blocks|key|682844|text|只要DllImport位于系统路径上的某个位置，就可以在没有指定完整路径的情况下正常工作。您可以临时将用户的文件夹添加到路径中。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|682845|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

DllImport will work fine without the complete path specified as long as the dll is located somewhere on the system path. You may be able to temporarily add the user's folder to the path.

blocks|key|682872|text|如果所有操作都失败，只需将DLL放在windows\system32文件夹中。编译器会找到它的。使用：DllImport("user32.dll"...指定要加载的DLL，设置EntryPoint+=+"my_unmanaged_function"以将所需的非托管函数导入到您的C#应用程序中：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|682873|+using+System;
using+System.Runtime.InteropServices;

class+Example
{
+++//+Use+DllImport+to+import+the+Win32+MessageBox+function.

+++[DllImport+("user32.dll",+CharSet+=+CharSet.Auto)]
+++public+static+extern+int+MessageBox+
++++++(IntPtr+hWnd,+String+text,+String+caption,+uint+type);

+++static+void+Main()
+++{
++++++//+Call+the+MessageBox+function+using+platform+invoke.
++++++MessageBox+(new+IntPtr(0),+"Hello,+World!",+"Hello+Dialog",+0);++++
+++}
}|code-block|syntax|javascript|682874|源代码和更多DllImport示例：http://msdn.microsoft.com/en-us/library/aa288468(v=vs.71).aspx|682875|entityMap|0|LINK|mutability|MUTABLE|url|http://msdn.microsoft.com/en-us/library/aa288468(v=vs.71).aspx^0|I|G|1F|P|2G|10|0|0|6|9|I|1Q|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@$9|V|A|W|B|C]|$9|X|A|Y|B|C]|$9|Z|A|10|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|11|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|12|8|@$9|13|A|14|B|C]]|D|@$9|15|A|16|1|17]]|E|$]]|$1|M|3|-4|5|6|7|18|8|@]|D|@]|E|$]]]|N|$O|$5|P|Q|R|E|$S|T]]]]

If all fails, simply put the DLL in the <code>windows\system32</code> folder . The compiler will find it.
Specify the DLL to load from with: <code>DllImport("user32.dll"...</code>, set <code>EntryPoint = "my_unmanaged_function"</code> to import your desired unmanaged function to your C# app: 

<pre><code> using System;
using System.Runtime.InteropServices;

class Example
{
 // Use DllImport to import the Win32 MessageBox function.

 [DllImport ("user32.dll", CharSet = CharSet.Auto)]
 public static extern int MessageBox 
 (IntPtr hWnd, String text, String caption, uint type);

 static void Main()
 {
 // Call the MessageBox function using platform invoke.
 MessageBox (new IntPtr(0), "Hello, World!", "Hello Dialog", 0); 
 }
}
</code></pre>

Source and even more <code>DllImport</code> examples : <a href="http://msdn.microsoft.com/en-us/library/aa288468(v=vs.71).aspx" rel="nofollow">http://msdn.microsoft.com/en-us/library/aa288468(v=vs.71).aspx</a>

blocks|key|682930|text|比Ran建议使用GetProcAddress更好的是，只需在调用任何DllImport函数之前调用LoadLibrary+(只有一个文件名，没有路径)，它们就会自动使用加载的模块。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|682931|我已经使用此方法在运行时选择是加载32位还是64位本机DLL，而不必修改一堆P/Invoke-d函数。将加载代码放在具有导入函数的类型的静态构造函数中，一切都会正常工作。|682932|entityMap^0|8|E|Y|9|1D|B|0|0^^$0|@$1|2|3|4|5|6|7|J|8|@$9|K|A|L|B|C]|$9|M|A|N|B|C]|$9|O|A|P|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|Q|8|@]|D|@]|E|$]]|$1|H|3|-4|5|6|7|R|8|@]|D|@]|E|$]]]|I|$]]

Even better than Ran's suggestion of using <code>GetProcAddress</code>, simply make the call to <code>LoadLibrary</code> before any calls to the <code>DllImport</code> functions (with only a filename without a path) and they'll use the loaded module automatically.

I've used this method to choose at runtime whether to load a 32-bit or 64-bit native DLL without having to modify a bunch of P/Invoke-d functions. Stick the loading code in a static constructor for the type that has the imported functions and it'll all work fine.

blocks|key|467038|text|如果您知道C%2B%2B库在运行时所在的目录，就会很简单。我可以在你的问题陈述中看到这一点。名为myDll.dll的程序集将出现在当前用户的临时文件夹内的myLibFolder目录中。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|467039|string+str+=+Path.GetTempPath()+%2B+"..\\myLibFolder\\myDLL.dll";+|code-block|syntax|javascript|467040|您可以使用常量字符串继续使用DllImport语句，如下所示：|467041|[DllImport("myDLL.dll",+CallingConvention+=+CallingConvention.Cdecl)]
public+static+extern+int+DLLFunction(int+Number1,+int+Number2);|467042|在C#代码中调用DLLFunction函数(存在于C%2B%2B库中)之前，添加以下代码行：|467043|string+assemblyProbeDirectory+=+Path.GetTempPath()+%2B+"..\\myLibFolder\\myDLL.dll";+
Directory.SetCurrentDirectory(assemblyProbeDirectory);|467044|这将指示.NET+CLR在您在运行时获得的目录路径中查找非托管C%2B%2B库。调用Directory.SetCurrentDirectory将应用程序的当前工作目录设置为指定的目录。如果您的路径存在于由assemblyProbeDirectory+myDLL.dll表示的路径中，那么它将被加载。然后，您可以通过p/invoke调用所需的函数。|467045|entityMap^0|18|9|21|B|0|0|E|9|0|0|8|B|0|0|12|T|2Q|M|3D|9|0^^$0|@$1|2|3|4|5|6|7|W|8|@$9|X|A|Y|B|C]|$9|Z|A|10|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|11|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|12|8|@$9|13|A|14|B|C]]|D|@]|E|$]]|$1|M|3|N|5|H|7|15|8|@]|D|@]|E|$I|J]]|$1|O|3|P|5|6|7|16|8|@$9|17|A|18|B|C]]|D|@]|E|$]]|$1|Q|3|R|5|H|7|19|8|@]|D|@]|E|$I|J]]|$1|S|3|T|5|6|7|1A|8|@$9|1B|A|1C|B|C]|$9|1D|A|1E|B|C]|$9|1F|A|1G|B|C]]|D|@]|E|$]]|$1|U|3|-4|5|6|7|1H|8|@]|D|@]|E|$]]]|V|$]]

It'll be simple if you know the directory where your C++ libraries will be present at runtime. I can see that this is the case in your problem statement. Your assembly named <code>myDll.dll</code> would be present inside <code>myLibFolder</code> directory inside temporary folder of the current user.
<pre><code>string str = Path.GetTempPath() + &quot;..\\myLibFolder\\myDLL.dll&quot;; 
</code></pre>
You can continue using the <code>DllImport</code> statement using a constant string as shown below:
<pre><code>[DllImport(&quot;myDLL.dll&quot;, CallingConvention = CallingConvention.Cdecl)]
public static extern int DLLFunction(int Number1, int Number2);
</code></pre>
Before you call the <code>DLLFunction</code> function (present in C++ library) in your C# code add following line of code:
<pre><code>string assemblyProbeDirectory = Path.GetTempPath() + &quot;..\\myLibFolder\\myDLL.dll&quot;; 
Directory.SetCurrentDirectory(assemblyProbeDirectory);
</code></pre>
This instructs the .NET CLR to look for the unmanaged C++ libraries at the directory path which you obtained at runtime. Call to <code>Directory.SetCurrentDirectory</code> sets the application's current working directory to the specified directory. If your <code>myDLL.dll</code> is present at path represented by <code>assemblyProbeDirectory</code> path then it will get loaded. Then you can call the desired function through p/invoke.

blocks|key|683031|text|在配置文件中设置dll路径|type|unstyled|depth|inlineStyleRanges|entityRanges|data|683032|<add+key="dllPath"+value="C:\Users\UserName\YourApp\myLibFolder\myDLL.dll"+/>|code-block|syntax|javascript|683033|在应用程序中调用dll之前，请执行以下操作|683034|string+dllPath=+ConfigurationManager.AppSettings["dllPath"];++++
+++string+appDirectory+=+Path.GetDirectoryName(dllPath);
+++Directory.SetCurrentDirectory(appDirectory);|683035|然后调用dll，您可以像下面这样使用|683036|+[DllImport("myDLL.dll",+CallingConvention+=+CallingConvention.Cdecl)]
public+static+extern+int+DLLFunction(int+Number1,+int+Number2);|683037|entityMap^0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|R|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|S|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|T|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|U|8|@]|9|@]|A|$]]|$1|M|3|N|5|D|7|V|8|@]|9|@]|A|$E|F]]|$1|O|3|-4|5|6|7|W|8|@]|9|@]|A|$]]]|P|$]]

set the dll path in the config file

<pre><code>&lt;add key="dllPath" value="C:\Users\UserName\YourApp\myLibFolder\myDLL.dll" /&gt;
</code></pre>

before calling the dll in you app, do the following

<pre><code>string dllPath= ConfigurationManager.AppSettings["dllPath"]; 
 string appDirectory = Path.GetDirectoryName(dllPath);
 Directory.SetCurrentDirectory(appDirectory);
</code></pre>

then call the dll and you can use like below

<pre><code> [DllImport("myDLL.dll", CallingConvention = CallingConvention.Cdecl)]
public static extern int DLLFunction(int Number1, int Number2);
</code></pre>

blocks|key|683111|text|由于Invoke+Core3.0-也可以与.NET+5和.NET+6一起使用-您可以使用NativeLibrary.Load(string)在运行时动态加载非托管DLL，您可以通过P/Invoke使用它。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|683112|有关更多详细信息，请参阅此处的答案：https://stackoverflow.com/a/69958827/211672|683113|entityMap|0|LINK|mutability|MUTABLE|url|https://docs.microsoft.com/en-us/dotnet/api/system.runtime.interopservices.nativelibrary.load?view=net-5.0#System_Runtime_InteropServices_NativeLibrary_Load_System_String_|1|https://stackoverflow.com/a/69958827/211672^0|18|Q|18|Q|0|0|I|17|1|0^^$0|@$1|2|3|4|5|6|7|R|8|@$9|S|A|T|B|C]]|D|@$9|U|A|V|1|W]]|E|$]]|$1|F|3|G|5|6|7|X|8|@]|D|@$9|Y|A|Z|1|10]]|E|$]]|$1|H|3|-4|5|6|7|11|8|@]|D|@]|E|$]]]|I|$J|$5|K|L|M|E|$N|O]]|P|$5|K|L|M|E|$N|Q]]]]

Since .NET Core 3.0 - also works with .NET 5 &amp; .NET 6 - you can use <a href="https://docs.microsoft.com/en-us/dotnet/api/system.runtime.interopservices.nativelibrary.load?view=net-5.0#System_Runtime_InteropServices_NativeLibrary_Load_System_String_" rel="nofollow noreferrer"><code>NativeLibrary.Load(string)</code></a> to dynamically load unmanaged DLLs at runtime, which you can use via P/Invoke.
See this answer here on SO for more details: <a href="https://stackoverflow.com/a/69958827/211672">https://stackoverflow.com/a/69958827/211672</a>

blocks|key|467156|text|//[?]+Method+Sample;
[System.Runtime.InteropServices.DllImport("ramdom_Kernel32.dll")]+//[!]+Error+Sample
public+dynamic+MethodWithDllImport(){
++
}

partial+static+Main(){
++try{
++++//[?]+Exception+Cannot+Be+Handled+over+the+Attribute;
++++//++++handle+where+it+is+called;
++++MethodWithDllImport();
++}+
++catch{
+++//[?]+use+overloaded\other+name+methods
++}
}|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|467157|unstyled|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|H|8|@]|9|@]|A|$]]]|F|$]]

<pre><code>//[?] Method Sample;
[System.Runtime.InteropServices.DllImport(&quot;ramdom_Kernel32.dll&quot;)] //[!] Error Sample
public dynamic MethodWithDllImport(){
 
}

partial static Main(){
 try{
 //[?] Exception Cannot Be Handled over the Attribute;
 // handle where it is called;
 MethodWithDllImport();
 } 
 catch{
 //[?] use overloaded\other name methods
 }
}
</code></pre>

In fact, I got a C++ (working) DLL that I want to import into my C# project to call it's functions.

It does work when I specify the full path to the DLL, like this :

<pre><code>string str = "C:\\Users\\userName\\AppData\\Local\\myLibFolder\\myDLL.dll";
[DllImport(str, CallingConvention = CallingConvention.Cdecl)]
public static extern int DLLFunction(int Number1, int Number2);
</code></pre>

The problem is that it's gonna be an installable project, so the user's folder will not be the same (ex : pierre, paul, jack, mum, dad, ...) depending computer/session where it'd be runned on.

So I'd like my code to be a little more generic, like this : 

<pre><code>/* 
goes right to the temp folder of the user 
 "C:\\Users\\userName\\AppData\\Local\\temp"
then go to parent folder
 "C:\\Users\\userName\\AppData\\Local"
and finally go to the DLL's folder
 "C:\\Users\\userName\\AppData\\Local\\temp\\myLibFolder"
*/

string str = Path.GetTempPath() + "..\\myLibFolder\\myDLL.dll"; 
[DllImport(str, CallingConvention = CallingConvention.Cdecl)]
public static extern int DLLFunction(int Number1, int Number2);
</code></pre>

The big deal is that "DllImport" desire a "const string" parameter for the DLL's directory.

So my question is ::
What could be done in this case ?

How can I specify a [DllImport] path at runtime?

编译器

实际上，我得到了一个C++ (工作) DLL，我想将它导入到我的C#项目中来调用它的函数。当我指定DLL的完整路径时，它确实起作用了，如下所示：string str = "C:\\Users\\userName\\AppData\\Local\\myLibFolder\\myDLL.dll";[DllImport(st...

问如何在运行时指定[DllImport]路径？
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问如何在运行时指定[DllImport]路径？
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