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GetLongPathName (kernel32)
Converts the specified path to its long form.

C# Signature:

using System.Runtime.InteropServices;
using System.Text;

    [DllImport("kernel32.dll", SetLastError = true, CharSet = CharSet.Auto)]
    [return: MarshalAs(UnmanagedType.U4)]
    private static extern int GetLongPathName(
        string lpszShortPath,
        StringBuilder lpszLongPath,
        int cchBuffer);

User-Defined Types:



The GetLongPathName API call is only available on Windows 98/ME and Windows 2000/XP. It is not available on Windows 95 & NT.

The file must exist to get the correct path. This is because the full path comes from the file system information. If an invalid name is given and exception is not thrown rather the name is just a blank space.

Tips & Tricks:

Please add some!

Sample Code:

    /// <summary>
    /// Converts a short path to a long path.
    /// </summary>
    /// <param name="shortPath">A path that may contain short path elements (~1).</param>
    /// <returns>The long path.  Null or empty if the input is null or empty.</returns>
    internal static string GetLongPathName(string shortPath)
    if (String.IsNullOrEmpty(shortPath))
        return shortPath;

    StringBuilder builder = new StringBuilder(255);
    int result = GetLongPathName(shortPath, builder, builder.Capacity);
    if (result > 0 && result < builder.Capacity)
        return builder.ToString(0, result);
        if (result > 0)
        builder = new StringBuilder(result);
        result = GetLongPathName(shortPath, builder, builder.Capacity);
        return builder.ToString(0, result);
        throw new FileNotFoundException(

Alternative Managed API:

The short name can be used without problem to open files so the only time you would need to use GetLongPathName is if you want to display the path or want to display the file name.

With this alternative you cannot get the long name for the full path but it will resolve the name of the file.

/// <summary>
/// The ToLongName function retrieves the long file name form of a specified short input path
/// </summary>
/// <param name="shortName">The short name path</param>
/// <returns>A long file name string</returns>
public static string ToLongName(string shortName)
    string[] paths = Directory.GetFiles( Path.GetDirectoryName(shortName), Path.GetFileName(shortName) );

    string longName = "";
    if( paths.Length > 0 )
        longName = Path.GetFileNameWithoutExtension( paths[0] );

    return longName;


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