Linq.Expression TryCatch - Pass exception to Catch Block?

You need to pass your catched exception to CatchBlock expression as parameter. For this you should do:

• Change signature of HandleException. It will takes a exception as argument:

  public int HandleException(InvalidCastException exp)
  {
      // Put here some real logic. I tested it using line below
      Console.WriteLine(exp.Message);
      return 100;
  }
  

• Use CatchBlock.Variable to pass your handled exception into catch block. You can set it use constructor. Read comment in the code below:

      // Create parameter that will be passed to catch block 
      var excepParam = Expression.Parameter(typeof(InvalidCastException));
  
      MethodInfo handleExceptionMethodInfo = simpleMath.GetType().GetMethods().Where(x => x.Name == "HandleException").ToArray()[0];
      MethodCallExpression returnMethodWithParameters2 = Expression.Call(Expression.Constant(simpleMath), handleExceptionMethodInfo, excepParam);
      UnaryExpression returnMethodWithParametersAsObject2 = Expression.Convert(returnMethodWithParameters2, typeof(object));
  
      // Put created parameter before to CatchBlock.Variable using Expression.Catch 
      // that takes the first argument as ParameterExpression
      TryExpression tryCatchMethod2 = TryExpression.TryCatch(returnMethodWithParametersAsObject, Expression.Catch(excepParam, returnMethodWithParametersAsObject2));
      var exppp = Expression.Lambda<Func<object, object, object>>(tryCatchMethod2, parameters);
      Func<object, object, object> func2 = Expression.Lambda<Func<object, object, object>>(tryCatchMethod2, parameters).Compile();
      object result2 = func2(20, "f"); // result = 100