Hi daitran,
According to your description, it works well first time. it seems that the code is fine. please check if you pass invalid parameters, which cause the issue.
In addition, this forums is to discuss about data platform development using ADO.NET DataSet and LINQ to DataSet, As your issue is not related to DataSet, we'll move it to Off-Topic forum.
Thanks for your understanding.
Best regards,
Cole Wu
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