Since we have many ways to use Connection String in .NET 2.0, it is probably that we are using duplicate connection string in web.config.
<connectionStrings><addname="ConnectionString"connectionString="Server=(local);Database=NorthWind;"/></connectionStrings><appSettings><add key="ConnectionString" value="Server=(local);Database=NorthWind;"/></appSettings>
❌ Bad example - Using duplicate connection string in web.config