請問各位先進,
C# 可以用 struct 去 mapping 一個 txt file 的一筆 record 嗎?
謝謝!

1.可以
2.不論任何語言都可以
3. 請去看資料結構的書，這種書，書局很多，可以徹底解決你的疑問

===================引 用 carl168 文 章===================
請問各位先進,
C# 可以用 struct 去 mapping 一個 txt file 的一筆 record 嗎?
謝謝!

   好像有點難

Structs have the following properties:

• Structs are value types and classes are reference types.
  
• Unlike classes, structs can be instantiated without using a new operator.
  
• Structs can declare constructors, but they must take parameters.
  
• A struct cannot inherit from another struct or class, and it cannot be the base of a class. All structs inherit directly from System.ValueType, which inherits from System.Object.
  
• A struct can implement interfaces.
  
• A struct can be used as a nullable type and can be assigned a null value.
  

其實也沒有那麼難，在觀念上
只是兩塊記憶體之間的搬移而已．．．

[code cpp]
//---------------------------------------------------------------------------
void __fastcall TForm1::Button1Click(TObject *Sender)
{
struct MyStruct{
char a[2];
char b[3];
char c[4];
char d[5];
char e[6];
char f[7];
};

MyStruct st;

//null-terminated string fields
char *r = "A\0BB\0CCC\0DDDD\0EEEEE\0FFFFFF\0";

memset(&st,0,sizeof(st));
memcpy(&st,(char*)r,sizeof(st));

ListBox1->Clear();
ListBox1->Items->Add(st.a);
ListBox1->Items->Add(st.b);
ListBox1->Items->Add(st.c);
ListBox1->Items->Add(st.d);
ListBox1->Items->Add(st.e);
ListBox1->Items->Add(st.f);


}
//---------------------------------------------------------------------------
[/code]

編輯記錄

C#可以嗎?

可以請問一下?!
(1)
在C#中可以宣告像以下的structure?
其中內含固定長度的資料欄位?

struct MyStruct{
char a[2];
char b[3];
char c[4];
char d[5];
char e[6];
char f[7];
};

(2)在C#中, 有沒有像memcpy()的函式
支援兩塊Buffer互相拷貝?

如果(1), (2)條件皆可滿足,那就可以做得到,
否則只能自行拆解輸入資料到各個structure 的欄位裡了

個人看法, 僅供參考...

===================引 用 HikaruGo 文 章===================
C#可以嗎?

C# 不允許如此宣告

請教各位先進,
C# 真的不能做到這樣的功能嗎?
還是在這裡懂 C# 的先進不多?

使用序列化吧

shieh2700 先進您好,
感謝您的回覆,
但是不太了解您說的序列化,
可否再說得具體一點,
謝謝!

[code c#]
[StructLayout(LayoutKind.Sequential)]
public struct Rec1
{
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 32)]
public string Name;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 64)]
public string Address;
public int Age;
public DateTime Birth;
};
public static class RawData
{
public static byte[] Serialize(object obj)
{
int rawSize = Marshal.SizeOf(obj);
IntPtr buffer = Marshal.AllocHGlobal(rawSize);
Marshal.StructureToPtr(obj, buffer, true);
byte[] result = new byte[rawSize];
Marshal.Copy(buffer, result, 0, rawSize);
Marshal.FreeHGlobal(buffer);
return result;
}
public static T Deserialize(byte[] rawData)
{
Type t = typeof(T);
int rawSize = Marshal.SizeOf(t);
IntPtr buffer = Marshal.AllocHGlobal(rawSize);
Marshal.Copy(rawData, 0, buffer, rawSize);
object result = Marshal.PtrToStructure(buffer, t);
Marshal.FreeHGlobal(buffer);
return (T)result;
}
}
[/code]



可參考下列這篇文章:
http://huanlin.dyndns.org/cs/blogs/huan-lins_blog/archive/2007/10/30/obfuscator-and-serialization.aspx

&

http://211.147.225.34/gate/big5/dotnet.chinaitlab.com/CSharp/735779.html

編輯記錄