Connection strings in Entity Framework

Friday, April 29, 2022 by Nate Bross

Someone asked on Stack Overflow:

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 posted the following answer, which was chosen as the accepted answer and received 1 upvote:

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.

Originally posted on Stack Overflow — 1 upvotes (accepted answer). Licensed under CC BY-SA.