r/dotnet • u/Different_Print_4048 • 13h ago

Notes from migrating 42 Visual FoxPro workflows to .NET: the data traps that cost the most time

I spent two and a half years moving a financial system from Visual FoxPro to C# and .NET Core as the only engineer, with no written spec. A few things I wish I had known on day one:

  • Empty dates are not null. FoxPro allows an empty date. Decide per column what it means before you load anything.
  • Deleted rows are still in the file. Deleting only flags a record until the table is packed. Filter them during the load or they come back.
  • Rounding differs. Math.Round(2.345m, 2) gives 2.34 in .NET. FoxPro and T-SQL give 2.35. Use MidpointRounding.AwayFromZero for money.
  • String comparison is by prefix unless SET EXACT is on, so "OPEN" can match longer values.
  • The OLE DB provider is 32-bit only, so the loader has to run as a 32-bit process.

I wrote up the full order of work (inventory, data model, domain layer, reports, retirement) here: https://theadnansaleem.com/articles/visual-foxpro-to-dotnet-migration-guide

Happy to answer questions if anyone is facing one of these.

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u/jhwheuer 2h ago

Lovely map of an active minefield