How to check URL is relative or absolute path

The relative path is a part of following format:


1)  ~/ or / : is the root site


ex: http://serverA/site1/site2/site3/default.aspx, with the current site is Site3, then ~/ will return http://serverA


2) ./: is the current site


3) ../: is the parent site


with above example will return http://serverA/Site1/Site2


The problem is how to check the input url whether using relative path or absolute path.


The simple code can be like this:


public bool IsRelative(string url)
{
    return (url == "~/" || url == "/" || url == "./" || url == "../");
}


But if you want to make sure the functioning work correctly, it should be:

public static bool IsUrlRelative(string url)
{
    Uri uri;
    try
    {
        uri = new Uri(url, UriKind.RelativeOrAbsolute);
    }
    catch
    {
        return false;
    }
    return !uri.IsAbsoluteUri;
}

For now, SharePoint has supported the class to check this, it's very helpful:

SPUrlUtility supported some methods to work on URL:

public static string CombineUrl(string baseUrlPath, string additionalNodes);

return the concatenate 2 string

public static int IndexOfIllegalCharInUrlLeafName(string strLeafName);

return the position of illegal character in your string

public static bool IsLegalCharInUrl(char character);

indicate your character is legal or not

public static bool IsLegalFileName(string name);

indicate your file name is legal or not

public static bool IsProtocolAllowed(string fullOrRelativeUrl);

public static bool IsProtocolAllowed(string fullOrRelativeUrl, bool allowRelativeUrl);

public static bool IsUrlFull(string url);
public static bool IsUrlRelative(string url);