/// <summary>
/// This helper method can be used to convert a relative path to an absolute path based on the given base
/// path.
/// </summary>
/// <param name="basePath">The base path</param>
/// <param name="relativePath">A relative path</param>
/// <returns>An absolute path</returns>
/// <remarks>If the base path is null or empty, the current working folder is used.</remarks>
/// <example>
/// <code lang="cs">
/// string basePath = @"E:\DotNet\CS\TestProject\Source";
/// string relativePath = @"..\Doc\Help.html";
///
/// string absolutePath = FilePath.RelativeToAbsolutePath(basePath,
/// relativePath);
///
/// Console.WriteLine(absolutePath);
///
/// // Results in: E:\DotNet\CS\TestProject\Doc\Help.html
/// </code>
/// <code lang="vbnet">
/// Dim basePath As String = "E:\DotNet\CS\TestProject\Source"
/// Dim relativePath As String = "..\Doc\Help.html"
///
/// Dim absolutePath As String = _
/// FilePath.RelativeToAbsolutePath(basePath, relativePath);
///
/// Console.WriteLine(absolutePath)
///
/// ' Results in: E:\DotNet\CS\TestProject\Doc\Help.html
/// </code>
/// </example>
public static string RelativeToAbsolutePath(string basePath, string relativePath)
{
int idx;
// If blank return the base path
if (String.IsNullOrEmpty(relativePath))
{
return(basePath);
}
// Don't bother if already absolute
if (IOPath.IsPathRooted(relativePath))
{
return(relativePath);
}
// If not specified, use the current folder as the base path
if (basePath == null || basePath.Trim().Length == 0)
{
basePath = Directory.GetCurrentDirectory();
}
else
{
basePath = IOPath.GetFullPath(basePath);
}
// Remove trailing backslashes for comparison
if (FolderPath.IsPathTerminated(basePath))
{
basePath = basePath.Substring(0, basePath.Length - 1);
}
if (relativePath == ".")
{
relativePath = String.Empty;
}
// Remove ".\" or "./" if it's there
if (relativePath.Length > 1 && relativePath[0] == '.' &&
(relativePath[1] == IOPath.DirectorySeparatorChar ||
relativePath[1] == IOPath.AltDirectorySeparatorChar))
{
relativePath = relativePath.Substring(2);
}
// Split the paths into their component parts
string[] baseParts = basePath.Split(IOPath.DirectorySeparatorChar);
string[] relParts = relativePath.Split(IOPath.DirectorySeparatorChar);
// Figure out how far to move up from the relative path
for (idx = 0; idx < relParts.Length; ++idx)
{
if (relParts[idx] != "..")
{
break;
}
}
// If it's below the base path, just add it to the base path
if (idx == 0)
{
return(FilePath.GetFullPath(basePath + IOPath.DirectorySeparatorChar + relativePath));
}
string absPath = String.Join(IOPath.DirectorySeparatorChar.ToString(), baseParts, 0,
Math.Max(0, baseParts.Length - idx));
absPath += IOPath.DirectorySeparatorChar + String.Join(IOPath.DirectorySeparatorChar.ToString(),
relParts, idx, relParts.Length - idx);
return(FilePath.GetFullPath(absPath));
}
/// <summary>
/// This helper method can be used to convert an absolute path to one that is relative to the given base
/// path.
/// </summary>
/// <param name="basePath">The base path</param>
/// <param name="absolutePath">An absolute path</param>
/// <returns>A path to the given absolute path that is relative to the given base path</returns>
/// <remarks>If the base path is null or empty, the current working folder is used.</remarks>
/// <example>
/// <code lang="cs">
/// string basePath = @"E:\DotNet\CS\TestProject\Source";
/// string absolutePath = @"E:\DotNet\CS\TestProject\Doc\Help.html";
///
/// string relativePath = FilePath.AbsoluteToRelativePath(basePath,
/// absolutePath);
///
/// Console.WriteLine(relativePath);
///
/// // Results in: ..\Doc\Help.html
/// </code>
/// <code lang="vbnet">
/// Dim basePath As String = "E:\DotNet\CS\TestProject\Source"
/// Dim absolutePath As String = "E:\DotNet\CS\TestProject\Doc\Help.html"
///
/// Dim relativePath As String = _
/// FilePath.AbsoluteToRelativePath(basePath, absolutePath);
///
/// Console.WriteLine(relativePath)
///
/// ' Results in: ..\Doc\Help.html
/// </code>
/// </example>
public static string AbsoluteToRelativePath(string basePath, string absolutePath)
{
bool hasBackslash = false;
string relPath;
int minLength, idx;
// If not specified, use the current folder as the base path
if (basePath == null || basePath.Trim().Length == 0)
{
basePath = Directory.GetCurrentDirectory();
}
else
{
basePath = IOPath.GetFullPath(basePath);
}
if (absolutePath == null)
{
absolutePath = String.Empty;
}
// Just in case, make sure the path is absolute
if (!IOPath.IsPathRooted(absolutePath))
{
absolutePath = FilePath.GetFullPath(absolutePath);
}
// Remove trailing backslashes for comparison
if (FolderPath.IsPathTerminated(basePath))
{
basePath = basePath.Substring(0, basePath.Length - 1);
}
if (FolderPath.IsPathTerminated(absolutePath))
{
absolutePath = absolutePath.Substring(0, absolutePath.Length - 1);
hasBackslash = true;
}
// Split the paths into their component parts
char[] separators = { IOPath.DirectorySeparatorChar, IOPath.AltDirectorySeparatorChar,
IOPath.VolumeSeparatorChar };
string[] baseParts = basePath.Split(separators);
string[] absParts = absolutePath.Split(separators);
// Find the common base path
minLength = Math.Min(baseParts.Length, absParts.Length);
for (idx = 0; idx < minLength; idx++)
{
if (String.Compare(baseParts[idx], absParts[idx], StringComparison.OrdinalIgnoreCase) != 0)
{
break;
}
}
// Use the absolute path if there's nothing in common (i.e. they are on different drives or network
// shares.
if (idx == 0)
{
relPath = absolutePath;
}
else
{
// If equal to the base path, it doesn't have to go anywhere. Otherwise, work up from the base
// path to the common root.
if (idx == baseParts.Length)
{
relPath = String.Empty;
}
else
{
relPath = new String(' ', baseParts.Length - idx).Replace(" ", ".." +
IOPath.DirectorySeparatorChar);
}
// And finally, add the path from the common root to the absolute path
relPath += String.Join(IOPath.DirectorySeparatorChar.ToString(), absParts, idx,
absParts.Length - idx);
}
return((hasBackslash) ? FolderPath.TerminatePath(relPath) : relPath);
}
