C#

Declare Sub neededFunciton Lib "UnmanagedDLL.dll" (ByRef nestedStruc As NESTED_STRUC_TYPE)

Public Type NESTED_STRUC_TYPE
    iNum1 As Long  
    fNum2(coniMaxSize) As Single
    nextNestedStruc As NEXT_NESTED_STRUC_TYPE   .
End Type

Public Type NEXT_NESTED_STRUC_TYPE
    iAnotherNum1 As Long
    fAnotherNum2(coniMaxSize) As Single    
    THIRDNestedStruc As THIRD_NESTED_STRUC_TYPE
End Type

Public Type THIRD_NESTED_STRUC_TYPE
    fArray1(coniMaxSize) As Single   
    fArray2(coniMaxSize) As Single 
    fArray3(coniMaxSize) As Single
    fArray4(coniMaxSize) As Single 
End Type

Public Const coniMaxSize As Integer = 144

[DllImport(@"C:\WINDOWS\UnmanagedDLL.dll", EntryPoint = "NeededFunciton")]
internal static extern int neededFunciton(ref NESTED_STRUC_TYPE nestedStruc);

[DllImport("kernel32.dll", SetLastError=true)]
public static extern IntPtr LoadLibrary(string dllToLoad);
[DllImport("kernel32.dll", SetLastError = true)]
public static extern IntPtr GetProcAddress(IntPtr hModule, string procedureName);
[DllImport("kernel32.dll", SetLastError = true)]
public static extern bool FreeLibrary(IntPtr hModule);
[UnmanagedFunctionPointer(CallingConvention.Cdecl)]
private delegate BigObject MyDelegate(ref BigObject.NESTED_STRUC_TYPE nestedStruc);


internal int NeededFunciton(ref NESTED_STRUC_TYPE nestedStruc)
{
    // Call LoadLibrary and GetProcAddress to get the address of the function
    // within the UnmanagedDLL.dll

    // LoadLibrary - returns a handle to the UnmanagedDLL.dll
    IntPtr pDll = LoadLibrary(@"C:\WINDOWS\UnmanagedDLL.dll");
    if (pDll != IntPtr.Zero)
    {
    // GetProcAddress - obtain the address of an exported function within
    // the previously loaded dll
    IntPtr pAddressOfFunctionToCall = GetProcAddress(pDll, "NeededFunciton");
    if (pAddressOfFunctionToCall != IntPtr.Zero)
    {
        // Now use the GetDelegateForFunctionPointer static method within the Marshal class
        // to assign this address to a predefined C# delegate
        MyDelegate myDelegate = (MyDelegate)Marshal.GetDelegateForFunctionPointer(
        pAddressOfFunctionToCall,
        typeof(MyDelegate));
        try
        {
        myDelegate(ref nestedStruc);
        }
        catch (Exception e)
        {
       
        //todo, changed exception
        }
    }
    }
    return Convert.ToInt16 (FreeLibrary(pDll));
}

bigObject.NeededFunciton(ref nestedStruc);