C＃运算符'+'不能应用于类型'IntPtr'和'int'的操作数

Question

I'm not a big connoisseur of C #. I would be very grateful if anyone could help me with this:

I have the function of recovering the "log \\ password" from the Windows store.

If I compile in a .Net 4.0 environment, then everything is fine and everything works.

But I would like to make this function and the program as a whole for .Net 3.5 and here I get an error in these lines:

var vaultIdPtr = vaultGuids + i * Marshal.SizeOf(typeof(Guid));

var itemPtr = items + i * Marshal.SizeOf(typeof(VAULT_ITEM_W8));

and so on

CS0019 C# Operator '+' cannot be applied to operands of type 'IntPtr' and 'int'

 public static List<RecoveredAccount> ReadVaultPasswords()
    {

        List<RecoveredAccount> ReadVault = new List<RecoveredAccount>();

        if (!(Environment.OSVersion.Version.Major > 6 || (Environment.OSVersion.Version.Major == 6 && Environment.OSVersion.Version.Minor >= 1)))
        {
            // continue;
        }

        // var Vault_WebCredential_ID = Guid.Parse("3CCD5499-87A8-4B10-A215-608888DD3B55");

        Guid Vault_WebCredential_ID = new Guid("3CCD5499-87A8-4B10-A215-608888DD3B55");

        const uint ERROR_SUCCESS = 0;
        const uint VAULT_ENUMERATE_ALL_ITEMS = 512;

        bool isWin8 = Environment.OSVersion.Version.Major == 6 && Environment.OSVersion.Version.Minor > 1;

        int vaultCount;
        IntPtr vaultGuids = IntPtr.Zero;
        try
        {
            if (VaultEnumerateVaults(0, out vaultCount, out vaultGuids) == ERROR_SUCCESS)
            {
                for (var i = 0; i < vaultCount; ++i)
                {
                    IntPtr vault = IntPtr.Zero;
                    try
                    {
                        var vaultIdPtr = vaultGuids + i * Marshal.SizeOf(typeof(Guid));


                        if (VaultOpenVault(vaultIdPtr, 0, out vault) == ERROR_SUCCESS)
                        {
                            int itemCount;
                            IntPtr items = IntPtr.Zero;
                            try
                            {
                                if (VaultEnumerateItems(vault, VAULT_ENUMERATE_ALL_ITEMS, out itemCount, out items) == ERROR_SUCCESS)
                                {
                                    for (var j = 0; j < itemCount; ++j)
                                    {
                                        string host;
                                        string username;
                                        string password = string.Empty;
                                        DateTime date = DateTime.Now;
                                        if (isWin8)
                                        {
                                            var itemPtr = items + i * Marshal.SizeOf(typeof(VAULT_ITEM_W8));


                                            var item = (VAULT_ITEM_W8)Marshal.PtrToStructure(itemPtr, typeof(VAULT_ITEM_W8));
                                            if (!Vault_WebCredential_ID.Equals(new Guid(item.SchemaId)))
                                            {
                                                continue;
                                            } ...etc


    [DllImport(VAULTCLI_DLL, CallingConvention = CallingConvention.StdCall)]
    private static extern uint VaultEnumerateVaults(uint dwFlags, out int VaultsCount, out IntPtr ppVaultGuids);

    [DllImport(VAULTCLI_DLL, CallingConvention = CallingConvention.StdCall)]
    private static extern uint VaultEnumerateItems(IntPtr pVaultHandle, uint dwFlags, out int ItemsCount, out IntPtr ppItems);

    [DllImport(VAULTCLI_DLL, CallingConvention = CallingConvention.StdCall, EntryPoint = "VaultGetItem")]
    private static extern uint VaultGetItem7(IntPtr pVaultHandle, IntPtr pSchemaId, IntPtr pResource, IntPtr pIdentity, IntPtr hwndOwner, uint dwFlags, out IntPtr ppItems);

    [DllImport(VAULTCLI_DLL, CallingConvention = CallingConvention.StdCall, EntryPoint = "VaultGetItem")]
    private static extern uint VaultGetItem8(IntPtr pVaultHandle, IntPtr pSchemaId, IntPtr pResource, IntPtr pIdentity, IntPtr pPackageSid, IntPtr hwndOwner, uint dwFlags, out IntPtr ppItems);

    [DllImport(VAULTCLI_DLL, CallingConvention = CallingConvention.StdCall)]
    private static extern uint VaultOpenVault(IntPtr pVaultId, uint dwFlags, out IntPtr pVaultHandle);

    [DllImport(VAULTCLI_DLL, CallingConvention = CallingConvention.StdCall)]
    private static extern uint VaultCloseVault(IntPtr pVaultHandle);

    [DllImport(VAULTCLI_DLL, CallingConvention = CallingConvention.StdCall)]
    private static extern uint VaultFree(IntPtr pMemory);

Answer 1

If you look at the source for IntPtr for version 4.7.2( https://referencesource.microsoft.com/#mscorlib/system/intptr.cs ) you'll see that there's an implementation of the operator +

public static IntPtr operator +(IntPtr pointer, int offset) 
    {
        #if WIN32
            return new IntPtr(pointer.ToInt32() + offset);
        #else
            return new IntPtr(pointer.ToInt64() + offset);
        #endif
    }

I can't find the implementation for the version 3.5, but I guess that this operator is not implemented in earlier versions.

You can make it work using the code for the operator +, like this:

    static void Main(string[] args)
    {
        IntPtr vaultGuids = IntPtr.Zero;
        int i = 10;

// Works in .net 4.0
        var vauldIdPtr = vaultGuids + i * Marshal.SizeOf(typeof(Guid));
        Console.WriteLine(vauldIdPtr);

// works in .net 4.0 and 3.5
        var ptr2 = new IntPtr(vaultGuids.ToInt32() + i * Marshal.SizeOf(typeof(Guid)));
        Console.WriteLine(ptr2);
    }