Marshal.PtrToStructure扔AccessViolationException

我有這樣的結構：Marshal.PtrToStructure扔AccessViolationException

[StructLayout(LayoutKind.Sequential)] 
    public struct IS 
    { 
    public UInt32 ID; 
    public UInt32 Quality; 
    public UInt32 Flags; 
    public UInt32 Flags2;  
    public UInt32 ContainerSlots; 
    [MarshalAs(UnmanagedType.ByValArray, SizeConst = 10)] 
    public Int32[] ItemStatType; 
    [MarshalAs(UnmanagedType.ByValArray, SizeConst = 10)] 
    public UInt32[] ItemStatValue;  
    [MarshalAs(UnmanagedType.ByValArray, SizeConst = 10)] 
    public Int32[] ItemStatUnk1;  
    [MarshalAs(UnmanagedType.ByValArray, SizeConst = 10)] 
    public Int32[] ItemStatUnk2;  
    public UInt32 ScalingStatDistribution; 
    public UInt32 DamageType;  
    public UInt32 Delay;  
    public float RangedModRange; 
    [MarshalAs(UnmanagedType.ByValArray, SizeConst = 5)] 
    public Int32[] SpellId;   
    [MarshalAs(UnmanagedType.ByValArray, SizeConst = 5)] 
    public Int32[] SpellTrigger;  
    [MarshalAs(UnmanagedType.ByValArray, SizeConst = 5)] 
    public Int32[] SpellCharges; 
    [MarshalAs(UnmanagedType.ByValArray, SizeConst = 5)] 
    public Int32[] SpellCooldown; 
    [MarshalAs(UnmanagedType.ByValArray, SizeConst = 5)] 
    public Int32[] SpellCategory;  
    [MarshalAs(UnmanagedType.ByValArray, SizeConst = 5)] 
    public Int32[] SpellCategoryCooldown; 
    public UInt32 Bonding; 
    public string Name;  
    public string Name2;     
    public string Name3;   
    [MarshalAs(UnmanagedType.ByValArray, SizeConst = 3)] 
    public UInt32[] Color; 
    [MarshalAs(UnmanagedType.ByValArray, SizeConst = 3)] 
    public UInt32[] Content; 
};

而且我想從文件中讀取字節，這些字節複製到使用元帥和的GCHandle上述struct，我的代碼是如下：

reader = BinaryReader.FromFile(fileName); 
m_rows = new List<IS>(); 
int size = Marshal.SizeOf(typeof(IS)); 
if(reader.BaseStream.Length < size) 
    return; 
byte[] buffer = new byte[size]; 
buffer = reader.ReadBytes(size); 
GCHandle handle = GCHandle.Alloc(buffer, GCHandleType.Pinned); 
m_rows.Add((IS)Marshal.PtrToStructure(handle.AddrOfPinnedObject(), typeof(IS))); 
handle.Free();

但我發現了一個AccessViolationException : attempt to read or write protected memory

我不知道爲什麼這會拋出異常。

來源

2014-10-09 user2140285

我沒有立即看到該錯誤，並編寫了一個測試程序來重現問題。使用二進制搜索來查找問題，評論一半的領域了，直到我把範圍縮小到：

[StructLayout(LayoutKind.Sequential)] 
public struct IS { 
    public string Name; 
}

可不行，PInvoke的編組假設默認編組爲串是從C字符串，char* 。對於從文件讀取的數據，這不可能是正確的，它永遠不能包含有效的指針。 AccessViolation在它試圖解引用指針時被觸發。

在問題中沒有提示猜測字符串是如何實際序列化到文件的。該正常方法是：

[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Ansi)] 
public struct IS { 
    [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 42)] 
    public string Name; 
};

必要時使用十六進制查看器找出SizeConst的正確價值。如果編碼不正常（不是系統默認頁面），則必須將其聲明爲byte []並使用正確的編碼進行轉換。

來源

2014-10-09 11:25:53