How to get char/text after my set keyword in richtextbox WPF C#

Question

I want to get char/word after my keyword. In my code I've got keyword = function. When user writes in richtextbox "function a" I need to get "a" and I can't set in like function because this will be inserted by a user. My code look like this:

string keyword = "function";
string newString = randomString;
TextRange text = new TextRange(_richTextBox.Document.ContentStart, _richTextBox.Document.ContentEnd);
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);
                    selection.Text = newString;
                    selection.ApplyPropertyValue(TextElement.FontWeightProperty, FontWeights.Bold);
                    _richTextBox.Selection.Select(selection.Start, selection.End);
                    _richTextBox.Focus();
                }
            }
            current = current.GetNextContextPosition(LogicalDirection.Forward);

Answer 1

This is a job for Regular Expressions . I highly advise you learn how to use them, as they are incredibly powerful. Here is an example of what you could do:

public void ExecuteCommand (string commandText)
{
    var match = Regex.Match(commandText, @"^(\w+)\s*(.*)$");
    if (match.Success)
    {
        string keyword = match.Groups[1].Value;
        string parameters = match.Groups[2].Value;

        switch (keyword)
        {
            case "function":
                MyFunction(parameters);
                break;
            default:
                throw new NotImplementedException();
        }
    }
}