using System;

using System.Text.Json;

using System.Text.RegularExpressions;                   

​

public class Program

{

    public static void Main()

    {

        var line = @"C:\test";

        string escapedSetting = JsonEncodedText.Encode(line, System.Text.Encodings.Web.JavaScriptEncoder.UnsafeRelaxedJsonEscaping).ToString();

        Console.WriteLine(escapedSetting);

    }

}