So I have a situation where I am using a SqlDataAdapter to insert rows into a table in a SQL Server 2014 database.
The source of the data is an Excel spreadsheet.
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I had the same issue, and the solution was quite simple, once you've seen it... I had my Database in Visual studio, and its property "Copy to Output Directory" was set to "Copy always", instead of "Do not copy". So everytime I was running my code, the database was erased!
Solution : - modify your connection string so it points directly to your database - Change your database property to "Do not copy"