.NET 1.1+

Mapping a Drive Letter Programmatically (2)

Some legacy applications do not permit the use of UNC paths when accessing network folders, instead requiring that a drive letter be mapped. When interacting with such software it may be necessary to map a drive letter and later remove mappings using C#.

Defining the NETRESOURCE Structure

The first parameter of WNetAddConnection2, and the second of WNetAddConnection3, accepts a NETRESOURCE structure. This structure contains information relating to the remote resource that you wish to connect to and the drive letter that you want to assign. Before you can use the mapping commands you must declare this structure, ensuring that it exactly matches that expected by the API. To create the structure, add the following:

[StructLayout(LayoutKind.Sequential)]
public struct NETRESOURCE
{
    public uint dwScope;
    public uint dwType;
    public uint dwDisplayType;
    public uint dwUsage;
    public string lpLocalName;
    public string lpRemoteName;
    public string lpComment;
    public string lpProvider;
}

Although the structure defines eight fields, only four of these are required when mapping drive letters. The first, dwType, is used to specify that we want to map to a network folder. This value is always set to a constant value named RESOURCETYPE_DISK. This constant must be defined within the code as follows:

const uint RESOURCETYPE_DISK = 1;

The lpLocalName field holds the drive letter that will be assigned to the mapped path, which is specified in lpRemoteName. The fourth value that must be provided is lpProvider. This string value determines the network provider that will be used to make the connection. However, normally this is set to null to specify that the operating system should automatically determine the provider to use.

Connection Flags

When the connection functions are called, a series of flags can be passed to the command to affect its behaviour. There are six flags, each defined in the table below:

We can create these values in the program by defining the following constants:

const uint CONNECT_UPDATE_PROFILE = 0x1;
const uint CONNECT_INTERACTIVE = 0x8;
const uint CONNECT_PROMPT = 0x10;
const uint CONNECT_REDIRECT = 0x80;
const uint CONNECT_COMMANDLINE = 0x800;
const uint CONNECT_CMD_SAVECRED = 0x1000;