TRDP and TRDX files are produced by the Standalone Report Designer tool, and only the Standalone Designer can load them for editing via GUI. In Visual Studio you can open TRDX files as pure XML.
If you are using SqlDataSource in the report, you can save the connection string by name - 2. Data connection options
. Then the reporting engine will get the connection by name from the application's config file via ConfigurationManager.
If you prefer to change the connection string at run-time, you can use the approach illustrated in Changing the connection string dynamically according to runtime data.
I hope this helps.
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