[英]How do we dynamically change the assembly path in DLLImport attribute?
我們如何在if條件語句中更改DLLImport屬性中的程序集路徑? 我想做這樣的事情:
string serverName = GetServerName();
if (serverName == "LIVE")
{
DLLImportString = "ABC.dll";
}
else
{
DLLImportString = "EFG.dll";
}
DllImport[DLLImportString]
您無法設置在運行時計算的屬性值
您可以使用diff DllImports
定義兩個方法,並在if語句中調用它們
DllImport["ABC.dll"]
public static extern void CallABCMethod();
DllImport["EFG.dll"]
public static extern void CallEFGMethod();
string serverName = GetServerName();
if (serverName == "LIVE")
{
CallABCMethod();
}
else
{
CallEFGMethod();
}
或者您可以嘗試使用winapi LoadLibrary加載dll dynamicaly
[DllImport("kernel32.dll", EntryPoint = "LoadLibrary")]
static extern int LoadLibrary([MarshalAs(UnmanagedType.LPStr)] string lpLibFileName);
[DllImport("kernel32.dll", EntryPoint = "GetProcAddress")]
static extern IntPtr GetProcAddress( int hModule,[MarshalAs(UnmanagedType.LPStr)] string lpProcName);
[DllImport("kernel32.dll", EntryPoint = "FreeLibrary")]
static extern bool FreeLibrary(int hModule);
創建適合dll方法的委托
delegate void CallMethod();
然后嘗試使用類似的東西
int hModule = LoadLibrary(path_to_your_dll); // you can build it dynamically
if (hModule == 0) return;
IntPtr intPtr = GetProcAddress(hModule, method_name);
CallMethod action = (CallMethod)Marshal.GetDelegateForFunctionPointer(intPtr, typeof(CallMethod));
action.Invoke();
您需要通過LoadLibrary / GetProcAddress手動加載DLL。
我對小應用程序有同樣的需求並使用了c ++ / cli。
在c#中它看起來像:
delegate int MyFunc(int arg1, [MarshalAs(UnmanagedType.LPStr)]String arg2);
public static void Main(String[] args)
{
IntPtr mydll = LoadLibrary("mydll.dll");
IntPtr procaddr = GetProcAddress(mydll, "Somfunction");
MyFunc myfunc = Marshal.GetDelegateForFunctionPointer(procaddr, typeof(MyFunc));
myfunc(1, "txt");
}
編輯: 這是完整的例子
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