替换文本框中的特定文本 C#

Question

I'm trying to implement a solution to remove a URL from a textbox and replace it with ""

So something like this:

"Hey check out this site http://www.anywhere.com"

Would become:

"Hey check out this site <URL Quarantined>"

This is what I've got at the moment but I don't think I'm doing this correctly, any help would be really appreciated: :)

private void btnFilter_Click(object sender, RoutedEventArgs e)
{
    if (txtContent.Text.Contains("http:"))
    {
        txtContent.Text.Replace("http", "<URL Quarrantined>");
    }
}

Answer 1

Your example is only replacing "http", of course. If you want to replace the whole URL you will have to resort to regular expressions like this:

Regex regex = new Regex(@"http(s)?://([\w-]+.)+[\w-]+(/[\w- ./?%&=])?");
txtContent.Text = regex.Replace(txtContent.Text, "<URL Quarrantined>");

Answer 2

Find the index of "http" and create a new string:

static string Convert(string s)
{
    const string t = "<URL Quarantined>";
    int index = s.LastIndexOf("http");
    if (index != -1)
        return string.Concat(s.AsSpan().Slice(0, s.Length - index + 1), t);

    return s;
}

Usage:

string s = Convert("Hey check out this site http://www.anywhere.com");

Or:

txtContent.Text = Convert(txtContent.Text);

The .NET Framework Substring version allocates an additional string:

static string Convert(string s)
{
    const string t = "<URL Quarantined>";
    int index = s.LastIndexOf("http");
    if (index != -1)
        return string.Concat(s.Substring(0, s.Length - index + 1), t);

    return s;
}