C#

[Serializable]
public struct Dim
{
  public long field1;
  public int field2;
  public string field3;
}
// ...
// Note: it's better to return  your Dim struct instead of using 'out', which
// is basically what you're doing above by using a reference type.
public void FillStruct(out Dim dim)
{
  using (MemoryStream ms = new MemoryStream())
  {
    ms.Write(BitConverter.GetBytes(0L), 0, 8);
    ms.Write(BitConverter.GetBytes(0), 0, 4);
    byte[] buf = Encoding.ANSI.GetBytes("Test");
    ms.Write(buf, 0, buf.Length);

    ms.Seek(0, SeekOrigin.Begin);

    BinaryFormatter formatter = new BinaryFormatter();
    dim = (Dim)formatter.Deserialize(ms);
  }
}

Assembly a = Assembly.LoadFile(@"C:\somedir\dir\some.dll");
if(a != null)
{
    Type[] types = a.GetTypes();
    foreach(Type t in types)
    {
        PropertyInfo[] pia = t.GetProperties();
        MethodInfo[] mia = t.GetMethods();
        FieldInfo[] fia = t.GetFields();
        ConstructorInfo[] cia = t.GetConstructors();
        EventInfo[] eia = t.GetEvents();
        Type[] ia = t.GetInterfaces();
    }
}

typedef char CHAR;
typedef CHAR* LPSTR;
typedef wchar_t WCHAR;
typedef WCHAR* LPWSTR;
#ifdef UNICODE
typedef WCHAR TCHAR;
typedef WCHAR* LPTSTR;
#else
typedef CHAR TCHAR;
typedef CHAR* LPSTR;
#endif

// Note: following is only anexample.
// You can more easily get the computer name by using Environment.MachineName.
[DllImport("user32.dll", CharSet=CharSet.Auto)]
static extern bool GetComputerName([Out] string name, ref int size);

[StructLayout(LayoutKind.Sequential, CharSet=CharSet.Auto)]
public struct Example
{
  public string Field1;
  public string Field2;
  [MarshalAs(UnmanagedType.LPStr)] public string Field3;
}

[DllImport("user.dll", CharSet = CharSet.Unicode)] <br />
int LoginDlg<br />
(<br />
  int    lDSType,<br />
  string lptstrDataSource, <br />
  int    lDSLength,<br />
  string lpctstrUsername, <br />
  string lpctstrPassword,<br />
)

[DllImport("user.dll", CharSet=CharSet.Unicode)]
extern static int LoginDlg(
  int lDSType,
  string lptstrDataSource,
  int lDSLength,
  string lpctstrUsername,
  string lpctstrPassword);