Question

I have plain text with some custom tags.
For example:

I like C#. <code lang="C#">public static void main</code>
THis is good language.

I need replace all whitespace that’s not inside a tag with  

The text after replace must be:

I&nbsp;like&nbsp;C#.&nbsp;<code lang="C#">public static void main</code>
THis&nbsp;is&nbsp;good&nbsp;language.

Answer 1

If you have valid XML elements mixed with text, you can use XML parsing class, for instance XDocument, you can do it like this:

        string input = @"I like C#. <code lang=""C#"">public static void main</code>THis is good language.";
        string rootedInput = String.Format("<root>{0}</root>", input);

        XDocument doc = XDocument.Parse(rootedInput);
        var nodes = doc.Root.DescendantNodes();

        StringBuilder sb = new StringBuilder();
        string nodeAsString = String.Empty;
        foreach (XNode node in nodes)
        {
            if (node.NodeType == XmlNodeType.Text)
                nodeAsString = node.ToString().Replace(" ", "&nbsp;");
            else
                nodeAsString = node.ToString();

            sb.Append(nodeAsString);
        }

        string newStr = sb.ToString();