An error occurs while loading my ASP.NET application after it is configured for IIS

Question

I changed my ASP.NET web application to use Local IIS, instead of IIS Express. Now after re-opening the solution, the following error occurs while loading the application:

error : Project 'Atlas2' could not be opened because the Visual C# 2015 compiler could not be created. 'Atlas2' is already part of the workspace.

error : Project 'Atlas2' could not be opened because the Visual C# 2015 compiler could not be created. An item with the same key has already been added.

Would someone please help me how I can reload the project? I'm using Visual Studio Team Services (was TFS Online), if it helps.

Are you opening solution in Visual studio with admin privileges? Run visual studio in admin mode and check if it works? — Pankaj Kapare, Apr 21 '16 at 17:59

Mohammad Mirmostafa · Accepted Answer · 2016-04-23T10:16:29.740

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I solved my problem. I unloaded the project and edited .csproj file. I did the following changes:

<UseIISExpress>false</UseIISExpress> to true
Remove <UseIIS>True</UseIIS>
Remove <IISUrl>http://localhost/MyWebApp</IISUrl>

Then I reloaded the project. It worked. Actually it rolled back to use IIS Express.

edited Apr 23 '16 at 10:16

answered Apr 23 '16 at 10:10

Mohammad Mirmostafa

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Making these changes were not enough for me. I also had to restart Visual Studio after making the changes. – René Sep 29 '16 at 08:43
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Another point to add: in my case, I re-downloaded the whole solution from source control. When editing the file, I noticed that the ports were set wrongly. In my case 30339 http://localhost:30339/ In IIS, the port was set to 3434. When I changed 30339 to 3434, I could load the project again. – Tybs May 15 '17 at 13:50

score 26 · Answer 2 · answered Jul 29 '16 at 09:57

26

The same problem occurred at my system and got solved by running The Visual Studio in administrator mode. The issue was IIS having the same host+port name as ASP.NET project and without administrator rights Visual Studio was not able add the website.

answered Jul 29 '16 at 09:57

Vishnu

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I tried solution above with no joy, reverted back and tried this solution and it worked first time. Thanks for this :) – IfElseTryCatch Sep 15 '16 at 09:16
This got me when Windows 10 reboots after security updates and re-opens every open program. Of course it does not open Visual Studio in administrator mode so I got the error. – John81 Oct 12 '16 at 13:39

score 6 · Answer 3 · answered Oct 12 '16 at 09:18

6

I had this error after switching from IIS Express to full IIS with Visual Studio 2015. I was able to load the project when I ran Visual Studio as Administrator.

answered Oct 12 '16 at 09:18

red_dorian

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Judy007 · Answer 4 · 2016-09-01T20:52:59.147

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I was getting a similar error in VS 2015.

"could not be opened because the visual c# 2015 compiler could not be created." "with the same key has already been added"

I was able to workaround the issue by opening the solution in Visual Studio 2013, Cleaning the solution, closing visual studio, then opening the same solution in Visual Studio 2015.

I also noticed that after doing this sequence of events, the csproj file of the project that was initially giving this error updated its ProjectExtensions element and set <UseIIS>False</UseIIS>

Image below of diff between csproj when error was occuring and after workaround.

Keep in mind that before I used this workaround, I tried to update that element manually and set to false, but that did not work.

edited Sep 01 '16 at 20:52

answered Sep 01 '16 at 20:47

Judy007

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I also noticed that I was able to workaround the same issue by ensuring that my local IIS server had a site that had binding to port 80. It appears that VS actually ensures that IIS serves a site when http://localhost is requested. – Judy007 Sep 15 '16 at 23:34
In addition to this, I had to delete the _projectName_.csproj.user file to make it actually take effect. – Synesthetic Symphony Oct 28 '16 at 14:45

score 4 · Answer 5 · answered Feb 25 '17 at 09:25

The problem is the app has been configured to use local IIS instead of Express and their coud be two issues for which you are unable to load the app.

Issue 1. You don't have IIS installed in your local system, In this case you have to install IIS or have to open the .csproj file and do the changes:

  <UseIISExpress>false</UseIISExpress> to true
  Remove <UseIIS>True</UseIIS>
  Remove <IISUrl>http://localhost</IISUrl>

Issue 2. Visual studio doesn't have access to IIS, in this case just open the Visual studio in administrator mode.

score 4 · Answer 6 · answered Mar 14 '18 at 09:27

I was facing similar issue but none of the mentioned solutions worked for me.

However, I was opening my solution from within visual studio recent solutions list. But when I opened the solution file from explorer by double clicking on it, the project loaded correctly.

score 2 · Answer 7 · answered Apr 21 '16 at 18:25

This often happens when authentication has not been setup in IIS or the website (or virtual directory) has not been setup in IIS. To fix this problem, open IIS manager.

Make sure a website or virtual directory exists for the project and points to the folder that contains the bin folder for your project.
Open Authentication and enable Anonymous Authentication.
Click Edit while Anonymous Authentication is selected.
Select Specific user, enter your Windows credentials (domain\username).
Open .NET Authorization Rules.
Make sure only Allow/All Users exists.
Go to Application Pools->Advanced Settings.
Select Identity and enter your Windows credentials (domain\username).

This should open up the website so Visual Studio can load your project. If not, go to Advanced Settings for you site and select Physical Path Credentials. Make sure that's set to pass-through authentication.

Thanks for your answer. – Mohammad Mirmostafa Apr 23 '16 at 10:09 — Mohammad Mirmostafa, Apr 23 '16 at 10:09

score 0 · Answer 8 · answered Aug 19 '16 at 21:11

I was getting this error.

I am using IIS-Express. And I have VS2015.

After messing around with the .csproj file....I was able to get it to work.

After comparing my current file to what was in TFS source control, the only difference was this line.

Previously, this line did not exist. In my "working" (after messin' with it) file, I had

<UseGlobalApplicationHostFile />

Again, in the csproj that causes the error, I didn't have the magic line, but in the working csproj, I had it.

Below is the above line, in context. Only use the below for breadcrumbs, do not copy/paste all of it. The magic line is 3 from the bottom.

<?xml version="1.0" encoding="utf-8"?>
<Project ToolsVersion="4.0" DefaultTargets="Build" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
  <Import Project="$(MSBuildExtensionsPath)\$(MSBuildToolsVersion)\Microsoft.Common.props" Condition="Exists('$(MSBuildExtensionsPath)\$(MSBuildToolsVersion)\Microsoft.Common.props')" />
  <PropertyGroup>
    <Configuration Condition=" '$(Configuration)' == '' ">Debug</Configuration>
    <Platform Condition=" '$(Platform)' == '' ">AnyCPU</Platform>
    <ProductVersion>
    </ProductVersion>
    <SchemaVersion>2.0</SchemaVersion>
    <ProjectGuid>{xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx}</ProjectGuid>
    <ProjectTypeGuids>{E3E379DF-F4C6-4180-9B81-6769533ABE47};{349c5851-65df-11da-9384-00065b846f21};{fae04ec0-301f-11d3-bf4b-00c04f79efbc}</ProjectTypeGuids>
    <OutputType>Library</OutputType>
    <AppDesignerFolder>Properties</AppDesignerFolder>
    <RootNamespace>MyRootNamespace</RootNamespace>
    <AssemblyName>MyAssemblyName</AssemblyName>
    <TargetFrameworkVersion>v4.5</TargetFrameworkVersion>
    <MvcBuildViews>false</MvcBuildViews>
    <UseIISExpress>true</UseIISExpress>
    <IISExpressSSLPort />
    <IISExpressAnonymousAuthentication>enabled</IISExpressAnonymousAuthentication>
    <IISExpressWindowsAuthentication>enabled</IISExpressWindowsAuthentication>
    <IISExpressUseClassicPipelineMode>false</IISExpressUseClassicPipelineMode>
    <SccProjectName>SAK</SccProjectName>
    <SccLocalPath>SAK</SccLocalPath>
    <SccAuxPath>SAK</SccAuxPath>
    <SccProvider>SAK</SccProvider>
    <UseGlobalApplicationHostFile />
  </PropertyGroup>
  <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Debug|AnyCPU' ">

Maryam · Answer 9 · 2016-12-07T09:39:46.427

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I had the same problem when I moved my WCF REST service from IISExpress to localhost. So, what I did was I opened the .csproj file in Notepad and looked for UseIISExpress, changed its value from false to True. Then opened VS2015 as administrator and it worked. The good thing is that when I run the project it is still running on my localhost not IISExpress.

edited Dec 07 '16 at 09:39

answered Dec 07 '16 at 09:25

Maryam

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Jawid · Answer 10 · 2018-04-23T11:54:31.117

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I had this issue with an upgrade for Visual Studio 2017. It has been fixed and is now available in an updated release.

You can download the latest update via the in-product notification or from https://www.visualstudio.com

Ref: Project could not be opened because the Visual C# 2017 compiler could not be created

edited Apr 23 '18 at 11:54

answered Apr 23 '18 at 09:19

Jawid

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score 0 · Answer 11 · answered Apr 30 '18 at 04:50

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I created a new Sln file.

Close the Solution.

Open the Project file of the main project. Add the offending projects back to the new Sln file.

Save the Sln file over the top of the old faulty one.

answered Apr 30 '18 at 04:50

Jeremy Thompson

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score -1 · Answer 12 · answered Nov 21 '17 at 20:15

I had the same exact error, this is what solved my issue. In the root of your solution you should see a .vs/config/applicationhost.config. In this folder delete the offending site. Mine looked like this:

        <site name="FrontEnd.Web" id="2">
            <application path="/" applicationPool="Clr4IntegratedAppPool">
                <virtualDirectory path="/" physicalPath="C:\xxxxx\xxxxx\xxxxx\FrontEnd.Web" />
            </application>
            <bindings>
                <binding protocol="http" bindingInformation="*:3391:localhost" />
            </bindings>
        </site>

I deleted the entire site tag for this application, saved and then, right-clicked my solution > Add > Existing Project and re-added the project to the solution.

An error occurs while loading my ASP.NET application after it is configured for IIS

12 Answers12