Thanks @BrendanRice for your reply. Unfortunately the thread you linked to suffered from a different issue than mine. The solution for the thread you linked to was changing the Target .NET version from 4.7.1 to 4.7.2 My project is already targeting 4.7.2

How did you go about the upgrade, what steps did you do?

My old Umbraco 7.12 wasn't in visual studio...

So I created a blank 4.7.2 .NET site in Visual Studio and copied all of the files from my Umbraco 7.12 site into that blank project.

Then I ran nuget and installed 7.15.6

Try to run the site in debug and I get the above error.

Thanks @BrendanRice. I'll give that a shot.

Good luck, also take backups at stages in between each major release upgrade in case you find something broken.

I did as you suggested. New blank .NET 4.7.2 project. Install Umbraco 7.12 Copy in everything from my 7.12 site (except bin and umbraco folders)

I hit this error on the first debug...

Could not load all types from "umbraco.DataLayer, Version=1.0.6795.23037, Culture=neutral, PublicKeyToken=null" due to LoaderExceptions, skipping: . System.IO.FileLoadException: Could not load file or assembly 'MySql.Data, Version=6.9.9.0, Culture=neutral, PublicKeyToken=c5687fc88969c44d' or one of its dependencies. The located assembly's manifest definition does not match the assembly reference. (Exception from HRESULT: 0x80131040) . System.IO.FileLoadException: Could not load file or assembly 'MySql.Data, Version=6.9.9.0, Culture=neutral, PublicKeyToken=c5687fc88969c44d' or one of its dependencies. The located assembly's manifest definition does not match the assembly reference. (Exception from HRESULT: 0x80131040) . System.IO.FileLoadException: Could not load file or assembly 'MySql.Data, Version=6.9.9.0, Culture=neutral, PublicKeyToken=c5687fc88969c44d' or one of its dependencies. The located assembly's manifest definition does not match the assembly reference. (Exception from HRESULT: 0x80131040) . System.IO.FileLoadException: Could not load file or assembly 'MySql.Data, Version=6.9.9.0, Culture=neutral, PublicKeyToken=c5687fc88969c44d' or one of its dependencies. The located assembly's manifest definition does not match the assembly reference. (Exception from HRESULT: 0x80131040) . System.IO.FileLoadException: Could not load file or assembly 'MySql.Data, Version=6.9.9.0, Culture=neutral, PublicKeyToken=c5687fc88969c44d' or one of its dependencies. The located assembly's manifest definition does not match the assembly reference. (Exception from HRESULT: 0x80131040)

Any idea?

Thanks again @BrendanRice. I wondered about that when I copied it in. Boom. Ok. I've got 7.12 stood up. Time to stepwise upgrade. Thanks for your help Brendan!

Well no build errors in 7.12, When it runs it takes to me to the login page for Umbraco. But, when I login it takes me right back to the login page.

Here's the URL when I debug: http://localhost:54794/umbraco/AuthorizeUpgrade?redir=%2finstall%2f%3fredir%3dtrue%26url%3dhttp%253a%252f%252flocalhost%253a54794%252f#/AuthorizeUpgrade?redir=%2Finstall%2F%3Fredir%3Dtrue%26url%3Dhttp%253a%252f%252flocalhost%253a54794%252f

It's an infinite loop.

I've tried modifying the url to: http://localhost:54794/umbraco or http://localhost:54794/

But both redirect to the AuthorizeUpgrade url above.

Are you sure the connection string is correct?

hmm maybe it's the umbracoConfigurationStatus. What does it say in the web.config app setting for this key?

<add key="umbracoConfigurationStatus" value=""/>

The connection string looks good. I switched it from a database on a SQL server to a local SQLCE database.

<add name="umbracoDbDSN" connectionString="Data Source=|DataDirectory|\Umbraco.sdf;Flush Interval=1;" providerName="System.Data.SqlServerCe.4.0"/>

I tested changing it to

<add key="umbracoConfigurationStatus" value="7.12"/>

Same experience with the infinite loop on the login page.

The connectionstring was good the SQLCE was bad. I recreated it and i'm good to go now (I think). Thanks for all your help!!!

I did have that issue at first. But, I did forgot password and reset my password. So that's not my issue now.