CodeConverter\VB\NodesVisitor.cs:line 206
   at Microsoft.CodeAnalysis.CSharp.Syntax.ClassDeclarationSyntax.Accept[TResult](CSharpSyntaxVisitor`1 visitor)
   at ICSharpCode.CodeConverter.VB.CSharpConverter.NodesVisitor.<VisitNamespaceDeclaration>b__20_0(MemberDeclarationSyntax m) in F:\Projects\CodeConverter-master\ICSharpCode.CodeConverter\VB\NodesVisitor.cs:line 180
   at System.Linq.Enumerable.WhereSelectEnumerableIterator`2.MoveNext()
   at Microsoft.CodeAnalysis.SyntaxList`1.CreateNode(IEnumerable`1 nodes)
   at Microsoft.CodeAnalysis.SyntaxList`1..ctor(IEnumerable`1 nodes)
   at Microsoft.CodeAnalysis.VisualBasic.SyntaxFactory.List[TNode](IEnumerable`1 nodes)
   at ICSharpCode.CodeConverter.VB.CSharpConverter.NodesVisitor.VisitNamespaceDeclaration(NamespaceDeclarationSyntax node) in F:\Projects\CodeConverter-master\ICSharpCode.CodeConverter\VB\NodesVisitor.cs:line 182
   at Microsoft.CodeAnalysis.CSharp.Syntax.NamespaceDeclarationSyntax.Accept[TResult](CSharpSyntaxVisitor`1 visitor)
   at ICSharpCode.CodeConverter.VB.CSharpConverter.NodesVisitor.<VisitCompilationUnit>b__14_1(MemberDeclarationSyntax m) in F:\Projects\CodeConverter-master\ICSharpCode.CodeConverter\VB\NodesVisitor.cs:line 118
   at System.Linq.Enumerable.WhereSelectEnumerableIterator`2.MoveNext()
   at Microsoft.CodeAnalysis.SyntaxList`1.CreateNode(IEnumerable`1 nodes)
   at Microsoft.CodeAnalysis.SyntaxList`1..ctor(IEnumerable`1 nodes)
   at Microsoft.CodeAnalysis.VisualBasic.SyntaxFactory.List[TNode](IEnumerable`1 nodes)
   at ICSharpCode.CodeConverter.VB.CSharpConverter.NodesVisitor.VisitCompilationUnit(CompilationUnitSyntax node) in F:\Projects\CodeConverter-master\ICSharpCode.CodeConverter\VB\NodesVisitor.cs:line 118
   at Microsoft.CodeAnalysis.CSharp.Syntax.CompilationUnitSyntax.Accept[TResult](CSharpSyntaxVisitor`1 visitor)
   at ICSharpCode.CodeConverter.VB.CSharpConverter.Convert(CSharpSyntaxNode input, SemanticModel semanticModel, Document targetDocument) in F:\Projects\CodeConverter-master\ICSharpCode.CodeConverter\VB\CSharpConverter.cs:line 33
   at ICSharpCode.CodeConverter.VB.CSharpConverter.ConvertText(String text, MetadataReference[] references) in F:\Projects\CodeConverter-master\ICSharpCode.CodeConverter\VB\CSharpConverter.cs:line 46

[ViacheslavUKR]

I add one string of code

if (attrList.Target != null) {
	if (SyntaxTokenExtensions.IsKind((SyntaxToken)attrList.Target?.Identifier, CS.SyntaxKind.ReturnKeyword) == true)
		retAttr.Add((AttributeListSyntax)attrList.Accept(this));
	else
		attr.Add((AttributeListSyntax)attrList.Accept(this));
}

But all this project has built in crazy and insecure style. I'm don't understand this style of programming

If (Obj1.Obj2.Ob3.Obj4.Property = bla-bla-bla) than ... bla-bla-bla

are you have understanding that in any moment Obj1 may equal null, or Obj2 in any moment may equal null ... hmmm .... VB-programmer usually use only one variable in one operator, and in top of each sub or function before doing sensitive function need to check all parameters to correct value. And if possible need don't use expression future. This is my style, and I usually working as freelancer and I see thousands of VB-project. I think this is main stream of style of VB-programmer - firstly check any variable on top of function and after that use less as possible variables in one code string. Sorry, my friend, for this description, but I really don't understand your style of programming.

and second problem in shallow view - its support not all C# and VB syntax - for example directive #define this project fully ignore.

Very sorry.

[GrahamTheCoder]

Thank you for including example code and error message, that's very helpful!

You are correct that some language features like this are still unsupported. Over time (and with the help of the community) we hope to cover much more.

If you intend to work on implementing #define#, be aware of this issue where me and someone else are currently changing how Trivia is handled, so will touch similar areas: #8 (comment)

The code style makes frequent use of the reasonably new operator ?. which you may want to read about if you aren't familiar https://docs.microsoft.com/en-us/dotnet/csharp/language-reference/operators/null-conditional-operators
This allows a more concise version of the pattern you've described.

[GrahamTheCoder]

As of 5.6.1, the attribute issue is fixed. Preprocessor directives are still not supported so I'll leave this issue open to track that. It may be extremely difficult to correctly convert preprocessor directives in cases such as this: #8 (comment)
However, support for #if statments that only contain whole nodes should be reasonably easy and cater for a lot of real-world cases.

[GrahamTheCoder]

#if statments that only contain whole nodes should be reasonably easy and cater for a lot of real-world cases.

After looking more closely at what's available in Roslyn, even this looks to be a challenge.
Exactly because of the complex cases where individual tokens are added/removed, the preprocessor directives are resolved at parse time. This means that multiple passes will be needed in order to capture all the possible parsings - 1 pass for each combination of values of constants used in preprocessor directives. This could obviously get expensive very quickly...
All these passes will also need to be pieced together back into a single document afterwards which could take some significant restructuring of code.

If Roslyn will deal with a bit of ambiguity it might yield acceptable results for simple cases, to just discover all constants, and set them all to true, which I'll try out some time, but anything more is definitely going to be punted way down the line.

There are some other preprocessor directives such as enabling/disabling warnings that should be much easier to convert.