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SQL Server error code

SQL Server error 6537

SQL Server raises error 6537 at severity 16, which marks a problem with the query or data that you can correct.

The .NET Framework common language runtime was shut down by user code, such as in a user-defined function or CLR type. SQL Server is shutting down. Environment.Exit should not be used to exit the process. If the intent is to return an integer to indicate failure, use a scalar function or an output parameter instead.
Msg6537
Severity16
Group6000–6999

Source: Database Engine events and errors