C# Signature:

using DWORD = System.UInt32;
using ULONG = System.UInt64;

[DllImport(Netapi32, CharSet=CharSet.Auto, SetLastError=true)]
internal static extern DWORD DsGetDcOpen(
     [MarshalAs(UnmanagedType.LPTStr)]
     string DnsName,
     ULONG OptionFlags,
     [MarshalAs(UnmanagedType.LPTStr)]
     string SiteName,
     IntPtr DomainGuid,
     [MarshalAs(UnmanagedType.LPTStr)]
     string DnsForestName,
     ULONG DcFlags,
     out IntPtr RetGetDcContext
     );

For Example 1 below:

[DllImport("Netapi32.dll", EntryPoint = "DsGetDcOpenW", CallingConvention = CallingConvention.StdCall, CharSet = CharSet.Unicode)]
internal static extern int DsGetDcOpen(
    [In] string dnsName,
    [In] int optionFlags,
    [In] string siteName,
    [In] IntPtr domainGuid,
    [In] string dnsForestName,
    [In] int dcFlags,
    out IntPtr retGetDcContext
    );

VB Signature:

Declare Function DsGetDcOpen Lib "netapi32.dll" (TODO) As TODO

User-Defined Types:

None.

Notes:

RetGetDcContext

out Pointer to a HANDLE value that receives the domain controller enumeration context handle. This handle is used with the DsGetDcNext function to identify the domain controller enumeration operation. This handle is passed to DsGetDcClose to close the domain controller enumeration operation.

Tips & Tricks:

Please add some!

Sample Code:

    IntPtr pDcContext = new IntPtr();
    int iReturn = 0;

    // if you are getting the entire domain
    iReturn = DsGetDcOpen("domain1.mydomains.com", 0, null, (System.IntPtr)null, null, 0, out pDcContext);

    // this is a great call, it will give you all the DC's that COVER a site, not just the DC's in that site:
    iReturn = DsGetDcOpen("domain1.mydomains.com", 1, "MYADSITE", (System.IntPtr)null, null, 0, out pDcContext);

Alternative Managed API:

Do you know one? Please contribute it!