SqlException

If the exception is:
System.Data.SqlClient.SqlException: Timeout expired. The timeout period elapsed prior to completion of the operation or the server is not responding. at System.Data.SqlClient.SqlConnection.OnError(SqlException exception, Boolean breakConnection)

solution
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It means Command is taking long in the database and has been killed. The default time of 30 seconds should be increased by using the "CommandTimeout" field on the "Command" object.

e,g

SqlCommand sqlcom = connection.CreateCommand();
sqlcom.CommandTimeout = 60; // Increase according to requirement
sqlcom.CommandText = sqlText;