Access a Remote Directory from C#
Asked Answered
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3

18

I am trying to access a remote network share from a C# program in asp.net. What I need is something like

function download(dirname)
{
    directory = (This is the part I don't know how to do)

    for dir in directory:
        download(dir);

    for file in directory:
        copyfile(file);

}

My problem is that the directory requires a username and password for access and I don't know how to provide them. Thanks for any help you can offer.

Polynices answered 25/3, 2011 at 14:9 Comment(2)
Possible duplicate of this question?Suppuration
Try this answerFranni
S
34

Use this class to authenticate and than just use simple file operations:

/// <summary>
/// Represents a network connection along with authentication to a network share.
/// </summary>
public class NetworkConnection : IDisposable
{
    #region Variables

    /// <summary>
    /// The full path of the directory.
    /// </summary>
    private readonly string _networkName;

    #endregion

    #region Constructors

    /// <summary>
    /// Initializes a new instance of the <see cref="NetworkConnection"/> class.
    /// </summary>
    /// <param name="networkName">
    /// The full path of the network share.
    /// </param>
    /// <param name="credentials">
    /// The credentials to use when connecting to the network share.
    /// </param>
    public NetworkConnection(string networkName, NetworkCredential credentials)
    {
        _networkName = networkName;

        var netResource = new NetResource
                          {
                              Scope = ResourceScope.GlobalNetwork, 
                              ResourceType = ResourceType.Disk, 
                              DisplayType = ResourceDisplaytype.Share, 
                              RemoteName = networkName.TrimEnd('\\')
                          };

        var result = WNetAddConnection2(
            netResource, credentials.Password, credentials.UserName, 0);

        if (result != 0)
        {
            throw new Win32Exception(result);
        }
    }

    #endregion

    #region Events

    /// <summary>
    /// Occurs when this instance has been disposed.
    /// </summary>
    public event EventHandler<EventArgs> Disposed;

    #endregion

    #region Public methods

    /// <summary>
    /// Performs application-defined tasks associated with freeing, releasing, or resetting unmanaged resources.
    /// </summary>
    public void Dispose()
    {
        Dispose(true);
        GC.SuppressFinalize(this);
    }

    #endregion

    #region Protected methods

    /// <summary>
    /// Performs application-defined tasks associated with freeing, releasing, or resetting unmanaged resources.
    /// </summary>
    /// <param name="disposing"><c>true</c> to release both managed and unmanaged resources; <c>false</c> to release only unmanaged resources.</param>
    protected virtual void Dispose(bool disposing)
    {
        if (disposing)
        {
            var handler = Disposed;
            if (handler != null)
                handler(this, EventArgs.Empty);
        }

        WNetCancelConnection2(_networkName, 0, true);
    }

    #endregion

    #region Private static methods

    /// <summary>
    ///The WNetAddConnection2 function makes a connection to a network resource. The function can redirect a local device to the network resource.
    /// </summary>
    /// <param name="netResource">A <see cref="NetResource"/> structure that specifies details of the proposed connection, such as information about the network resource, the local device, and the network resource provider.</param>
    /// <param name="password">The password to use when connecting to the network resource.</param>
    /// <param name="username">The username to use when connecting to the network resource.</param>
    /// <param name="flags">The flags. See http://msdn.microsoft.com/en-us/library/aa385413%28VS.85%29.aspx for more information.</param>
    /// <returns></returns>
    [DllImport("mpr.dll")]
    private static extern int WNetAddConnection2(NetResource netResource, 
                                                 string password, 
                                                 string username, 
                                                 int flags);

    /// <summary>
    /// The WNetCancelConnection2 function cancels an existing network connection. You can also call the function to remove remembered network connections that are not currently connected.
    /// </summary>
    /// <param name="name">Specifies the name of either the redirected local device or the remote network resource to disconnect from.</param>
    /// <param name="flags">Connection type. The following values are defined:
    /// 0: The system does not update information about the connection. If the connection was marked as persistent in the registry, the system continues to restore the connection at the next logon. If the connection was not marked as persistent, the function ignores the setting of the CONNECT_UPDATE_PROFILE flag.
    /// CONNECT_UPDATE_PROFILE: The system updates the user profile with the information that the connection is no longer a persistent one. The system will not restore this connection during subsequent logon operations. (Disconnecting resources using remote names has no effect on persistent connections.)
    /// </param>
    /// <param name="force">Specifies whether the disconnection should occur if there are open files or jobs on the connection. If this parameter is FALSE, the function fails if there are open files or jobs.</param>
    /// <returns></returns>
    [DllImport("mpr.dll")]
    private static extern int WNetCancelConnection2(string name, int flags, bool force);

    #endregion

    /// <summary>
    /// Finalizes an instance of the <see cref="NetworkConnection"/> class.
    /// Allows an <see cref="System.Object"></see> to attempt to free resources and perform other cleanup operations before the <see cref="System.Object"></see> is reclaimed by garbage collection.
    /// </summary>
    ~NetworkConnection()
    {
        Dispose(false);
    }
}

#region Objects needed for the Win32 functions
#pragma warning disable 1591

/// <summary>
/// The net resource.
/// </summary>
[StructLayout(LayoutKind.Sequential)]
public class NetResource
{
    public ResourceScope Scope;
    public ResourceType ResourceType;
    public ResourceDisplaytype DisplayType;
    public int Usage;
    public string LocalName;
    public string RemoteName;
    public string Comment;
    public string Provider;
}

/// <summary>
/// The resource scope.
/// </summary>
public enum ResourceScope
{
    Connected = 1, 
    GlobalNetwork, 
    Remembered, 
    Recent, 
    Context
} ;

/// <summary>
/// The resource type.
/// </summary>
public enum ResourceType
{
    Any = 0, 
    Disk = 1, 
    Print = 2, 
    Reserved = 8, 
}

/// <summary>
/// The resource displaytype.
/// </summary>
public enum ResourceDisplaytype
{
    Generic = 0x0, 
    Domain = 0x01, 
    Server = 0x02, 
    Share = 0x03, 
    File = 0x04, 
    Group = 0x05, 
    Network = 0x06, 
    Root = 0x07, 
    Shareadmin = 0x08, 
    Directory = 0x09, 
    Tree = 0x0a, 
    Ndscontainer = 0x0b
}
#pragma warning restore 1591
#endregion

Usage:

using(new NetworkConnection(_directoryPath, new NetworkCredential(_userName, _password)))
{
    File.Copy(localPath, _directoryPath);
}
Sauerbraten answered 25/3, 2011 at 14:15 Comment(29)
Where does your EventsHelper come from?Polynices
@mrK: from IDesign. You don't need it, just raise the event as you normally do.Sauerbraten
I know this is a long shot but I figure it can't hurt to ask. I am getting an error thrown out of that class Multiple connections to a server or shared resource by the same user, using more than one user name, are not allowed I disconnected all my network drives and deleted my credentials so I wasn't sure if this error was misleading in some way or if I just need to keep digging through this.Polynices
@mrK: Did you also check for network drives without a drive letter? You can do so, by starting an explorer and navigating to "Tools" -> "Disconnect network drive".Sauerbraten
Yeah and I disconnected all of those too.Polynices
Hm, very strange. What happens, when you try to connect to that share using Windows Explorer?Sauerbraten
Prompts me for creds and when I enter the same ones I'm using for the app, it connects.Polynices
You might try playing with the values assigned to the Scope, ResourceType and DisplayType properties of the NetResource class inside the ctor of NetworkConnection.Sauerbraten
GARRRR I spent the last 5 hours debugging this issue and it turns out I mistyped the password. Now that I fixed it I put this code back to the way it belongs and it works fine. Thanks for all your help.Polynices
Perfect. Thank you. We were trying to map a drive letter to a remote network in an IIS site.. it worked sporadically. This is perfect.Titulary
I get Error 10 The type or namespace name 'GenericEventHandler' could not be found (are you missing a using directive or an assembly reference?)Auriol
how does it work (what is the _directoryPath), if the two computers are NOT part of the same network?Sneakbox
@Serge: What do you mean by "NOT part of the same network"? In any case, _directoryPath is an ordinary UNC path, so \\computer.domain\share\pathSauerbraten
I mean, what if I need to connect to a server named, say "mycomp.cloudapp.net", that I have the Remote Desktop credentials.Sneakbox
@Serge This question and answer are about connecting to a File Share. Remote Desktop is not the topic here, sorry. You might want to ask a new question. And when you do so, please be precise in your problem descriptionSauerbraten
the question is not about remote desktop.. I just connnect to another computer via remote desktop... I would like to do a File Share, but I don't understand if\how the UNC path could be formatted. I have full acces to the remote computer, I know the public IP... Maybe it is possible via the HTTP access?Sneakbox
@Serge: Please, ask a new question. This is no longer about my answer.Sauerbraten
OK. Thanks for your answer. As I can understand, the "remote" UNC path is impossible to build for the computers outside of the local network, so the solution is inappropriate for these cases... I opened a new question about it here: goo.gl/Yq2kmOSneakbox
@Serge That conclusion is incorrect. You can easily build such a path: \\<public IP address of the server>\share\path or \\<dns name of the server>\share\pathSauerbraten
@DanielHilgarth, I have a public IP address X.X.X.X, on that server I have a path D:\shatest that I shared in "READ" for "Everyone", the "\\X.X.X.X\shatest" can't be conected with... (Error 54: The network path was not found)Sneakbox
@Serge There can be multiple reasons for this, one of the more likely ones is a firewall. Not only on the machine itself, but the firewall that is in front of each Amazon VM. The way it sounds, this is now something you should ask on ServerFault. It has nothing to do with C# or development in general. When you are able to access the share from Windows Explorer, but not from your application, that's when you should come back here.Sauerbraten
Hi, I try to use your class in a simple windows login form, I just curious... How do I throw a MessageBox exception when the authentication is failed? It work just fine if the authentication is success.Abomasum
@mutanic: Please ask a new question for this. And in your question, please describe how a Windows Login Form relates to the class I posted.Sauerbraten
@DanielHilgarth, sorry about that...forget my silly question, I suppose to use try catch to achieve that.Abomasum
I see this code all over the internet. Why there is no nuget for that? @DanielHilgarth Can I create a nuget for that?Gemology
@baruchiro: Sure, feel free to do soSauerbraten
Thanks, A very useful class! Seem like I have a problem with connecting to a machine in the domain with domain user. Works great with workgoup and local admin. Any thought what can be a reason for this?Mandeville
Getting error, The type or namespace name 'NetworkCredential' could not be found (are you missing a using directive or an assembly reference?) can someone please help, from where should I import it ?Dyer
@Dyer got the same error and posted a question on it and later found the solution. See #73933713 . Hope you solved it by yourself.Abnormal
G
6

From the code sample on the Daniel Hilgarth's answer, I created a Nuget package that can be consumed so we can maintain the repairs in one place.

Gemology answered 8/2, 2020 at 19:36 Comment(3)
Your Nuget package work's for me. Thanks!!!Suksukarno
github.com/baruchiro/NetworkConnectionGemology
so Im trying to use this in ASP.Net Core V6 .. and getting this error. NetworkConnection is a namespace but is used like a type and using it just like on the git repo.Moller
W
2

you'll need to impersonate the user see this question

Effectivly you'll need to call logon to create windows identity which you can use to access the file system with

there is some more descussion on the subject here

Womera answered 25/3, 2011 at 14:14 Comment(3)
I've actually been fighting with this for a little while. I've used these sites to get something running (I can post code if you like) thescarms.com/dotnet/impersonate.aspx and support.microsoft.com/kb/306158 It seems as though I can't impersonate a user on a remote domain. Maybe I'm doing something wrong. Advice?Polynices
@mrK: Just use the class in my answer, it should work. It uses the same mechanism as windows when you try to access a share in the explorer.Sauerbraten
Just want to jump in here 7 years later. You can't impersonate a user unless it is setup on your computer (workgroup) or your company domain.Parrnell

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