Dear team,
private void diagram1_LinkCreated(object sender, LinkEventArgs e)
  {
if(logic)
            {
                // e.Link.Style.Brush = new MindFusion.Drawing.SolidBrush(Color.Green);
                e.Link.Style.StrokeThickness = 3;
                e.Link.Pen = new MindFusion.Drawing.Pen(Color.Green);
         
            }

    
}
NullReferenceException in StrokeThickness

in form load i have set as

Theme theme = new Theme();
            DiagramLinkStyle style = new DiagramLinkStyle();
            style.Brush = new MindFusion.Drawing.SolidBrush(Color.FromArgb(192, 192, 192));
            style.Stroke = new MindFusion.Drawing.SolidBrush(Color.FromArgb(80, 80, 80));
            style.StrokeThickness = 3;
            theme.RegisterStyle(typeof(DiagramLink), style);
            diagram1.Theme = theme;

Hi,

DiagramLink.Style is null by default, which makes the link use appearance values from current theme. You will need to assign a new Style instance to the link before setting its attributes.

Regards,
Slavcho
Mindfusion