WPF - Display TextBlock with different colors

Question

so what am trying to do is to display a TextBlock, using a different color for each line, and ideally I would like to use binding.

My TextBlock may display a list of Items, each Item has Texte and Color property. With a foreach, I want to display one line per item, with the Texte property, in specified Color.

I already tried the following :

1)I make a TextBlock, whose Text is binded to a string property in ViewModel, and with a foreach I just fill the string, but in that case cannot apply the colors on each line as I want.

2)I found that link on stack that helped a bit, where it is advised to use the Run.

So in my ViewModel I fill the TextBlock like that :

private TextBlock legende;
public TextBlock Legende
{
   get { return legende; }
   set
   {
     legende = value;
     this.NotifyPropertyChanged("Legende");
   }
}
public void UpdateLegend(Legend legende)
{
    this.Legende = new TextBlock();
    this.Legende.TextWrapping = TextWrapping.Wrap;
    this.Legende.Margin = new Thickness(10);
    this.Legende.FontSize = 14;
    this.Legende.LineStackingStrategy=LineStackingStrategy.BlockLineHeight;
    this.Legende.LineHeight = 20;
    int i = 0;
    foreach(LegendItem item in legende.list)
    {
      if(i==0)
      {
        Run run = new Run(item.Texte);
        run.Foreground = item.Color;
        this.Legende.Inlines.Add(run);
      }
      else
      {
         Run run = new Run(")\r\n"+item.Texte);
         run.Foreground = item.Color;
         this.Legende.Inlines.Add(run);
      }

      i++;
    }
}

My Model does the following, each time I need to update Legend I do :

contexte.UpdateLegend(MonGraphe.Legende);
this.CanvasLegend = contexte.Legende;

Then my View :

<Grid Grid.Column="2" Background="WhiteSmoke">
    <TextBlock x:Name="CanvasLegend" TextAlignment="Left" HorizontalAlignment="Left"/>
</Grid>

For now it is not working at all and I cannot find why. I also would like to do everything in my ViewModel, but for that I would need to bind my Textlock to a TextBlock defined in my ViewModel, but cannot find how to do that?

EDIT :

As explained by Icebat I am using converter as the following :

XML identical to IceBat

ViewModel :

public class ColoringConverter : IValueConverter
    {
        public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
        {
            //is your collection IEnumerable<>? If not, adjust as needed
            var legende = value as Legend;
            if (legende == null) return value;

            return legende.list.Select(i => new Run() { Text = i.Texte, Foreground = i.Color }).ToArray();
        }

        public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
        {
            throw new NotImplementedException();
        }
    }
    class ViewModelMainWindow : INotifyPropertyChanged
    {
        private Legend legende;
        public Legend Legende
        {
            get { return legende; }
            set
            {
                legende = value;
                this.NotifyPropertyChanged("Legende");
            }
        }
}

Also include my "Legende" class, as I think this is where there is missunderstanding :

public class LegendItem 
    {
        public int Type { get; set; }
        public double Diametre { get; set; }
        public double Longueur { get; set; }
        public double Profondeur { get; set; }
        public string Texte { get; set; }
        public Brush Color { get; set; }
        public LegendItem()
        {

        }
    }
    public class Legend : INotifyPropertyChanged
    {
        private ObservableCollection<LegendItem> liste;
        public ObservableCollection<LegendItem> Liste
        {
            get { return liste; }
            set
            {
                liste=value;
                NotifyPropertyChanged(ref liste, value);
            }
        }
        public Legend()
        {
            this.list = new ObservableCollection<LegendItem>();
        }
        public event PropertyChangedEventHandler PropertyChanged;

        public void NotifyPropertyChanged(string propName)
        {
            if (this.PropertyChanged != null)
                this.PropertyChanged(this, new PropertyChangedEventArgs(propName));
        }
        private bool NotifyPropertyChanged<T>(ref T variable, T valeur, [CallerMemberName] string nomPropriete = null)
        {
            if (object.Equals(variable, valeur)) return false;

            variable = valeur;
            NotifyPropertyChanged(nomPropriete);
            return true;
        }
        public Legend(Repere rep)
        {
            List < Brush >  listColors = new List<Brush>();
            listColors.Add(Brushes.Red);
            listColors.Add(Brushes.MediumBlue);
            listColors.Add(Brushes.Purple);
            listColors.Add(Brushes.LimeGreen);
            listColors.Add(Brushes.DarkOrange);
            listColors.Add(Brushes.Navy);
            listColors.Add(Brushes.DarkRed);
            listColors.Add(Brushes.Chartreuse);
            listColors.Add(Brushes.DodgerBlue);
            listColors.Add(Brushes.Tomato);

            this.list = new ObservableCollection<LegendItem>();
            List<Percage> listPer = rep.liste_percages;
            List<GroupePercage> listeGp = rep.listeGpPercages;


            foreach (Percage per in listPer)
            {
                LegendItem itemExists = this.list.FirstOrDefault(x => x.Type == per.Type && x.Diametre == per.Diametre && x.Profondeur == per.Depth&&x.Longueur==per.Longueur);
                if (itemExists == null)
                {
                    LegendItem newItem = new LegendItem();

                    newItem.Type = per.Type;
                    switch (newItem.Type)
                    {
                        case 51: newItem.Texte = "DRILL "; break;
                        case 58: newItem.Texte = "CounterSink "; break;
                        case 59: newItem.Texte = "Tapping "; break;
                        case 12: newItem.Texte = "Slot "; break;
                        default: newItem.Texte = "NOT FOUND "; break;
                    }
                    newItem.Diametre = per.Diametre;
                    newItem.Longueur = per.Longueur;
                    newItem.Texte += newItem.Diametre.ToString();
                    if (newItem.Type==12)
                    {
                        newItem.Texte = newItem.Diametre + " x " + newItem.Longueur;
                    }
                    newItem.Profondeur = per.Depth;
                    this.list.Add(newItem);
                }
            }
            foreach (GroupePercage per in listeGp)
            {
                LegendItem itemExists = this.list.FirstOrDefault(x => x.Type == per.Type && x.Diametre == per.Diametre && x.Profondeur == per.Depth && x.Longueur == per.Longueur);
                if (itemExists == null)
                {
                    LegendItem newItem = new LegendItem();
                    newItem.Type = per.Type;
                    switch (newItem.Type)
                    {
                        case 51: newItem.Texte = "DRILL "; break;
                        case 58: newItem.Texte = "CounterSink "; break;
                        case 59: newItem.Texte = "Tapping "; break;
                        case 12: newItem.Texte = "Slot "; break;
                        default: newItem.Texte = "NOT FOUND "; break;
                    }
                    newItem.Diametre = per.Diametre;
                    newItem.Longueur = per.Longueur;
                    newItem.Texte += newItem.Diametre.ToString();
                    if (newItem.Type == 12)
                    {
                        newItem.Texte = newItem.Diametre + "x" + newItem.Longueur;
                    }
                    newItem.Profondeur = per.Depth;
                    this.list.Add(newItem);
                }
            }
            for(int i=0;i<this.list.Count();i++)
            {
                this.list[i].Color = listColors[Math.Min(i,9)];
            }
        }
    }

Answer 1

Well, the approach with Runs seems to be the simplest one. Not sure where you went wrong, but it all should be relatively easy. You can just use ItemsControl for inlines:

<TextBlock x:Name="CanvasLegend" TextAlignment="Left" HorizontalAlignment="Left">
    <TextBlock.Inlines>
        <ItemsControl ItemsSource="{Binding LegendItems, ElementName=me, 
                                    Converter={StaticResource coloringConverter}}" />
    </TextBlock.Inlines>
</TextBlock>

I use ElementName to point to the host Window here for simplicity, but you can bind it to your ViewModel. The converter looks like this:

public class ColoringConverter : IValueConverter
{
  public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
  {
     //is your collection IEnumerable<>? If not, adjust as needed
     var legend = value as IEnumerable<LegendItem>;
     if (legend == null) return value;

     return legend.Select(i => new Run() { Text = i.Text, Foreground = i.Color }).ToArray();
  }

  public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
  {
     throw new NotImplementedException();
  }
}

Then just add the converter in the resources somewhere (in my example it's Window):

<Window.Resources>
    <local:ColoringConverter x:Key="coloringConverter" />
</Window.Resources>