Changer la couleur et la police d'une partie du texte dans WPF C#

Vous pouvez essayer ce.

public TestWindow()
{
    InitializeComponent();

    this.paragraph = new Paragraph();
    rich1.Document = new FlowDocument(paragraph);

    var from = "user1";
    var text = "chat message goes here";
    paragraph.Inlines.Add(new Bold(new Run(from + ": "))
    {
        Foreground = Brushes.Red
    });
    paragraph.Inlines.Add(text);
    paragraph.Inlines.Add(new LineBreak());
    this.DataContext = this;
}
private Paragraph paragraph;

utilisez donc la propriété Document de la RichTextBox

Vous devez utiliser le Document RichTextBoxExécuter.

propriété du Document: http://msdn.microsoft.com/en-us/library/system.windows.controls.richtextbox.document.aspx

Exécuter: http://msdn.microsoft.com/en-us/library/system.windows.documents.run.aspx

j'ai fait mon propre class pour manipuler Texts de TextBlock,TextBox...

/// <summary>
/// Class for text manipulation operations
/// </summary>
public class TextManipulation
{
    /// <summary>
    /// Is manipulating a specific string inside of a TextPointer Range (TextBlock, TextBox...)
    /// </summary>
    /// <param name="startPointer">Starting point where to look</param>
    /// <param name="endPointer">Endpoint where to look</param>
    /// <param name="keyword">This is the string you want to manipulate</param>
    /// <param name="fontStyle">The new FontStyle</param>
    /// <param name="fontWeight">The new FontWeight</param>
    /// <param name="foreground">The new foreground</param>
    /// <param name="background">The new background</param>
    /// <param name="fontSize">The new FontSize</param>
    public static void FromTextPointer(TextPointer startPointer, TextPointer endPointer, string keyword, FontStyle fontStyle, FontWeight fontWeight, Brush foreground, Brush background, double fontSize)
    {
        FromTextPointer(startPointer, endPointer, keyword, fontStyle, fontWeight, foreground, background, fontSize, null);
    }

    /// <summary>
    /// Is manipulating a specific string inside of a TextPointer Range (TextBlock, TextBox...)
    /// </summary>
    /// <param name="startPointer">Starting point where to look</param>
    /// <param name="endPointer">Endpoint where to look</param>
    /// <param name="keyword">This is the string you want to manipulate</param>
    /// <param name="fontStyle">The new FontStyle</param>
    /// <param name="fontWeight">The new FontWeight</param>
    /// <param name="foreground">The new foreground</param>
    /// <param name="background">The new background</param>
    /// <param name="fontSize">The new FontSize</param>
    /// <param name="newString">The New String (if you want to replace, can be null)</param>
    public static void FromTextPointer(TextPointer startPointer, TextPointer endPointer, string keyword, FontStyle fontStyle, FontWeight fontWeight, Brush foreground, Brush background, double fontSize, string newString)
    {
        if(startPointer == null)throw new ArgumentNullException(nameof(startPointer));
        if(endPointer == null)throw new ArgumentNullException(nameof(endPointer));
        if(string.IsNullOrEmpty(keyword))throw new ArgumentNullException(keyword);

        TextRange text = new TextRange(startPointer, endPointer);
        TextPointer current = text.Start.GetInsertionPosition(LogicalDirection.Forward);
        while (current != null)
        {
            string textInRun = current.GetTextInRun(LogicalDirection.Forward);
            if (!string.IsNullOrWhiteSpace(textInRun))
            {
                int index = textInRun.IndexOf(keyword);
                if (index != -1)
                {
                    TextPointer selectionStart = current.GetPositionAtOffset(index,LogicalDirection.Forward);
                    TextPointer selectionEnd = selectionStart.GetPositionAtOffset(keyword.Length,LogicalDirection.Forward);
                    TextRange selection = new TextRange(selectionStart, selectionEnd);

                    if(!string.IsNullOrEmpty(newString))
                        selection.Text = newString;

                    selection.ApplyPropertyValue(TextElement.FontSizeProperty, fontSize);
                    selection.ApplyPropertyValue(TextElement.FontStyleProperty, fontStyle);
                    selection.ApplyPropertyValue(TextElement.FontWeightProperty, fontWeight);
                    selection.ApplyPropertyValue(TextElement.ForegroundProperty, foreground);
                    selection.ApplyPropertyValue(TextElement.BackgroundProperty, background);
                }
            }
            current = current.GetNextContextPosition(LogicalDirection.Forward);
        }
    }
}

Utilisation

TextManipulation.FromTextPointer(_TextBlock.ContentStart, _TextBlock.ContentEnd, "IWantToBeManipulated", NewFontStyle, NewFontWeight, NewForeground, NewBackground, NewFontSize);
TextManipulation.FromTextPointer(_TextBlock.ContentStart, _TextBlock.ContentEnd, "IWantToBeManipulated", NewFontStyle, NewFontWeight, NewForeground, NewBackground, NewFontSize, "NewStringIfYouWant");