Questions

Hi there,

Ok, I seem to remember a couple of examples like this asked before. I did a quick search on google for SciChart MVVM VerticalLineAnnotation and came up with this thread on Vertical Lines with a downloadable sample.

Does this sample help?

I’d suggest taking it one step at a time with MVVM, WPF and C#. There are a mixture of concepts there and quite a steep learning curve. I have been coding WPF applications since 2006, and it took a fair amount of that time to get my head around XAML binding! That being said you’re in the right place, if we can help you, we will.

Best regards,
Andrew

Hi there,

For VerticalLineAnnotation X2 and Y2 are ignored. We have four types of annotation in SciChart which require different coordinates:

• Types which require X1,Y1,X2,Y2 include LineAnnotation, LineArrowAnnotation, BoxAnnotation
• Types which require X1,Y1 only include TextAnnotation, CustomAnnotation
• Types which require just X1 include VerticalLineAnnotation
• Types which require just Y1 include HorizontalLineAnnotation, AxisMarkerAnnotation

So, to get a difference between two VerticalLineAnnotations first you need to use MVVM and databind the VerticalLineAnnotation.X1 property to a property in the viewmodel, e.g.

public double X1First 
{
   get { return x1First; }
   set 
   {  
       x1First = value;
       OnPropertyChanged("X1First");
       OnPropertyChanged("X1Diff");
   } 
}
public double X1Second
{
   get { return x1Second; }
   set 
   {  
       x1Second= value;
       OnPropertyChanged("X1Second");
       OnPropertyChanged("X1Diff");
   } 
}

Next you need to expose a property to output the difference, e.g.

public double X1Diff
{
   get { return Math.Abs(x1First - x1Second); } 
}

Note I raised PropertyChanged for X1Diff whenever the X1First or X1Second are updated by the user dragging the vertical lines.

Finally you must now databind a TextBox to the X1Diff property to output to the user.

This is similar to the principle we use in the Drag Horizontal threshold example, which uses MVVM to bind a horizontal line’s Y1 property to a ViewModel, then depending on this do some changes.

Regarding the remove annotation leaving them active, this is not something we’ve observed ourselves. Can you help us reproduce it?

E.g. if you go to the Create Annotations Dynamically example and add a vertical line, then remove it, this error does not seem to occur.

• Andrew

Thanks for the code to reproduce, that really helps us identifying issues.

Ok so for some reason the Binding to X1 is keeping the annotation alive, not allowing it to be removed. I made a small modification to your code sample like this, nulling the X1 property (removing the binding) before removing the annotation from the collection. This causes the annotation to be completely removed from the canvas.

        private void RemoveVerticalLineAnnotation()
        {
            while (AnnotationCollection.Count != 0)
            {
                var annotation = AnnotationCollection[AnnotationCollection.Count - 1];
                annotation.X1 = null; // Binding keeps annotation alive. Remove it

                AnnotationCollection.Remove(annotation);
            }
            AnnotationCollection.Clear();
 
            n = 0;
        }

Why this occurs I don’t know, we’ll create a bug for investigation, but for now please use the above workaround.

Best regards,
Andrew

Hi there,

It takes default value from Stroke property of the parent annotation(Vertical/HorizontalLineAnnotation) or from axis ticks color if it’s placed on an axis. To change, just set Foreground property on the label.

Hope this helps,

Best regards,
Yuriy

FYI we fixed the bug of bindings keeping annotations alive in v1.7.0.2424, which was released yesterday.

Best regards,
Andrew