Category: Tips and tricks

Breakpoints cannot be hit when debugging C# in Visual Studio

When this happens, there can be a few reasons

-You attached to the wrong process.

-The build profile was changed to Release instead of Debug, thus no symbols are generated for debugging.

-You opened multiple instances of Visual Studio or programs that lock the PDB file, so when you make a new build the PDB file fails to be regenerated to match the new DLL.

-There are assemblies with classes with same name in the same namespace (for example DI may be configured to load different assemblies depending on some configuration). Visual Studio load the debug file for the wrong assembly when you are debugging some code. VS may assume that there is only one implementation of a a class in same namespace.

Steps to resolve

Make sure you attach to the correct process.

Make sure the build profile is Debug.

Clean and rebuild the solution.

If there are multiple assemblies with classes with the same name, try deleting the one that is not in use and then rebuild. Best option is to avoid classes with same name in same namespace. VS will be confused.

Last step, log out and log in again, or restart the computer to kill the processes that are locking the PDB. It could even be some Visual Studio bug.

Unit testing code using Entity Framework Core

https://docs.microsoft.com/en-us/ef/core/miscellaneous/testing/

I tried to use Moq to mock the DbContext and IQueryable<>, but it seems to be really complicated. It’s also not recommended by Microsoft.

For unit testing, it’s recommended to use a real database, perhaps using an in-memory database or a temporary sqlite database. Whatever the type of database you use, install the required NuGet package.

Create a self signed root CA certificate that works in Chrome in Ubuntu using openssl

This was really a lot of work as I’m not familiar with SSL and openssl. Took me a few days digging the net and trying many things to eventually make this work.

I was trying to make a Ubuntu client to trust a Windows webserver.

A few things I learned

  • If your certificate only have Common name, but your Subject Alternative Name is not in the cert, Chrome will complain with error ERR_COMMON_NAME_INVALID
    • Which is inaccurate and misleading.
    • Apparently, Common Name has been technically obsolete for 2 decades(!) and now the domain name must be put in SAN, which requires using openssl extension.
  • Using New-SelfSignedCertificateEx from Microsoft to generate the cert in Windows, the cert will not be trusted in Ubuntu, for some unknown reason. However if you install the cert in a Windows client and browse the website, it works.
  • For some application, you need to have a Friendly Name in the cert.

Steps to do it

Instructions are from the below link

https://www.ibm.com/support/knowledgecenter/SSZQDR/com.ibm.rba.doc/LD_rootkeyandcert.html

Generate the private key of the root CA:

openssl genrsa -out rootCAKey.pem 2048

Generate the self-signed root CA certificate, with SAN, you need openssl 1.1.1

openssl req -x509 -sha256 -new -nodes -key rootCAKey.pem -days 3650 -out rootCACert.crt -addext “subjectAltName = DNS:<Your domain name>”

Refer to this stackoverflow question on how to add SAN: https://security.stackexchange.com/questions/74345/provide-subjectaltname-to-openssl-directly-on-the-command-line

Create a pfx file to install in Windows web server.

openssl pkcs12 -export -out rootCACert.pfx -inkey rootCAKey.pem -in rootCACert.crt -name “<Your domain name>”

Afterwards, import the pfx file to the certificate store of the Windows Server using Microsoft Management Console and configure your webserver to use this certificate.

For Ubuntu Client, install to ca-certificates

sudo cp rootCACert.crt /usr/local/share/ca-certificates

sudo update-ca-certificates

Test using cURL, you may need to configure DNS or hosts file

curl https://<Your domain name>

Chrome and Firefox use their own certificate stores, so you need to add the certificates through their settings GUI. cURL will still work if cert doesn’t have SAN, but Chrome will complain as mentioned above.

Read single aggregate historical values from OPC UA

When reading processed historical data from OPC UA server, if you don’t set processing interval, only one value will be returned.

So if you use aggregation function Max from StartTime to EndTime, if you don’t specify the processing interval, it will return the maximum value from start time to end time.

If you specify the processing interval to 1 hour, it will return multiple max values for each hour within StartTime to EndTime.