c# - 我们如何动态更改 DLLImport 属性中的程序集路径？

Question

我们如何在 if 条件语句中更改 DLLImport 属性中的程序集路径？例如我想做这样的事情:

string serverName = GetServerName();
if (serverName == "LIVE")
{
   DLLImportString = "ABC.dll";

}
else
{
DLLImportString = "EFG.dll";
}

DllImport[DLLImportString]

Answer 1

你不能设置在运行时计算的属性值

您可以使用 diff DllImports 定义两个方法并在您的 if 语句中调用它们

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();
}

或者你可以试试用winapi LoadLibrary动态加载dll

[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);

创建适合dll中方法的委托(delegate)

delegate void CallMethod();

然后尝试使用类似的东西

   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();