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Fixing error “..an attempt was made to load a program with an incorrect format.”

Tuesday, April 14th, 2015

For a few hours I had been struggling with this error message when I tried to launch a WCF service (MyProductService.svc) from IIS7 hosted site:

Could not load file or assembly 'SomeExistingDotNetAssembly' or one of its dependencies. An attempt was made to load a program with an incorrect format.

The assembly was not built on my 64-bit machine initially so I suspected there must be something to do with that. After many failed internet searches, I decided to search for the detail error message below:

System.Web.Configuration.CompilationSection.LoadAssemblyHelper(String assemblyName, Boolean starDirective) +12857578
   System.Web.Configuration.CompilationSection.LoadAllAssembliesFromAppDomainBinDirectory() +503
   System.Web.Configuration.AssemblyInfo.get_AssemblyInternal() +142
   System.Web.Compilation.BuildManager.GetReferencedAssemblies(CompilationSection compConfig) +334
   System.Web.Compilation.BuildManager.CallPreStartInitMethods(String preStartInitListPath, Boolean& isRefAssemblyLoaded) +148
   System.Web.Compilation.BuildManager.ExecutePreAppStart() +172
   System.Web.Hosting.HostingEnvironment.Initialize(ApplicationManager appManager, IApplicationHost appHost, IConfigMapPathFactory configMapPathFactory, HostingEnvironmentParameters hostingParameters, PolicyLevel policyLevel, Exception appDomainCreationException) +1151


And that finally got me to a post from Stackoverflow which had these sacred words in it:

 Bad Image Format Exception usually means you tried to load a x64 Assembly / native DLL into an 32Bit process or vice versa a 32Bit Assembly into an x64 Process.

I felt I was close to hitting the jackpot! Then another user’s comment on IIS Application Pool setting settled the win for me:

 ...go into your IIS 7 manager console, find the application pool your app is running in, right-click on it, go to Advanced Settings, and change the Enable 32-bit Applications setting to true

And that was all it take to clear my error; after that change on the Application Pool, I clicked my “MyProductService.svc” again and now it rendered the wsdl xml nice and clean.

I am so grateful to these folks who shared and spent time to answer questions. So I reminded myself to do the same whenever I could.

NT AUTHORITY\NETWORK SERVICE does not have write access to ‘..\Temporary ASP.NET Files’.

Wednesday, January 4th, 2012

Got this error while trying to browse to a WCF service from IIS7: The current identity (NT AUTHORITY\NETWORK SERVICE) does not have write access to ‘D:\WINDOWS\Microsoft.NET\Framework\v4.0.3019\Temporary ASP.NET Files’. 

What happened? There must be some recent Windows updates to IIS7 that had messed up the previously security settings, but this was just my guessing. Important thing was how to fix this quickly. Found a post here granting access to IIS configuration and other directorys used by ASP.Net, and executed this line of command:

C:\Windows\Microsoft.NET\Framework\v4.0.30319>aspnet_regiis -ga “NT Authority\Ne
twork Service”

And that took care of it. “Network Service” is the identity used by the Application Pool used by the WCF service.

Allow other machine to connect to WCF Service hosted on localhost, Win7/IIS7

Thursday, November 10th, 2011

Moving along with my WCF project; today I needed to connect to the WCF services developed and published to my development machine (localhost, let’s mask its name as “dev1″) from another machine, named “user1″,  in the same network domain, and got the “Operation timed out” error 118. My localhost machine is a Windows 7 Enterprise and the WCF services are hosted on IIS7. Obviously, this was a security setting on the firewall on local machine that had blocked remote access.  Below are the steps I went through to get the problem resolved:

  1. First, I checked if I had access to default port, 80 at dev1 from user1 before I did anything; I browsed to http://dev1/Defaultsite/Default.aspx, and fair enough, not a chance – page was not rendering.
  2. On localhost (dev1), I went to Control Panel -> System and Security -> Windows Firewall -> Allowed Programs; highlighted “World Wide Web Services (HTTP) and changed settings -> checked “Domain” and “Home/Work (private)” checkboxes.
  3. Now browsed to http://dev1/Defaultsite/Default.aspx again and it worked!
  4. But when I browsed to a different port at dev1, http://dev1:8088/WcfHost/Service1.svc, I got denied again, error 118, “The operation timed out”, scary..I thought that I might need to turn on Windows Communication Foundation allowed programs inside Windows Firewall; so I did that but then it sill not worked.
  5. Is this WCF issue or port opening issue? To test that, I created a plain website, TestWeb, and hosted at http://dev1:8088/Testweb, and it still cannot be accessed from “user1″ machine. So this must be that port 8088 is not accessible from another machine.
  6. Back to Windows firewall config tool and went to Advanced Security Settings and created a new inbound connection rule, “RemoteAccessToPort8088″ to allow remote connection to port 8088 and 444.
  7. And this did it! Now I was able to access both http://dev1:8088/WcfHost/Service1.svc and https://dev1:444/WcfHost/Service1.svc from “user1″ machine.

Run .Net 1.1 Web Project in Windows 7/IIS7

Tuesday, November 1st, 2011

I have to develop and support three versions of .Net projects on one Windows 7 machine running IIS7. After installing VS2003, VS2008 and VS2010 on the machine, it was not without some struggling to get the legacy .Net 1.1 project to run seamlessly in IIS7, so it is worthwhile to write down a few key steps here:

  1. Created a .Net 1.1 website, called Net1_1 in IIS7 and selected Application pool ASP.Net 1.1 from the available Application pool drop-down. The ASP.Net 1.1 application pool was created automatically when Framework 1.1 was installed. If this application pool is not present, that is an indication that .Net 1.1 framework has not been installed or was not installed properly.
  2. Made sure that the ASP.Net 1.1 app pool “Managed Pipeline Mode” is “Classic”, which is default, instead of “Integrated”.
  3. At this point, I tried to browse to the .Net 1.1 app directly from IIS7, I got all sort of errors. They were caused by that ISAPI filter for .Net 1.1 was not  present by default in IIS7. To fix that, I selected the Net1_1 site -> Features View and double-clicked on “ISAPI Filters” icon; clicked on Add, gave it a name “Asp.Net 1.1″ and set “Executable” to be “C:\Windows\Microsoft.NET\Framework\v1.1.4322\aspnet_filter.dll”.
  4. Lifted the ISAPI and CGI restriction on the filter by going in to ISAPI and CGI Restrictions pane (accessed from Machine level Feature View) and changed Restriction from “Not Allowed” to “Allowed”.
  5. Almost done; I still got “Access denied” error after all these, why? Googled for “running .net 1.1 on IIS7″ and found a useful post at http://blogs.iis.net/rakkimk/archive/2008/03/20/iis7-running-asp-net-1-1-applications.aspx, which pointed me to download and install .Net framework 1.1 service pack 1. After that, I was able to bring the .Net 1.1 site back to live in IIS7!
  6. Another error, “Error while trying to run project: Unable to start debugging on the web server. Access is denied.”, arose when I tried to debug the .Net 1.1 project from VS2003. What’s going on? Well, it’s the notorious Windows 7 “Run as Administrator” thing! I had to run VS 2003 as administrator, open the project from VS2003, and then the error went away. What an inconvenience!

Use makecert.exe to generate certificates for WCF service in Windows 7/IIS7

Tuesday, September 27th, 2011

-   In order for server certificate to be found by WCF wsHttpBinding’s serviceCertificate, the certificate must be stored in LocalMachine

Notes below describe the process of creating a self-signed certificate, storing in Localmachine, import it to Trusted Root CA, and then use it to sign other certificates to be used for server and client

Generate a self-signed Certificate and Root Trust it


  1. Launch Vs2010 Command Prompt:
    Start -> All Programs -> Visual Studio 2010 -> Visual Studio Tools -> Visual Studio Command Prompt (right click and Run as Administrator)
  2. Create a self-signed (-r), private key exportable (-pe), saving to personal folder (-ss my) under local machine (Local Computer, sr localmachine), named (-n) “YangsoftCA”,common name (-in) “Yangsoft.com”  with private key file (-sv) as “YangsoftCA.pvk” and public key file “YangsoftCA.cer”Command:

    C:\Windows\system32>makecert -r -pe -ss my -sr LocalMachine -n “CN=YangsoftCA”  -sv  “YangsoftCA.pvk” YangsoftCA.cer

    Password was prompted to secure the private key file

  3.  Open certificate.msc, and this certificate “YangsoftCA” appear under Local Computer / Personal store:

    Certificates under Certmngr.msc

    Figure 1 Certificate created by makecert.exe appears under Local Computer/Personal folder

  4. We intended to use this certificate as root level certificate authority so it can be used to issue chain trusted certificates for encrypting communications between server and client, as well as authenticating web clients that are going to access the WCF service hosted on the server. At this point, when I double clicked on the certificate and opened up the property window, it said that the certificate authority was not trusted, as shown in Figure 2:

    Certificate not root trusted

    Figure 2 MMC - certificate not yet trusted

  5. To make this certificate the root of the trust chain, imported the YangsoftCA.cer file into the Trusted Root Certificate Authorities store (right-clicked on the certificate, copied and then pasted into Trusted Root Certificate Authorities) ; once I did that, now when I went back to the personal store and opened the “YangsoftCA” certificate, the status changed to “OK”, as shown in Figure 3.

    Certificate root trusted

    Figure 3 Certificate imported to Root Trusted CA

  6. Now, I can use it to issue other certificates down the trust chain.

Use the Root Trusted Certificate to Issue Chain Trusted Certificates

First, used the YangsoftCA to sign a certificate to be used on server-side; as it is to be used for the server where WCF service is to be hosted, the signed-certificate needed to be saved into local computer:


C:\Windows\system32>makecert -n “CN=SignedByYangsoftCA” -iv “YangsoftCA.pvk” -ic “YangsoftCA.cer” -pe -ss my -sr localmachine -sv “SignedByYangsoftCA.pvk” SignedByYangsoftCA.cer

Explanation of switches:

  1. The order of switches does not matter
  2. –iv and -ic: we used the private and public key files of the Root Trusted CA, “YangsoftCA” to sign this certificate
  3. –pe: make this new certificate’ private key exportable, which is saved to the file specified in –sv, “SignedByYangsoftCA.pvk”
  4. –sv: private key file of this certificate
  5. –ss: store name my=Personal
  6. –sr: store location, if not specified, it will go to “Current User” which we do not want in this case.
  7. Certificate file (or public key file): SignedByYangsoftCA.cer
  8. When this command was run, there were several prompts to enter password. First prompt was for Subject’s password (that is to protect file “SignedbyYangsoftCA.pvk”), the last prompt was for “Issuer”, which was needed to use the Issuer’s private key file, in this case, the “YangsoftCA.pvk”.

Where did it end up?

Opened the Certificates MMC, under Local Computer/Personal store, now we see “SignedByYangsoftCA”. Double click it and we can see the certificate shows as the sub level certificate under the certification path, as shown in Figure 4:

Certificate signed by Root Trusted CA

Figure 4 Certificate signed by root trusted certificate (YangsoftCA)

Assign the Certificate Signed by Root CA to Website

Now, let’s assign this certificate to the website that hosts the WCF service. There are two ways to do this. First, we can assign the server-side certificate via system.serviceModelsection in the web.config of WCF Service application, as shown in text box below:



<behavior name=”SvcBehavior”>

<serviceMetadata  httpsGetEnabled=”true” httpGetEnabled=”false”/>



<serviceCertificate findValue=”SignedByYangsoftCA” storeLocation=”LocalMachine” storeName=”My” x509FindType=”FindBySubjectName”/>


<authentication certificateValidationMode=”PeerOrChainTrust”  />



<!–this line turned on logging server error that is not thrown to EventLog. Use EventVwr/Application to find more details of the behind scene error; but make sure to turn this off after debugging is done since it will impact performance–>

<serviceSecurityAudit auditLogLocation=”Application” serviceAuthorizationAuditLevel=”Failure” messageAuthenticationAuditLevel=”Failure” suppressAuditFailure=”true” />





We can also install the SignedByYangsoftCA certificate to IIS and assign to the website through IIS7. In order for the certificate to be imported to IIS7, we first need to merge the private and public key files of the certificate into a single .pfx file that IIS7 is willing to receive.

Return to c:\windows\system32  and type these commands:

pvk2pfx  -pvk SignedByYangsoftCA.pvk –spc SignedByYangsoftCA.cer –pfx SignedByYangsoftCA.pfx

This merged the .pvk and .cer files into an exchangeable pfx file that can be imported to IIS7.

Install Certificate “SignedByYangsoftCA” to IIS localmachine.

  1. Start IIS7 -> Click on root folder Localhost node
  2. Double-click on Server Certificates then select “Import” from the “Action” pane to the right.
  3. Browse to c:\windows\System32\SignedByYangsoftCA.pfx; there is a place to enter password, but ignore it as this is not the password used to protect the private key file. Imported successfully.
  4. Now, go to the website where I want to assign the server certificate, click on Bindings, highlight the binding and click on Edit
  5. You can see now the “SignedByYangsoftCA” certificate is showing in the certificates dropdown list; select it and done, Figure 5.

    Bind Certificate to website, IIS7

    Figure 5 Binding certificate to website, IIS7

Now that the certificate is assigned, you can remove theentry from the web.config file of the WCF service app and the service should still render to https without problem.

Client Certificate

  1. Configure IIS7 to require client to have a certificate to access the WCF service:
    1. Open IIS7 and drill down to the virtual folder where the WCF service is published, in this case, “Demo” directory
    2. Double click on SSL Settings (on Feature View)
    3. Check the “Require Client Certificate” and Apply.

    Before a client certificate was issued, I tried to browse to the .svc file and the browser returned this message, as shown in Figure 6:

    Client certificate error

    Figure 6 If IIS7 Require Client Certificate is checked, this is client side error

  2. Now, let’s use the YangsoftCA that is already in the Root Trusted CA to issue a client certificate and then export as PFX file.Command:C:\Windows\system32>makecert -n “CN=ClientByYangsoftCA” -ss my -pe -sv “ClientBy
    YangsoftCA.pvk” -iv “YangsoftCA.pvk” -ic “YangsoftCA.cer” ClientByYangsoftCA.cer
    Explanation: generated a certificate signed (issued) by root trusted CA, “YangsoftCA”, named “ClientByYangsoftCA”, saved to CurrentUser/Personal Store, and exported private key file “ClientByYangsoftCA.pvk”.
  3. Then merged the private key and public key files into one PFX file:C:\Windows\system32>pvk2pfx -pvk ClientByYangsoftCA.pvk -spc ClientByYangsoftCA.
    cer -pfx ClientByYangsoftCA.pfx
  4. Browsed the ClientByYangsoftCA.pfx file and double clicked it, Certificate Import wizard popped up; followed the screen instruction, but ignore the password. I thought this password was the password used in protecting the private key file but when I entered it, it rejected; then I entered no password, and it took it. Is this a bug of what?

Create and apply a self-signed certificate – Windows 7/IIS7

Sunday, August 7th, 2011

Creating a self-signed certificate on Windows 7/IIS7 was quite a different experience and it took me more time to set it up and work correctly (in retrospect, it should have been easier as most of things can be configured with GUI tool). Anyway, I don’t want to repeat the pain and relearn how this is done, let me summarize the steps here to share with others and to help me find it easier in a rainy day:

  1. Open IIS7 (If IIS7 is not available from Administrative tools, go to Control Panel – > Programs – > Turn Windows Features On or Off.
  2. Click on machine node then double click on “Server Certificates” on the IIS pane
  3. Select “Create self-signed certificate” from the “Action” pane and give a friendly name such as “WcfSecure” in this case.
  4. Once the server certificate is created, view the certificate detail and write down the Thumbprint, something like ae 8f b2 b4 b0 b6 07 16 8e 73 51 35 38 cd 6b bb 7e 1f 12 d5, and remove the spaces to become ae8fb2b4b0b607168e73513538cd6bbb7e1f12d5, copy it to notepad for later use.
  5. Next, configured the Certificate to port, using VS2010 Guid tool to generate a GUID and run VS2010 Command prompt (must run as admin):netsh http add sslcert ipport= certhash=ae8fb2b4b0b607168e73513538cd6bbb7e1f12d5 appid={0270078A-39C3-47E8-845C-07D904672C71}
  6. Created a website to use the certificate so that WCF Service can be hosted in https mode; to do that click on Sites node and right click ->Add Web Site ->Named it “WcfDemo” and assign to Port 444 (443 and 442 have already been taken)
  7. Assign the certificate to the new website by choosing Binding type “https”, and pick the certificate from the Certificate drop down; certificate is on machine or server level, so there could be multiple certificates and multiple site can use same certificate.
  8. Refer to MSDN article at http://msdn.microsoft.com/library/ff406125.aspx for more in-depth detail.

It is important to note, that In IIS7, whenever a new website is created, it automatically creates a new application pool named the same as website, in this case, WcfDemo is the new app pool. And it automatically defaulted to use .Net Framework version 2.0, so be careful to manaully change it to the version that your Wcf app is using, in my case, changed to .net 4.0. Pay attention to Identity; by default, the Identity uses ApplicationPoolIdentity, other options are LocalService, LocalSystem, NetworkService, these are under Built-in account dropdown; you can also use Custom account and use the Windows user account for the application pool identity. If sqlexpress database is used for storing Membership users and if the security mode is set to use Integrated Security=true, then the
Application pool identity must use Localsystem or an “An unsecured or incorrectly secured fault was received from the other party. See the inner FaultException for the fault code and detail.” error will throw when WCF client calls the Wcf Service from this website.

If, however, the sql database uses “SQL Server Authentication” mode and passes in a predefined username and password in the sql connection string, then you can leave the default ApplicationPoolIdentity alone.