## Try any of the following ...

1. **Enable Just My Code** 
 Go to Tools > Options > Debugging > General 
 Check "Enable Just my Code" 
 [![Enable Just my Code][1]][1] 

2. **Cache Symbols Locally** 
 Go to Tools > Options > Debugging > Symbols
 Browse to local directory (make sure it's not on a network share)
 Click "Load All Symbols" or run the project to hydrate the cache

 [![Cache Symbols][2]][2] 
 
3. **Remove Remote Symbol Servers** 

 When you select a remote symbol server, Visual Studio gives you the [following warning][3]:

 > The performance of remote symbols stores can vary due to latency, bandwidth, or availability of servers. Debugging performance can be improved by selecting the option to load only specified modules when enabling this server

 After loading your symbol cache, deselect remote symbols servers

 Go to Tools > Options > Debugging > Symbols
 Deselect "Microsoft Symbol Servers" to prevent Visual Studio from remotely querying the Microsoft servers.
 [![Deselect Microsoft Symbol Servers][4]][4]



## Further Reading

### Stack Overflow

* [Visual Studio debugging/loading very slow][5]
* [Visual Studio Build Very Slow][6]
* [Slow startup with IIS Express][7]
* [Website takes a long time to start after solution build][8]

### MS Docs

* [Visual Studio debugger documentation][9]
* [Debug only user code with Just My Code][10]
* [Specify symbol (.pdb) and source files in the Visual Studio debugger][11]
* [Debugger Settings and Preparation][12]


 [1]: https://i.stack.imgur.com/XAERs.png
 [2]: https://i.stack.imgur.com/N2dWb.png
 [3]: https://i.stack.imgur.com/0jBwS.png
 [4]: https://i.stack.imgur.com/xZ1T2.png
 [5]: https://stackoverflow.com/q/12567984/1366033
 [6]: https://stackoverflow.com/q/12095718/1366033
 [7]: https://stackoverflow.com/q/23880900/1366033
 [8]: https://stackoverflow.com/q/5553057/1366033
 [9]: https://learn.microsoft.com/en-us/visualstudio/debugger/?view=vs-2019
 [10]: https://learn.microsoft.com/en-us/visualstudio/debugger/just-my-code
 [11]: https://learn.microsoft.com/en-us/visualstudio/debugger/specify-symbol-dot-pdb-and-source-files-in-the-visual-studio-debugger
 [12]: https://learn.microsoft.com/en-us/visualstudio/debugger/debugger-settings-and-preparation

I have an issue which is practically similar to https://stackoverflow.com/questions/12567984/visual-studio-debugging-loading-very-slow but I haven't managed to find a solution to such a problem.

I have tried all what is described within that question and still, the symbol loading for the very first time is drastically slow.

Similarly to the other question, when starting an MVC project, I get several lines within the Output panel which consist of something similar to:

    'iisexpress.exe' (Managed (v4.0.30319)): Loaded 'C:\Windows\Microsoft.NET\Framework\v4.0.30319\Temporary ASP.NET Files\root\02ba097f\ab73cbf7\App_Web__headerusermenu.cshtml.ee708ea.myhgafpb.dll', Symbols loaded.
    'iisexpress.exe' (Managed (v4.0.30319)): Loaded 'C:\Windows\Microsoft.NET\Framework\v4.0.30319\Temporary ASP.NET Files\root\02ba097f\ab73cbf7\App_Web__layoutcmsbase.cshtml.ce72eb6d.ovoanhe-.dll', Symbols loaded.
    'iisexpress.exe' (Managed (v4.0.30319)): Loaded 'C:\Windows\Microsoft.NET\Framework\v4.0.30319\Temporary ASP.NET Files\root\02ba097f\ab73cbf7\App_Web__notificationmessage.cshtml.5346933.9aei7ems.dll', Symbols loaded.

Such entries take around 300 - 500 ms each and these are executed for all the Partial Views we have within the project, which are quite considerable.

I have tried the solution within the other question but still didn't get any fast response times. 

These are some tests we have made:

Using IIS Express
-----------------
- Loading website initially takes roughly 2 minutes
- Stopping website and starting again takes around 1 min 45 sec
- Once the website is running, I press on Load All Symbols (Tools > Otions > Debugging > Symbols > Load all symbols) and then stop project and run again, and it takes much less, round 25 sec.  Still, the Load All Symbols button is disabled while the project isn't running, so for the very first time, I would need to wait until the project has loaded in order to press Load All Symbols

Using Visual Studio Development Server
--------------------------------------
- Starting initially, takes roughly 50 sec
- Stopped project and started again, takes roughly 20 sec
- Clicking on Load All Symbols, stopping project and starting again takes roughly 15 sec

This is getting extremely frustrating as it is taking an extremely long amount of time in order to load project for the first time.  

Any possible solution other than those mentioned within the question https://stackoverflow.com/questions/12567984/visual-studio-debugging-loading-very-slow which might help?

Visual Studio debugging painfully slow when loading symbols

All `web.config` files work off multiple *cascading levels of inheritance* at the machine, IIS, project, and folder level locations, with each providing a higher degree of specificity. 

If you're getting this error, it means you've either:

1. Added the same key twice in the same file (unlikely since you would've seen it)
2. The same key already exists in a separate file higher up the inheritance chain

There can be a lot of different root causes for #2, but if you want to side step them, you can just remove any previous declarations and then re-add your own at that level (I'd pay good money for an upsert feature).

So just add `<remove>` tags like this for any offending elements:



<pre><code>&lt;system.webServer&gt;
 &lt;modules runAllManagedModulesForAllRequests="true"&gt;

 &lt;remove name="ErrorLog" /&gt;
 &lt;remove name="ErrorMail" /&gt;
 &lt;remove name="ErrorFilter" /&gt;

 &lt;add name="ErrorLog" type="Elmah.ErrorLogModule, Elmah" preCondition="managedHandler" /&gt;
 &lt;add name="ErrorMail" type="Elmah.ErrorMailModule, Elmah" preCondition="managedHandler" /&gt;
 &lt;add name="ErrorFilter" type="Elmah.ErrorFilterModule, Elmah" preCondition="managedHandler" /&gt;

 &lt;/modules&gt;
&lt;/system.webServer&gt;
</code></pre>

In Visual studio, Solution->Web.Project->Properties->Web, I have changed my Project Url from     `http://localhost:51123/` to `http://localhost:51123/NewProjectName` and I keep getting this error:

"*Cannot add duplicate collection entry of type 'add' with unique key attribute 'name' set to ....*" on every module added. 

Adding a remove tag works but then it should have been a problem even before i changed the url. Any suggestions?

IIS express: Cannot add duplicate collection entry of type 'add' with unique key attribute 'name' set to

### Try any of the following fixes....

1. **Clean + Rebuild Solution**
2. **Restart Visual Studio**
3. **Run Visual Studio as Admin**
4. **Restart Computer**
5. **Launch Without Debugging**
 <kbd>Ctrl</kbd> + <kbd>F5</kbd>

6. **Step Into Debugging** 
 Hit <kbd>F11</kbd> to start debugging by stepping into the first line of executed code. If that works, the problem is likely in your code somewhere (possibly an *ehem* StackOverflow Exception)

 [![Step Into][1]][1]

 [![Breakpoint on Application_Start][2]][2] 


7. **Break on CLR Exceptions** 
 If there is a problem with the code on startup, you should break when thrown 
 Go to Debug > Windows > Exception Settings (<kbd>Ctrl</kbd> + <kbd>Alt</kbd> + <kbd>D</kbd>) 
 Select `Common Language Runtime Exceptions`

 [![Exception Settings][3]][3]

 [![Common Language Runtime Exceptions][4]][4] 


8. **Change Project Port** 
 Go to Project > Properties > Web > Project URL 
 Try using **`8080`**, but any change might work

 [![Web Settings > URL > Port][5]][5] 


9. **Create Virtual Directory** 
 In the above screenshot, select `Create Virtual Directory` to the right of the Project Url 

10. **Delete `.vs` folder** 
 Open the Directory where the solution / project lives. 
 Make sure *hidden* file are visible, and delete the `.vs` folder

 [![Delete .vs folder][6]][6] 


11. **Restart IIS Express** 
 In the system tray, right click on IIS Express and select Exit

 [![Exit IIS Express][7]][7] 


12. **Enable 64 Bit IIS Express** 
 ***If** you're on a 64 bit machine*... 
 Go to Tools > Options > Projects and Solutions > Web Projects 
 Select `Use the 64 bit version of IIS Express...` 
 

 [![Use the 64 bit version of IIS Express][8]][8] 

13. **Check Event Viewer** 
 Check for any additional diagnostic information in Event Viewer under Windows Logs > Application

 [![Event Viewer][9]][9]

 [![Windows Logs > Application > IIS Express][10]][10] 

14. **Run IIS Express from cmd line** 
 You can rule out if there's an issue with Visual Studio or your Web Project itself. 
 Here's the docs on [Running IIS Express from the Command Line][11] 
 Pass in the path to the root of your project (where the web.config) is located

 ```bash
 > "C:\Program Files (x86)\IIS Express\iisexpress.exe" /path:C:\repos\project\
 ```
 

15. **Download IIS Express** 
 Get the standalone installer for [Internet Information Services (IIS) 10.0 Express][12] and try again 

16. **Disable Edit and Continue** 
 Go to Project > Properties > Web > Debuggers 
 Deselect `Enable Edit and Continue` although this will remove that functionality

 [![Disable Edit and Continue][13]][13] 

### Further Reading: 

* [ASP.NET MVC5/IIS Express unable to debug - Code Not Running][14]
* [IIS Express crashes when starting a site from visual studio][15]
* [Unable to launch IIS Express Web server][16]


 [1]: https://i.stack.imgur.com/LDQJO.png
 [2]: https://i.stack.imgur.com/pdWja.png
 [3]: https://i.stack.imgur.com/KPs8R.png
 [4]: https://i.stack.imgur.com/cpjCc.png
 [5]: https://i.stack.imgur.com/F7LSt.png
 [6]: https://i.stack.imgur.com/0kMOn.png
 [7]: https://i.stack.imgur.com/V5Cg6.png
 [8]: https://i.stack.imgur.com/j6UG0.png
 [9]: https://i.stack.imgur.com/0sxyb.png
 [10]: https://i.stack.imgur.com/Opl08.png
 [11]: https://learn.microsoft.com/en-us/iis/extensions/using-iis-express/running-iis-express-from-the-command-line
 [12]: https://www.microsoft.com/en-us/download/details.aspx?id=48264
 [13]: https://i.stack.imgur.com/zIO4f.png
 [14]: https://stackoverflow.com/q/19472682/1366033
 [15]: https://stackoverflow.com/q/30406261/1366033
 [16]: https://stackoverflow.com/q/45480722/1366033

When running my solution in debug mode, IIS Express and Internet Explorer as the browser, I get the following error: 

```none
The program '[12604] iisexpress.exe: Program Trace' has exited with code 0 (0x0).
The program '[12604] iisexpress.exe' has exited with code 0 (0x0).
```

I'm using Visual Studio 2017.  If I change to Chrome, I do not get this. 

The only way to resolve this and still use IISExpress and IE is to go into my properties of the web project and uncheck **Enable Edit and Continue** under Debuggers.  

Any idea as to why? 