initial commit

Author: Werner Schiller

.gitignore

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+bin/
+obj/
+/packages/
+riderModule.iml
+/_ReSharper.Caches/

ErrorCarrier/Error.cs

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+namespace ErrorCarrier;
+
+public class Error : IError
+{
+    public Exception? InnerException { get; }
+    public string ErrorMessage { get; }
+
+    public bool IsHandled { get; private set; } = false;
+
+    internal Error(string errorMessage)
+    {
+        ErrorMessage = errorMessage;
+    }
+
+    internal Error(Exception innerException)
+    {
+        InnerException = innerException;
+        ErrorMessage = innerException.Message;
+    }
+
+    public TOutput Handle<TOutput>(Func<Error, TOutput> handleErrorAction)
+    {
+        var output = handleErrorAction(this);
+        IsHandled = true;
+        return output;
+    }
+
+    public static implicit operator Exception(Error error)
+    {
+        var unhandledException = error.InnerException;
+        if (unhandledException != null)
+            return unhandledException;
+        return new ErrorMessageException(error.ErrorMessage);
+    }
+}

ErrorCarrier/ErrorCarrier.cs

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+namespace ErrorCarrier;
+
+public class ErrorCarrier<T> : IErrorCarrier
+{
+    public ErrorCarrier(T? valueObject)
+    {
+        ValueObject = valueObject;
+    }
+    
+    public T? ValueObject { get; }
+
+    public static implicit operator T?(ErrorCarrier<T> carrier) => carrier.GetValue();
+
+    private T? GetValue()
+    {
+        if (Errors.All(e => e.IsHandled))
+            return ValueObject;
+        var unHandledErrors = Errors
+            .Where(e => !e.IsHandled)
+            .Cast<Error>()
+            .Select(e => (Exception)e)
+            .ToList();
+        if (unHandledErrors.Count == 1)
+        {
+            throw unHandledErrors.Single();
+        }
+        
+        throw new ExceptionCollectionException(unHandledErrors);
+    }
+
+    public IList<IError> Errors { get; } = new List<IError>();
+}

ErrorCarrier/ErrorCarrier.csproj

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+<Project Sdk="Microsoft.NET.Sdk">
+
+    <PropertyGroup>
+        <TargetFramework>net7.0</TargetFramework>
+        <ImplicitUsings>enable</ImplicitUsings>
+        <Nullable>enable</Nullable>
+    </PropertyGroup>
+
+</Project>

ErrorCarrier/ErrorMessageException.cs

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+namespace ErrorCarrier;
+
+public class ErrorMessageException :  Exception
+{
+    public ErrorMessageException(string unhandledErrorErrorMessage)
+        : base(unhandledErrorErrorMessage)
+    { }
+}

ErrorCarrier/ExceptionCollectionException.cs

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+namespace ErrorCarrier;
+
+public class ExceptionCollectionException : Exception
+{
+    public IList<Exception> InnerExceptions { get; }
+
+    public ExceptionCollectionException(IList<Exception> exceptions)
+        : base($"{exceptions.Count} errors occurred:\n{string.Join(Environment.NewLine, exceptions.ToString())}")
+    {
+        InnerExceptions = exceptions;
+    }
+}

ErrorCarrier/IError.cs

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+namespace ErrorCarrier;
+
+public interface IError
+{
+    string ErrorMessage { get; }
+    Exception? InnerException { get; }
+    bool IsHandled { get; }
+}

ErrorCarrier/IErrorCarrier.cs

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+namespace ErrorCarrier;
+
+public interface IErrorCarrier
+{
+    public IList<IError> Errors { get; }
+}

Helpers.sln

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+
+Microsoft Visual Studio Solution File, Format Version 12.00
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "ErrorCarrier", "ErrorCarrier\ErrorCarrier.csproj", "{DE860415-7459-4E09-AB75-A6008A065934}"
+EndProject
+Global
+	GlobalSection(SolutionConfigurationPlatforms) = preSolution
+		Debug|Any CPU = Debug|Any CPU
+		Release|Any CPU = Release|Any CPU
+	EndGlobalSection
+	GlobalSection(ProjectConfigurationPlatforms) = postSolution
+		{DE860415-7459-4E09-AB75-A6008A065934}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{DE860415-7459-4E09-AB75-A6008A065934}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{DE860415-7459-4E09-AB75-A6008A065934}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{DE860415-7459-4E09-AB75-A6008A065934}.Release|Any CPU.Build.0 = Release|Any CPU
+	EndGlobalSection
+EndGlobal