System.Transactions.TransactionManager.ValidateIsolationLevel C# (CSharp) Method

        internal static void ValidateIsolationLevel(IsolationLevel transactionIsolationLevel)
        {
            switch (transactionIsolationLevel)
            {
                case IsolationLevel.Serializable:
                case IsolationLevel.RepeatableRead:
                case IsolationLevel.ReadCommitted:
                case IsolationLevel.ReadUncommitted:
                case IsolationLevel.Unspecified:
                case IsolationLevel.Chaos:
                case IsolationLevel.Snapshot:
                    break;
                default:
                    throw new ArgumentOutOfRangeException(nameof(transactionIsolationLevel));
            }
        }

        public TransactionScope(TransactionScopeOption scopeOption, TransactionOptions transactionOptions, EnterpriseServicesInteropOption interopOption)
        {
            if (!TransactionManager._platformValidated)
            {
                TransactionManager.ValidatePlatform();
            }
            if (DiagnosticTrace.Verbose)
            {
                MethodEnteredTraceRecord.Trace(System.Transactions.SR.GetString("TraceSourceBase"), "TransactionScope.ctor( TransactionScopeOption, TransactionOptions, EnterpriseServicesInteropOption )");
            }
            this.ValidateScopeTimeout("transactionOptions.Timeout", transactionOptions.Timeout);
            TimeSpan timeout = transactionOptions.Timeout;

            transactionOptions.Timeout = TransactionManager.ValidateTimeout(transactionOptions.Timeout);
            TransactionManager.ValidateIsolationLevel(transactionOptions.IsolationLevel);
            this.ValidateInteropOption(interopOption);
            this.interopModeSpecified = true;
            this.interopOption        = interopOption;
            if (this.NeedToCreateTransaction(scopeOption))
            {
                this.committableTransaction = new CommittableTransaction(transactionOptions);
                this.expectedCurrent        = this.committableTransaction.Clone();
            }
            else if (((null != this.expectedCurrent) && (IsolationLevel.Unspecified != transactionOptions.IsolationLevel)) && (this.expectedCurrent.IsolationLevel != transactionOptions.IsolationLevel))
            {
                throw new ArgumentException(System.Transactions.SR.GetString("TransactionScopeIsolationLevelDifferentFromTransaction"), "transactionOptions.IsolationLevel");
            }
            if (((null != this.expectedCurrent) && (null == this.committableTransaction)) && (TimeSpan.Zero != timeout))
            {
                this.scopeTimer = new Timer(new System.Threading.TimerCallback(TransactionScope.TimerCallback), this, timeout, TimeSpan.Zero);
            }
            if (DiagnosticTrace.Information)
            {
                if (null == this.expectedCurrent)
                {
                    TransactionScopeCreatedTraceRecord.Trace(System.Transactions.SR.GetString("TraceSourceBase"), TransactionTraceIdentifier.Empty, TransactionScopeResult.NoTransaction);
                }
                else
                {
                    TransactionScopeResult usingExistingCurrent;
                    if (null == this.committableTransaction)
                    {
                        usingExistingCurrent = TransactionScopeResult.UsingExistingCurrent;
                    }
                    else
                    {
                        usingExistingCurrent = TransactionScopeResult.CreatedTransaction;
                    }
                    TransactionScopeCreatedTraceRecord.Trace(System.Transactions.SR.GetString("TraceSourceBase"), this.expectedCurrent.TransactionTraceId, usingExistingCurrent);
                }
            }
            this.PushScope();
            if (DiagnosticTrace.Verbose)
            {
                MethodExitedTraceRecord.Trace(System.Transactions.SR.GetString("TraceSourceBase"), "TransactionScope.ctor( TransactionScopeOption, TransactionOptions, EnterpriseServicesInteropOption )");
            }
        }