To combine file paths with slashes will take care by below code
public static string MergePath(params string[] stringPaths)
        {
            for (int i = 0; i
< stringPaths.Length; i++)
            {
                //To skip
trim on first path
                if (i != 0)
                    stringPaths[i] =
stringPaths[i].Trim().TrimStart(Path.DirectorySeparatorChar).TrimEnd(Path.DirectorySeparatorChar);
            }
            return Path.Combine(stringPaths);
        }
Example:
var stringtest = Extensions.MergePath(@"c:\path\", @"\dir\file.txt");
var stringtest2 = Extensions.MergePath(@"c:\path\",@"\test\adsf\", @"\dir\file.txt");
var stringtest3 = Extensions.MergePath(@"c:\path",
@"test\adsf", @"dir\file.txt");
Output:
"c:\\path\\dir\\file.txt"
"c:\\path\\test\\adsf\\dir\\file.txt"
"c:\\path\\test\\adsf\\dir\\file.txt"