Brush property - Error on getting value for property.

[firstlanetech]

I have an indicator with a Brush property that is used to draw lines on the indicator panel with the specified color (brush).

In the SetDefaults section of OnStateChange, if I set LineColor = Brushes.Red, indicator works fine.

However, if I set using the FromRgb method,

LineColor = new SolidColorBrush(Color.FromRgb(100, 125, 150));

the LineColor property shows the specified color in the settings tab. But when I click Apply / OK, I see the following error -

Error on getting value for property 'LineColor'. The calling thread cannot access this object because a different thread owns it.


I think the issue is with assigning SolidColorBrush to the property during initialization.

How do I fix it ?

        [NinjaScriptProperty]
        [XmlIgnore()]
        [Display(Name = "Line Color", Order = 1, GroupName = "Settings")]
        public Brush LineColor
        {
            get; set;
        }
        [Browsable(false)]
        public string LineColor_Serialize
        {
            get { return Serialize.BrushToString(this.LineColor); }
            set { this.LineColor = Serialize.StringToBrush(value); }
        }​

[firstlanetech]

I read under the documentation of "Creating a Custom Solid Color Brush", that the custom Solid Color Brush must be frozen using the Freeze().

In my case using LineColor.Freeze() immediately solves the problem.

In the OnStateChanged, in the SetDefaults section,

LineColor = new SolidColorBrush(Color.FromRgb(100, 125, 150));
LineColor.Freeze();

Is this the correct approach ? What happens if the user changes the LineColor in settings window ? Is the user specified brush frozen ?

[NinjaTrader_ChelseaB]

Hello firstlanetech,

Yes, this is the correct approach. The brushes are UI objects which exist on the UI thread which requires freezing to use in the NinjaScript thread.

Below are links to the help guide.
Help guide: NinjaScript > Educational Resources > Working with Brushes > Understanding custom brushes
Help guide: NinjaScript > NinjaScript Best Practices > Error handling practices > Using WPF brushes

"What happens if the user changes the LineColor in settings window ? Is the user specified brush frozen ?"

Yes, the user selected color would be used. State.SetDefaults only sets the default value for the variable when the script is first constructed.