在单个数据块中包含不同类型变量的最佳方法是什么？ [英] What is the best way to contain different types of variables in a single blob of data?
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问题描述
大家好：
我正在创建一个工作表应用程序。有一组共同的字段（即名称，出生日期，一些文本字段等）然后有一个代码会提出一系列问题。
每个代码可以有不同的问题，可以有不同的类型（即字符串，整数，浮点数等）
所以我想是有一个名称，生日和代码作为文件密钥的数据库，以及一个4096字节的blob（任何代码的字段数都不能超过这个大小）。
我正在为属于代码的每组问题创建结构，并将它们复制进出blob，但它似乎不起作用。无论我尝试什么，我都会尝试写入受保护的代码错误，或者信息显示为乱码，或者最新的信息，不能作为非托管结构进行编组;不能计算有意义的大小或偏移量。
最好的方法是什么？我的一个示例'代码'结构如下：
Hello all:
I am creating a worksheet application. There is a common set of fields (i.e. name, Birthdate, some text fields, etc.) Then there is a 'code' that brings up a set of questions.
Each code can have a different amount of questions, and could have different types (i.e. string, int, float, etc.)
So what I figured is to have a Database with the name, birthdate, and code as the key to the file, and a 4096 byte 'blob' (no amount of fields for any code can go over this size).
I was creating 'structs' for each set of questions that belong to a code, and copying them in and out of the 'blob', but it doesn't seem to be working. No matter what I try, I get either 'attempting to write to protected code' errors, or the information appears garbled, or the newest one, "cannot be marshaled as an unmanaged structure; no meaningful size or offset can be computed."
What is the best way to do this? One of my example 'code' structs is below:
public partial class Code1 : Form
{
private new frmMain ParentForm;
private Code1_Record ws = new Code1_Record();
public Code1(frmMain _parent, byte[] _record)
{
InitializeComponent();
ParentForm = _parent;
if (_record != null)
{
LoadData(_record);
}
}
private void LoadData(byte[] _record)
{
//int iSize = Marshal.SizeOf(ws);
//byte[] bTmp = new byte[iSize];
//Array.Copy(_record, 0, bTmp, 0, iSize);
ws = FromBytes(_record);
tbxL_CFA.Text = ws.fL_CFA;
tbxL_SFAprox.Text = ws.fL_SFAprox;
tbxL_SFAmid.Text = ws.fL_SFAmid;
tbxL_SFAdistal.Text = ws.fL_SFAdistal;
tbxL_POP.Text = ws.fL_POP;
tbxL_PTA.Text = ws.fL_PTA;
tbxL_DPA.Text = ws.fL_DPA;
chbL_CFA.Checked = ws.bL_CFA;
chbL_SFAprox.Checked = ws.bL_SFAprox;
chbL_SFAmid.Checked = ws.bL_SFAmid;
chbL_SFAdistal.Checked = ws.bL_SFAdistal;
chbL_POP.Checked = ws.bL_POP;
chbL_PTA.Checked = ws.bL_PTA;
chbL_DPA.Checked = ws.bL_DPA;
tbxR_CFA.Text = ws.fR_CFA;
tbxR_SFAprox.Text = ws.fR_SFAprox;
tbxR_SFAmid.Text = ws.fR_SFAmid;
tbxR_SFAdistal.Text = ws.fR_SFAdistal;
tbxR_POP.Text = ws.fR_POP;
tbxR_PTA.Text = ws.fR_PTA;
tbxR_DPA.Text = ws.fR_DPA;
chbR_CFA.Checked = ws.bR_CFA;
chbR_SFAprox.Checked = ws.bR_SFAprox;
chbR_SFAmid.Checked = ws.bR_SFAmid;
chbR_SFAdistal.Checked = ws.bR_SFAdistal;
chbR_POP.Checked = ws.bR_POP;
chbR_PTA.Checked = ws.bR_PTA;
chbR_DPA.Checked = ws.bR_DPA;
}
private void btnSave_Click(object sender, EventArgs e)
{
ws.fL_CFA = tbxL_CFA.Text;
ws.fL_SFAprox = tbxL_SFAprox.Text;
ws.fL_SFAmid = tbxL_SFAmid.Text;
ws.fL_SFAdistal = tbxL_SFAdistal.Text;
ws.fL_POP = tbxL_POP.Text;
ws.fL_PTA = tbxL_PTA.Text;
ws.fL_DPA = tbxL_DPA.Text;
ws.bL_CFA = chbL_CFA.Checked;
ws.bL_SFAprox = chbL_SFAprox.Checked;
ws.bL_SFAmid = chbL_SFAmid.Checked;
ws.bL_SFAdistal = chbL_SFAdistal.Checked;
ws.bL_POP = chbL_POP.Checked;
ws.bL_PTA = chbL_PTA.Checked;
ws.bL_DPA = chbL_DPA.Checked;
ws.fR_CFA = tbxR_CFA.Text;
ws.fR_SFAprox = tbxR_SFAprox.Text;
ws.fR_SFAmid = tbxR_SFAmid.Text;
ws.fR_SFAdistal = tbxR_SFAdistal.Text;
ws.fR_POP = tbxR_POP.Text;
ws.fR_PTA = tbxR_PTA.Text;
ws.fR_DPA = tbxR_DPA.Text;
ws.bR_CFA = chbR_CFA.Checked;
ws.bR_SFAprox = chbR_SFAprox.Checked;
ws.bR_SFAmid = chbR_SFAmid.Checked;
ws.bR_SFAdistal = chbR_SFAdistal.Checked;
ws.bR_POP = chbR_POP.Checked;
ws.bR_PTA = chbR_PTA.Checked;
ws.bR_DPA = chbR_DPA.Checked;
ws.bPlaque = chbPlaque.Checked;
ws.sLocation = tbxLocation.Text;
ParentForm.CloseExamForm(ToBytes(ws));
this.Close();
}
private void btnClose_Click(object sender, EventArgs e)
{
// Check to see if any data changed
ParentForm.CloseExamForm(null);
this.Close();
}
#region Record Layout and Methods to and from byte[]
[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
private struct Code1_Record
{
//Left Measurements
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 6)]
public string fL_CFA;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 6)]
public string fL_SFAprox;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 6)]
public string fL_SFAmid;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 6)]
public string fL_SFAdistal;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 6)]
public string fL_POP;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 6)]
public string fL_PTA;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 6)]
public string fL_DPA;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 6)]
//Left 'Abnormal' (true/false)
public bool bL_CFA;
public bool bL_SFAprox;
public bool bL_SFAmid;
public bool bL_SFAdistal;
public bool bL_POP;
public bool bL_PTA;
public bool bL_DPA;
//Right Measurements
public string fR_CFA;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 6)]
public string fR_SFAprox;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 6)]
public string fR_SFAmid;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 6)]
public string fR_SFAdistal;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 6)]
public string fR_POP;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 6)]
public string fR_PTA;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 6)]
public string fR_DPA;
//Right 'Abnormal' (true/false)
public bool bR_CFA;
public bool bR_SFAprox;
public bool bR_SFAmid;
public bool bR_SFAdistal;
public bool bR_POP;
public bool bR_PTA;
public bool bR_DPA;
//Plaque
public bool bPlaque;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 256)]
public string sLocation;
}
private byte[] ToBytes(Code1_Record str)
{
int size = Marshal.SizeOf(str);
byte[] arr = new byte[size];
IntPtr ptr = Marshal.AllocHGlobal(size);
Marshal.StructureToPtr(str, ptr, true);
Marshal.Copy(ptr, arr, 0, size);
Marshal.FreeHGlobal(ptr);
return arr;
}
private Code1_Record FromBytes(byte[] arr)
{
Code1_Record str = new Code1_Record();
int size = Marshal.SizeOf(str);
IntPtr ptr = Marshal.AllocHGlobal(size);
Marshal.Copy(arr, 0, ptr, size);
str = (Code1_Record)Marshal.PtrToStructure(ptr, str.GetType());
Marshal.FreeHGlobal(ptr);
return str;
}
}
#endregion
请您提前帮助我。
Thak you very much in advance for helping me.
推荐答案
最好的方法是没有不同类型的变量甚至blob中相同类型的不同变量。它会破坏关系模型的目的。
但在极少数情况下你真的可以从这种方法中受益（很难，但我不想再进一步讨论），方法可能是序列化：
http://en.wikipedia.org/wiki/Serialization [ ^ ]，
https://msdn.microsoft.com/en-us/library/ms973893.aspx [ ^ ]，
https://msdn.microsoft.com/en-us/library/7ay27kt9%28v=vs.110%29.aspx [ ^ ]，
https://msdn.microsoft.com/en-us/library/ms733127%28v=vs .110％29.aspx [ ^ ]（最强大，一致且易于使用的序列化方法）。
-SA
The best way is not having "different types of variables" or even different variables of the same type in a blob. It would defeat the purpose of the relational model.
But in rare cases you really can benefit from this approach (hardly, but I don't want to discuss it any further), the approach could be serialization:
http://en.wikipedia.org/wiki/Serialization[^],
https://msdn.microsoft.com/en-us/library/ms973893.aspx[^],
https://msdn.microsoft.com/en-us/library/7ay27kt9%28v=vs.110%29.aspx[^],
https://msdn.microsoft.com/en-us/library/ms733127%28v=vs.110%29.aspx[^] (most robust, consistent and easy to use serialization approach).
—SA
谢谢 - 序列化做了我想要的：
Thank you - Serialization did what I wanted:
private byte[] ObjectToByteArray(Object obj)
{
if (obj == null)
return null;
BinaryFormatter bf = new BinaryFormatter();
using (MemoryStream ms = new MemoryStream())
{
bf.Serialize(ms, obj);
return ms.ToArray();
}
}
private Object ByteArrayToObject(byte[] bArray)
{
if (bArray == null)
return null;
BinaryFormatter bf = new BinaryFormatter();
using (MemoryStream ms = new MemoryStream(bArray))
{
return bf.Deserialize(ms);
}
}
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