Android Question sf = Main.mysql.ExecQueryAsync()

dear all,
sorry bother, I am in a hole and no ideas to go out, please some light. I am consulting a database in MYSQL in order to know if the codbar is in the database or not.
I need to know how capture "something" when the codbar isnt in the DB.

I am using:

' connection to MYSQL
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Main.mysql.InitializeAsync("mysql", Main.driver, Main.jdbcUrl, Main.Username, Main.Password)
Wait For MySQL_Ready (Success As Boolean)

If Success Then
Dim senderfile As Object
senderfile = Main.mysql.ExecQueryAsync("mysql", $"SELECT codbar,descripcion FROM maestro_formatos WHERE codbar= ? "$, Array As String(Main.codbarorigen) )
Wait For (senderfile) mysql_QueryComplete(exito As Boolean, Crsr As JdbcResultSet)

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HOW CAN I CAPTURE WHEN CRSR is null ???? When the CODBAR is not in the database ???

The "EXITO" boolean always has TRUE
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If exito Then

end if
end if

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The connection with MYSqL is ok, but I need to know how capture NULL or something in order to know when the codbar is not in the database.

THANKS A LOT !!!!!!!!!