Added various extensions.

Added coding style helpers.
Unit tests.

SystemExtensions.NetStandard/Extensions/Result.cs

@@ -0,0 +1,185 @@
+namespace System.Extensions
+{
+    public class Result<TSuccess, TFailure>
+    {
+        private readonly object value;
+
+        public Result(TSuccess successValue)
+        {
+            value = successValue;
+        }
+        public Result(TFailure failureValue)
+        {
+            value = failureValue;
+        }
+
+        public bool TryExtractSuccess(out TSuccess successValue)
+        {
+
+            if (value is TSuccess success)
+            {
+                successValue = success;
+                return true;
+            }
+            else
+            {
+                successValue = default;
+                return false;
+            }
+        }
+        public bool TryExtractFailure(out TFailure failureValue)
+        {
+
+            if (value is TFailure failure)
+            {
+                failureValue = failure;
+                return true;
+            }
+            else
+            {
+                failureValue = default;
+                return false;
+            }
+        }
+        public Result<TSuccess, TFailure> Do(Action onSuccess, Action onFailure)
+        {
+            if (onSuccess is null) throw new ArgumentNullException(nameof(onSuccess));
+
+            if (onFailure is null) throw new ArgumentNullException(nameof(onFailure));
+
+            if (value is TSuccess)
+            {
+                onSuccess.Invoke();
+            }
+            else if (value is TFailure)
+            {
+                onFailure.Invoke();
+            }
+            return this;
+        }
+        public Result<TSuccess, TFailure> DoAny(Action onSuccess = null, Action onFailure = null)
+        {
+            if (value is TSuccess)
+            {
+                onSuccess?.Invoke();
+            }
+            else if (value is TFailure)
+            {
+                onFailure?.Invoke();
+            }
+            return this;
+        }
+        public Result<TSuccess, TFailure> Do(Action<TSuccess> onSuccess, Action<TFailure> onFailure)
+        {
+            if (onSuccess is null) throw new ArgumentNullException(nameof(onSuccess));
+
+            if (onFailure is null) throw new ArgumentNullException(nameof(onFailure));
+
+            if (value is TSuccess success)
+            {
+                onSuccess.Invoke(success);
+            }
+            else if (value is TFailure failure)
+            {
+                onFailure.Invoke(failure);
+            }
+            return this;
+        }
+        public Result<TSuccess, TFailure> DoAny(Action<TSuccess> onSuccess = null, Action<TFailure> onFailure = null)
+        {
+            if (value is TSuccess success)
+            {
+                onSuccess?.Invoke(success);
+            }
+            else if (value is TFailure failure)
+            {
+                onFailure?.Invoke(failure);
+            }
+            return this;
+        }
+        public T Switch<T>(Func<TSuccess, T> onSuccess, Func<TFailure, T> onFailure)
+        {
+            if (onSuccess is null) throw new ArgumentNullException(nameof(onSuccess));
+
+            if (onFailure is null) throw new ArgumentNullException(nameof(onFailure));
+
+            if (value is TSuccess success)
+            {
+                return onSuccess.Invoke(success);
+            }
+            else if (value is TFailure failure)
+            {
+                return onFailure.Invoke(failure);
+            }
+            throw new InvalidOperationException($"{nameof(value)} must be of type {typeof(TSuccess)} or {typeof(TFailure)} in order to switch to {typeof(T)}");
+        }
+        public T SwitchAny<T>(Func<TSuccess, T> onSuccess = null, Func<TFailure, T> onFailure = null)
+        {
+            if (value is TSuccess success)
+            {
+                return onSuccess is null ? default : onSuccess.Invoke(success);
+            }
+            else if (value is TFailure failure)
+            {
+                return onFailure is null ? default : onFailure.Invoke(failure);
+            }
+            throw new InvalidOperationException($"{nameof(value)} must be of type {typeof(TSuccess)} or {typeof(TFailure)} in order to switch to {typeof(T)}");
+        }
+        public Result<V, K> Switch<V, K>(Func<TSuccess, V> onSuccess, Func<TFailure, K> onFailure)
+        {
+            if (onSuccess is null) throw new ArgumentNullException(nameof(onSuccess));
+
+            if (onFailure is null) throw new ArgumentNullException(nameof(onFailure));
+
+            if (value is TSuccess success)
+            {
+                return Result<V, K>.Success(onSuccess.Invoke(success));
+            }
+            else if (value is TFailure failure)
+            {
+                return Result<V, K>.Failure(onFailure.Invoke(failure));
+            }
+            throw new InvalidOperationException($"{nameof(value)} must be of type {typeof(TSuccess)} or {typeof(TFailure)} in order to switch to Result of type {typeof(V)} or {typeof(K)}");
+        }
+        public Result<V, K> SwitchAny<V, K>(Func<TSuccess, V> onSuccess, Func<TFailure, K> onFailure)
+        {
+            if (value is TSuccess success)
+            {
+                return Result<V, K>.Success(onSuccess is null ? default : onSuccess.Invoke(success));
+            }
+            else if (value is TFailure failure)
+            {
+                return Result<V, K>.Failure(onFailure is null ? default : onFailure.Invoke(failure));
+            }
+            throw new InvalidOperationException($"{nameof(value)} must be of type {typeof(TSuccess)} or {typeof(TFailure)} in order to switch to Result of type {typeof(V)} or {typeof(K)}");
+        }
+        public Optional<TSuccess> ToOptional()
+        {
+            if (value is TSuccess)
+            {
+                return Optional.FromValue(value.Cast<TSuccess>());
+            }
+
+            return Optional.None<TSuccess>();
+        }
+
+        public static implicit operator Result<TSuccess, TFailure>(TSuccess success)
+        {
+            return Success(success);
+        }
+
+        public static implicit operator Result<TSuccess, TFailure>(TFailure failure)
+        {
+            return Failure(failure);
+        }
+
+        public static Result<TSuccess, TFailure> Success(TSuccess value)
+        {
+            return new Result<TSuccess, TFailure>(value);
+        }
+        public static Result<TSuccess, TFailure> Failure(TFailure value)
+        {
+            return new Result<TSuccess, TFailure>(value);
+        }
+    }
+}