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Connection string updated on server when publishing

i'm trying to get my connection string values updated on production server during publish. I'm trying the following with no results:
<connectionStrings>
add name="DataConnect" connectionString="Server=Pepe;Database=Oyeti;Integrated Security=SSPI;" xdt:Transform="Replace" />
and also added the xdt:Locator, but i don't think it's the correct way:
<connectionStrings>
add name="DataConnect" connectionString="Server=Pepe;Database=Oyeti;Integrated Security=SSPI;" xdt:Transform="Replace" xdt:Locator="Match(name)" />
What i'm not seeing there?
thanks!

You can add the xdt:Transform="SetAttributes" xdt:Locator="Match(name) attributes to the connectionString tag in your transformation file (Web.Release.config) to transform the values in your primary config file (Web.config). As an alternative, you can also specify connection strings in your publish profile.
Although the default transform file contains an example that shows how
to update a connection string, in most cases you do not need to set up
connection string transformations, because you can specify connection
strings in the publish profile. You'll do that in the deploy to IIS
and deploy to production tutorials.
https://learn.microsoft.com/en-us/aspnet/web-forms/overview/deployment/visual-studio-web-deployment/web-config-transformations

Where to find the location of IIS manager connection strings

I was getting an error saying that one of my connection string in my application's web.config file was already defined.
I checked in the IIS settings and when I checked the connection string property it was there already with Entry Type : Inherited.
So I went up the chain and went all the way up to the root of the localhost and checked the connection strings there.
I found a bunch of connection strings there as well.. but they're also all with Entry Type Inherited..
I checked the web.config file inside the wwwroot folder but didn't find any connection strings defined in there..
Where could these connection strings be coming from?...

Configuration files in .NET are inherited in the following order:
systemroot\Microsoft .NET\Framework\versionNumber\CONFIG\Machine.config
systemroot\Microsoft .NET\Framework\versionNumber\CONFIG\Web.config (ASP.NET only)
(application directory)\Web.config
So the connection strings that show up as "inherited" are specified in either of the upper two files.
Reference: MSDN: ASP.NET Configuration File Hierarchy and Inheritance
If you don't want to alter the machine-wide configuration, you can <clear /> them from being inherited in your application's configuration as explained in What does <clear /> signify when specifying a connectionstring?:
<connectionStrings>
<clear />
<add name="LocalSqlServer" connectionString="..." />
</connectionStrings>

Find out which web.config(s) have been loaded

I'm encountering an error indicating that the web.config being loaded by this particular sub-project of my solution has a connectionstring that conflicts with an existing entry from an already-loaded web.config
(Exception message is: Additional information: The entry 'connStr' has already been added.)
Is there a way to easily find out the list of all web.configs loaded/being loaded, so that I can ascertain where to conflict is arising

There is only one web.config that will be loaded, however, it will inherit from your machine configuration. For IIS this is here:
%windir%\Microsoft.NET\Framework\framework_version\CONFIG\machine.config
And for IIS Express in one of these places:
%userprofile%\documents\iisexpress\config\applicationhost.config
%userprofile%\my documents\iisexpress\config\applicationhost.config
$(solutionDir)\.vs\config\applicationhost.config (only for Visual Studio 2015 and above)
So you can remove the duplicate from there, or add a remove entry in your web.config, for example:
<connectionStrings>
<remove name="MyConnection" />
<add name="MyConnection" connectionString="..." providerName="System.Data.SqlClient" />
</connectionStrings>

I've had this problem before, I added inheritInChildApplications="false" in my main web.config. This way I know that my sub web.config will not have any conflict.

Create a connection string / connect to a database in asp.net?

I am trying to publish a website to make it go live and need to connect to a database. Currently I am using:
<connectionStrings>
<add name="UniversityContext" connectionString="Data Source=(LocalDb)\MSSQLLocalDB;Initial Catalog=RoomAudit;Integrated Security=SSPI;AttachDBFilename=|DataDirectory|\RoomAuditSystem.mdf" providerName="System.Data.SqlClient" />-->
</connectionStrings>
in my web.config which obviously using my local machine.
I've looked online and on here and can't seem to find a clear cut tutorial. Here is the database details:
DATABASE SERVER
mysql4.gear.host
with my username and password with reading and writing permissions.
If someone could point me in the right direction I would appreciate it - I'm also using Entity Framework if that makes any difference?
EDIT:
This is my new connection string:
<add name="UniversityContext" connectionString="Server=mysql4.gear.host;Database=databasename;User Id=username; Password=password;" providerName="System.Data.SqlClient" />
However, when I publish the website I get a runtime error?
Runtime error:
Server Error in '/' Application.
Runtime Error
Description: An application error occurred on the server. The current custom error settings for this application prevent the details of the application error from being viewed remotely (for security reasons). It could, however, be viewed by browsers running on the local server machine.
Details: To enable the details of this specific error message to be viewable on remote machines, please create a tag within a "web.config" configuration file located in the root directory of the current web application. This tag should then have its "mode" attribute set to "Off".
<!-- Web.Config Configuration File -->
<configuration>
<system.web>
<customErrors mode="Off"/>
</system.web>
</configuration>
Notes: The current error page you are seeing can be replaced by a custom error page by modifying the "defaultRedirect" attribute of the application's configuration tag to point to a custom error page URL.
<!-- Web.Config Configuration File -->
<configuration>
<system.web>
<customErrors mode="RemoteOnly" defaultRedirect="mycustompage.htm"/>
</system.web>
</configuration>
Console error:
Failed to load resource: the server responded with a status of 500 (Internal Server Error)

IMO, best place for learning to write connection strings is here: https://www.connectionstrings.com/sql-server/

Try this
<add name="UniversityContext" connectionString="Data Source=mysql4.gear.host;Initial Catalog=databasename;User ID=username;Password=password" />

I suggest to create file with .udl extension and test configuration.
It could help you to find proper parameters.

ConnectionString for assemblies

I have a website with a connection string listed in its web.config. The connection string is altered by the Publish feature so that it can reference a development database until it is released, when it references a separate release database.
The website accesses the databases through some assemblies, though. They are Class Libraries so they can't be Published, at least as far as I can tell. I read that the web.config would override the app.config connectionstrings, but that doesn't seem to be happening.
Whenever I Publish the release site references the development database, unless I alter the assemblies app.config files to reference the release database.
I don't want to have to remember to do that every time. How do I handle this?

You've got two issues here:
1. How to remember to publish the correct settings each time you publish:
One way to deploy such settings is by using web.config transformations in Visual Studio. This is pretty easy to set up and means that you do not have to remember to update the settings each time you publish.
As well as debug and release environments, you can also create transforms for "UAT", "Staging", "Beta" or whatever other configs you might need.
You might find these articles useful: here, here and here.
For example, here is a transform for a Release environment:
<?xml version="1.0"?>
<configuration xmlns:xdt="http://schemas.microsoft.com/XML-Document-Transform">
<connectionStrings>
<add name="MyDB"
connectionString="Data Source=ReleaseSQLServer;Initial Catalog=MyReleaseDB;Integrated Security=True"
xdt:Transform="SetAttributes" xdt:Locator="Match(name)"/>
</connectionStrings>
<system.web>
<compilation xdt:Transform="RemoveAttributes(debug)" />
<customErrors defaultRedirect="GenericError.htm"
mode="RemoteOnly" xdt:Transform="Replace">
<error statusCode="500" redirect="InternalError.htm"/>
</customErrors>
</system.web>
</configuration>
Above, you will see that the transform for Release mode sets the attributes of the MyDB connection string (xdt:Transform="SetAttributes"), removes the debug attribute from the compilation section and replaces the customErrors section with a new version.
It's a simple, yet very powerful technique.
2. How to get your assemblies to pick up the settings in the web.config
If your libraries have been written in the usual way, they should be retrieving their connection strings by simply accessing the [Web]ConfigurationManager.ConnectionStrings property. Like #Bob Horn says, they should then pick up the settings from the host process's config file (in this case the web.config of your web app).
However, sometimes you might find that a library is getting its settings from a .Settings file in the project, in which case things get a little more complicated. You will need to copy the settings section of the app.config in to the web.config. (You can also do this using the transforms technology described above.)
If you have access to the source code of the other assemblies, find the part of the code that retrieves connection strings. If it's not accessing the ConfigurationManager class, then that might explain why it's not picking up the web.config file.