Marshal.PtrToStructure扔AccessViolationException

我有这样的结构：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; 
};

而且我想从文件中读取字节，这些字节复制到使用元帅和的GCHandle上述struct，我的代码是如下：

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();

但我发现了一个AccessViolationException : attempt to read or write protected memory

我不知道为什么这会抛出异常。

来源

2014-10-09 user2140285

我没有立即看到该错误，并编写了一个测试程序来重现问题。使用二进制搜索来查找问题，评论一半的领域了，直到我把范围缩小到：

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

可不行，PInvoke的编组假设默认编组为串是从C字符串，char* 。对于从文件读取的数据，这不可能是正确的，它永远不能包含有效的指针。 AccessViolation在它试图解引用指针时被触发。

在问题中没有提示猜测字符串是如何实际序列化到文件的。该正常方法是：

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

必要时使用十六进制查看器找出SizeConst的正确价值。如果编码不正常（不是系统默认页面），则必须将其声明为byte []并使用正确的编码进行转换。

来源

2014-10-09 11:25:53