Question

我见过几个关于这个问题的问题。例如：

"Object can be disposed of more than once" error

但我无法弄清楚我应该对我的代码做些什么。我从代码分析中得到的警告是：

1＆gt; D：\ My Programs \ 2017 \ PTSTools \ PTSTools \ PTSTools.cs（81）：警告 CA2202：Microsoft.Usage：对象'iCrypt'可以处理多个一次在方法'PTSToolsClass.Crypt（string，string，bool）'中。避免生成一个不应该调用的System.ObjectDisposedException 在物体上多次处理：线条：81

有问题的方法：

private string Crypt(string strData, string strPassword, bool bEncrypt)
{
    byte[] u8Salt = new byte[] { ... };

    PasswordDeriveBytes iPass = new PasswordDeriveBytes(strPassword, u8Salt);

    Rijndael iAlg = Rijndael.Create();
    iAlg.Key = iPass.GetBytes(32);
    iAlg.IV = iPass.GetBytes(16);

    ICryptoTransform iTrans = (bEncrypt) ? iAlg.CreateEncryptor() : iAlg.CreateDecryptor();

    MemoryStream iMem = new MemoryStream();
    CryptoStream iCrypt = new CryptoStream(iMem, iTrans, CryptoStreamMode.Write);

    byte[] u8Data;
    if (bEncrypt)
        u8Data = Encoding.Unicode.GetBytes(strData);
    else
        u8Data = Convert.FromBase64String(strData);

    try
    {
        iCrypt.Write(u8Data, 0, u8Data.Length);
        iCrypt.Close();
        if (bEncrypt)
            return Convert.ToBase64String(iMem.ToArray());
        else
            return Encoding.Unicode.GetString(iMem.ToArray());
    }
    catch
    {
        return null;
    }
    finally
    {
        iCrypt.Close();
    }
}

有人可以解释为什么我会针对finally代码行提出此警告吗？

谢谢。

更新

根据评论，我将其更改为：

private string Crypt(string strData, string strPassword, bool bEncrypt)
{
    byte[] u8Salt = new byte[] { ... };

    PasswordDeriveBytes iPass = new PasswordDeriveBytes(strPassword, u8Salt);

    Rijndael iAlg = Rijndael.Create();
    iAlg.Key = iPass.GetBytes(32);
    iAlg.IV = iPass.GetBytes(16);

    ICryptoTransform iTrans = (bEncrypt) ? iAlg.CreateEncryptor() : iAlg.CreateDecryptor();

    MemoryStream iMem = new MemoryStream();
    using (CryptoStream iCrypt = new CryptoStream(iMem, iTrans, CryptoStreamMode.Write))
    {
         byte[] u8Data;
        if (bEncrypt)
            u8Data = Encoding.Unicode.GetBytes(strData);
        else
            u8Data = Convert.FromBase64String(strData);

        try
        {
            iCrypt.Write(u8Data, 0, u8Data.Length);
            iCrypt.Close();
            if (bEncrypt)
                return Convert.ToBase64String(iMem.ToArray());
            else
                return Encoding.Unicode.GetString(iMem.ToArray());
        }
        catch
        {
            return null;
        }
    }
}

但我现在有这些警告：

1>D:\My Programs\2017\PTSTools\PTSTools\PTSTools.cs(77): warning CA2202: Microsoft.Usage : Object 'iCrypt' can be disposed more than once in method 'PTSToolsClass.Crypt(string, string, bool)'. To avoid generating a System.ObjectDisposedException you should not call Dispose more than one time on an object.: Lines: 77
1>D:\My Programs\2017\PTSTools\PTSTools\PTSTools.cs(77): warning CA2202: Microsoft.Usage : Object 'iMem' can be disposed more than once in method 'PTSToolsClass.Crypt(string, string, bool)'. To avoid generating a System.ObjectDisposedException you should not call Dispose more than one time on an object.: Lines: 77

它现在不喜欢catch块。

更新

理解为：

   private string Crypt(string strData, string strPassword, bool bEncrypt)
    {
        byte[] u8Salt = new byte[] { 0x26, 0x19, 0x81, 0x4E, 0xA0, 0x6D, 0x95, 0x34, 0x26, 0x75, 0x64, 0x05, 0xF6 };

        PasswordDeriveBytes iPass = new PasswordDeriveBytes(strPassword, u8Salt);

        Rijndael iAlg = Rijndael.Create();
        iAlg.Key = iPass.GetBytes(32);
        iAlg.IV = iPass.GetBytes(16);

        ICryptoTransform iTrans = (bEncrypt) ? iAlg.CreateEncryptor() : iAlg.CreateDecryptor();

        MemoryStream iMem = new MemoryStream();
        using (CryptoStream iCrypt = new CryptoStream(iMem, iTrans, CryptoStreamMode.Write))
        {
                byte[] u8Data;
            if (bEncrypt)
                u8Data = Encoding.Unicode.GetBytes(strData);
            else
                u8Data = Convert.FromBase64String(strData);

            try
            {
                iCrypt.Write(u8Data, 0, u8Data.Length);
                if (bEncrypt)
                    return Convert.ToBase64String(iMem.ToArray());
                else
                    return Encoding.Unicode.GetString(iMem.ToArray());
            }
            catch
            {
                return null;
            }
        }
    }

Answer 1

Because the finally block of a try-(catch-)finally block is always executed，分析师看到了这一点：

try
{
    iCrypt.Close();
}
finally
{
    iCrypt.Close();
}

然后正确地推断这些调用可以连续发生，导致ObjectDisposedException在第二次调用中被抛出。

所以：您不需要iCrypt.Close()块中的try，因为它始终会在finally中关闭，无论是否发生异常。

Answer 2

您正在调用iCrypt.Close（）;两次，从try语句中删除调用，你会没事的。

Answer 3

来自代码分析的消息很清楚。您的代码处理（关闭）iCrypt两次。一次在try块内，一次在finally块中。移除try块中的iCrypt.Close();行（iCrypt.Write(...)和if(...)之间，警告将消失。

更好的approch是一个使用块：

using (CryptoStream iCrypt = new CryptoStream(...)) {
   .... // your code without the finally block
}

无论是否在块内抛出异常，using都将调用iCrypt.Close（）。

对象'iCrypt'可以被多次处理

3 个答案: