[C#]快速將字串轉換為結構
看到MSDN上請問將一個字串copy到一個結構中最快的方式為何?這篇的發問，做些紀錄：
要將字串快速轉換為結構，首先我們必須要在結構上加些Attribute，像是設定每個欄位所佔用的型態、大小...等：
[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
public struct MyStruct
{
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 4)]
public string fname;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 4)]
public string lname;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 7)]
public string phone;
}
在轉換時先透過Marshal.StringToBSTR將字串轉為指標，再透過Marshal.PtrToStructure將指標轉換為指定的結構型態，最後再用Marshal.FreeBSTR把剛剛的指標位置給釋放掉就可以了：
private static T ConvertToStruct<T>(string val)
{
IntPtr valPoint = Marshal.StringToBSTR(val);
T ret = (T)Marshal.PtrToStructure(valPoint, typeof(T));
Marshal.FreeBSTR(valPoint);
return ret;
}
完整範例如下：
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.IO;
using System.Runtime.InteropServices;
namespace ConsoleApplication20
{
class Program
{
[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
public struct MyStruct
{
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 4)]
public string fname;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 4)]
public string lname;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 7)]
public string phone;
}
private static T ConvertToStruct<T>(string val)
{
IntPtr valPoint = Marshal.StringToBSTR(val);
T ret = (T)Marshal.PtrToStructure(valPoint, typeof(T));
Marshal.FreeBSTR(valPoint);
return ret;
}
public static void Main()
{
MyStruct ms = ConvertToStruct<MyStruct>("abcdefgh2223333");
Console.WriteLine("fname is: {0}", ms.fname);
Console.WriteLine("lname is: {0}", ms.lname);
Console.WriteLine("phone is: {0}", ms.phone);
}
}
}
運行後可以發現abcdefgh2223333字串會依照我們在結構欄位所設定的長度自動填入：
