Why does != PeriodType.Tick Give me unexpected results?

[Crassius]

I want to show an error message on screen and return if the user applies my indicator to the wrong chart type or size.

The documentation gives this code as an example of BarsPeriod.ID

if (BarsPeriod.Id == PeriodType.Tick && BarsPeriod.Value >=  100)
    {
        //  Indicator calculation logic here
     }

I tried:

if (BarsPeriod.Id != PeriodType.Tick && BarsPeriod.Value !=  100)
    {
        //  Error message code goes here
     }

I don't get what I expect... if I remove

BarsPeriod.Id != PeriodType.Tick

I get the eror message as expected when the chart period is not the one specified, but

... if I leave both conditions in place, the indicator applies itself to the chart, and doesn't display the error message regardless of chart type or period.

Why?

[NinjaTrader_AdamP]

Crassius,

if (BarsPeriod.Id == PeriodType.Tick && BarsPeriod.Value != 100)

This condition checks if the chart is of type "tick" AND the barsperiod value is not equal to 100. Are you trying to negate this statement?

To negate an and statement, you need to use the following De'Morgan's law.

NOT ( Condition1 AND Condition2 ) is the same as ( NOT Condition1 OR NOT Condition2 )

So you would want to use :

(BarsPeriod.Id != PeriodType.Tick || BarsPeriod.Value != 100)

or you can use :

if ( ! (BarsPeriod.Id == PeriodType.Tick && BarsPeriod.Value == 100) )

What sort of charts are you trying to prevent?

[Crassius]

Thanks... I learned something new. Got it.