TryCatch.cs

using System;
using System.Threading.Tasks;
using Waher.Events;
using Waher.Script.Abstraction.Elements;
using Waher.Script.Model;
 
namespace Waher.Script.Operators.Conditional
{
    public class TryCatch : BinaryOperator
    {
        public TryCatch(ScriptNode Statement, ScriptNode CatchStatement, int Start, int Length, Expression Expression)
            : base(Statement, CatchStatement, Start, Length, Expression)
        {
        }
 
        public override IElement Evaluate(Variables Variables)
        {
            try
            {
                return this.left.Evaluate(Variables);
            }
            catch (Exception ex)
            {
                object Bak = Variables["Exception"];
                Variables["Exception"] = Log.UnnestException(ex);
                try
                {
                    return this.right.Evaluate(Variables);
                }
                finally
                {
                    if (Bak is null)
                        Variables.Remove("Exception");
                    else
                        Variables["Exception"] = Bak;
                }
            }
        }
 
        public override async Task<IElement> EvaluateAsync(Variables Variables)
        {
            if (!this.isAsync)
                return this.Evaluate(Variables);
 
            try
            {
                return await this.left.EvaluateAsync(Variables);
            }
            catch (Exception ex)
            {
                object Bak = Variables["Exception"];
                Variables["Exception"] = Log.UnnestException(ex);
                try
                {
                    return await this.right.EvaluateAsync(Variables);
                }
                finally
                {
                    if (Bak is null)
                        Variables.Remove("Exception");
                    else
                        Variables["Exception"] = Bak;
                }
            }
        }
    }
}