Connection strings in Entity Framework

Question

I am referencing 2 databases in ASP.NET using Entity Framework.

In my web.config file, I can see the connection strings for the 2 databases:

<connectionStrings>
    <add name="RContext" 
         connectionString="metadata=res://*/Models.RModel.csdl|res://*/Models.RModel.ssdl|res://*/Models.RModel.msl;provider=System.Data.SqlClient;provider connection string=&quot;data source=localhost\SQLEXPRESS;initial catalog=RStreamline;integrated security=True;MultipleActiveResultSets=True;App=EntityFramework&quot;" 
         providerName="System.Data.EntityClient" />
    <add name="CEntities" 
         connectionString="metadata=res://*/Models.CModel.csdl|res://*/Models.CModel.ssdl|res://*/Models.CModel.msl;provider=System.Data.SqlClient;provider connection string=&quot;data source=localhost\SQLEXPRESS;initial catalog=RStreamline;integrated security=True;MultipleActiveResultSets=True;App=EntityFramework&quot;" 
         providerName="System.Data.EntityClient" />
</connectionStrings>

Can I somehow implement alternate connection strings where the datasource refers to the prod server for the release?

I'll counter that question with another: how are planning to deploy the site? You could just a publish profile: learn.microsoft.com/en-us/aspnet/core/host-and-deploy/… — Andrew Corrigan
– Andrew Corrigan, Commented Apr 29, 2022 at 14:31
Connection strings don't reference tables. Both of those connection strings reference the same server and database, you may not need both. Anyway, there are multiple ways to transform configuration files or pull in configuration. As mentioned it helps to know what deployment mechanism you are using. Maybe start here — Crowcoder
– Crowcoder, Commented Apr 29, 2022 at 14:39
I'm deploying by publishing to a folder, then copying to the target server. So @AndrewCorrigan, I've checked the link and it seems that I can create 2 profiles, and use the appropriate connection string in each for the SQL dependency? Would I then use ConfigurationManager to grab the string? — user3825344
– user3825344, Commented Apr 29, 2022 at 15:28
I also checked the link from @Crowcoder and I could equally use the Web.Release.config to transform the string? I would like to use only one connection string, not sure yet how to get rid of the second one but I'm looking into it. — user3825344
– user3825344, Commented Apr 29, 2022 at 15:31

Nate · Accepted Answer · 2022-04-29 15:25:14Z

1

This is typically handled with web.config transforms.

In your project you would have:

web.config
web.Release.config

For example in your web.Release.config transform you would have something like this:

<?xml version="1.0"?>
<configuration xmlns:xdt="https://schemas.microsoft.com/XML-Document-Transform">
  <connectionStrings>
    <add name="RContext" 
      connectionString="RContext-Prod-Connection-String" 
      xdt:Transform="SetAttributes" xdt:Locator="Match(name)"/>
    <add name="CEntities" 
      connectionString="CEntities-Prod-Connection-String" 
      xdt:Transform="SetAttributes" xdt:Locator="Match(name)"/>
  </connectionStrings>
</configuration>

You'll notice the xdt:Transform="SetAttributes" xdt:Locator="Match(name)" bit, which says, in the main web.config find the connectionString by name and replace its attributes with the ones defined here.

This will automatically happen when you publish the application.

answered Apr 29, 2022 at 15:25

Nate

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2 Comments

user3825344 Over a year ago

I've seen examples of connection strings, like your example @Nate, that look to me like actual connection strings. So you are saying that it works just as well for the weird looking connection strings used by Entity Framework as in my original post?

user3825344 Over a year ago

So I've found that EF connection strings can be copied into the web.release.config, as well as the more normal looking (!) SQL connection strings. Thanks all! For other newbies like myself, the connections strings don't need to be built into the application as such. If the connections in the web.config don't work, just change them, restart the website and try again, and your changes get picked up at runtime, provided you used the Configuration Manager to pick them up in your code e.g. string connString = ConfigurationManager.ConnectionStrings["MainConnectString"].ConnectionString;. Wild.

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