C# Discriminated Union (開発者のための仕組み)

public abstract class OperationResult<T>
{
    private OperationResult() { }
    public sealed class Success : OperationResult<T>
    {
        public T Value { get; }
        public Success(T value) => Value = value;
        public override string ToString() => $"Success: {Value}";
    }
    public sealed class Failure : OperationResult<T>
    {
        public string Error { get; }
        public Failure(string error) => Error = error;
        public override string ToString() => $"Failure: {Error}";
    }
    public static OperationResult<T> CreateSuccess(T value) => new Success(value);
    public static OperationResult<T> CreateFailure(string error) => new Failure(error);
}

Public MustInherit Class OperationResult(Of T)
	Private Sub New()
	End Sub
	Public NotInheritable Class Success
		Inherits OperationResult(Of T)

		Public ReadOnly Property Value() As T
		Public Sub New(ByVal value As T)
			Me.Value = value
		End Sub
		Public Overrides Function ToString() As String
			Return $"Success: {Value}"
		End Function
	End Class
	Public NotInheritable Class Failure
		Inherits OperationResult(Of T)

		Public ReadOnly Property [Error]() As String
		Public Sub New(ByVal [error] As String)
			Me.Error = [error]
		End Sub
		Public Overrides Function ToString() As String
			Return $"Failure: {[Error]}"
		End Function
	End Class
	Public Shared Function CreateSuccess(ByVal value As T) As OperationResult(Of T)
		Return New Success(value)
	End Function
	Public Shared Function CreateFailure(ByVal [error] As String) As OperationResult(Of T)
		Return New Failure([error])
	End Function
End Class

public string HandleResult(OperationResult<int> result) =>
    result switch
    {
        OperationResult<int>.Success success => $"Operation succeeded with value: {success.Value}",
        OperationResult<int>.Failure failure => $"Operation failed with error: {failure.Error}",
        _ => throw new InvalidOperationException("Unexpected result type")
    };

'INSTANT VB TODO TASK: The following 'switch expression' was not converted by Instant VB:
'public string HandleResult(OperationResult<int> result) => result switch
'	{
'		OperationResult<int>.Success success => $"Operation succeeded with value: {success.Value}",
'		OperationResult<int>.Failure failure => $"Operation failed with error: {failure.Error}",
'		_ => throw new InvalidOperationException("Unexpected result type")
'	};

public static class OperationResultExtensions
{
    public static bool IsSuccess<T>(this OperationResult<T> result) =>
        result is OperationResult<T>.Success;
}

Public Module OperationResultExtensions
	<System.Runtime.CompilerServices.Extension> _
	Public Function IsSuccess(Of T)(ByVal result As OperationResult(Of T)) As Boolean
		Return TypeOf result Is OperationResult(Of T).Success
	End Function
End Module

using IronPdf;
using System;
public abstract class PdfResult
{
    private PdfResult() { }
    public sealed class Success : PdfResult
    {
        public PdfDocument Pdf { get; }
        public Success(PdfDocument pdf) => Pdf = pdf;
        public override string ToString() => "PDF generation succeeded";
    }
    public sealed class Failure : PdfResult
    {
        public string ErrorMessage { get; }
        public Failure(string errorMessage) => ErrorMessage = errorMessage;
        public override string ToString() => $"PDF generation failed: {ErrorMessage}";
    }
    public static PdfResult CreateSuccess(PdfDocument pdf) => new Success(pdf);
    public static PdfResult CreateFailure(string errorMessage) => new Failure(errorMessage);
}
public class PdfGenerator
{
    public PdfResult GeneratePdf(string htmlContent)
    {
        try
        {
            var renderer = new ChromePdfRenderer();
            var pdf = renderer.RenderHtmlAsPdf(htmlContent);
            return PdfResult.CreateSuccess(pdf);
        }
        catch (Exception ex)
        {
            return PdfResult.CreateFailure(ex.Message);
        }
    }
}

Imports IronPdf
Imports System
Public MustInherit Class PdfResult
	Private Sub New()
	End Sub
	Public NotInheritable Class Success
		Inherits PdfResult

		Public ReadOnly Property Pdf() As PdfDocument
		Public Sub New(ByVal pdf As PdfDocument)
			Me.Pdf = pdf
		End Sub
		Public Overrides Function ToString() As String
			Return "PDF generation succeeded"
		End Function
	End Class
	Public NotInheritable Class Failure
		Inherits PdfResult

		Public ReadOnly Property ErrorMessage() As String
		Public Sub New(ByVal errorMessage As String)
			Me.ErrorMessage = errorMessage
		End Sub
		Public Overrides Function ToString() As String
			Return $"PDF generation failed: {ErrorMessage}"
		End Function
	End Class
	Public Shared Function CreateSuccess(ByVal pdf As PdfDocument) As PdfResult
		Return New Success(pdf)
	End Function
	Public Shared Function CreateFailure(ByVal errorMessage As String) As PdfResult
		Return New Failure(errorMessage)
	End Function
End Class
Public Class PdfGenerator
	Public Function GeneratePdf(ByVal htmlContent As String) As PdfResult
		Try
			Dim renderer = New ChromePdfRenderer()
			Dim pdf = renderer.RenderHtmlAsPdf(htmlContent)
			Return PdfResult.CreateSuccess(pdf)
		Catch ex As Exception
			Return PdfResult.CreateFailure(ex.Message)
		End Try
	End Function
End Class