WebService, C# เรียกใช้ Webservice ไม่ได้ค่ะ ติด Error ช่วยดูให้หน่อยค่ะว่าเป็นเพราะอะไร ????

System.Data.ConstraintException: Failed to enable constraints. One or more rows contain values violating non-null, unique, or foreign-key constraints.
at System.Data.DataTable.EnableConstraints()
at System.Data.DataTable.set_EnforceConstraints(Boolean value)
at System.Data.DataTable.EndLoadData()
at System.Data.Common.DataAdapter.FillFromReader(DataSet dataset, DataTable datatable, String srcTable, DataReaderContainer dataReader, Int32 startRecord, Int32 maxRecords, DataColumn parentChapterColumn, Object parentChapterValue)
at System.Data.Common.DataAdapter.Fill(DataTable[] dataTables, IDataReader dataReader, Int32 startRecord, Int32 maxRecords)
at System.Data.Common.DbDataAdapter.FillInternal(DataSet dataset, DataTable[] datatables, Int32 startRecord, Int32 maxRecords, String srcTable, IDbCommand command, CommandBehavior behavior)
at System.Data.Common.DbDataAdapter.Fill(DataTable[] dataTables, Int32 startRecord, Int32 maxRecords, IDbCommand command, CommandBehavior behavior)
at System.Data.Common.DbDataAdapter.Fill(DataTable dataTable)
at DataSet1TableAdapters.OrderTableAdapter.GetDataOrder_IDTable(Nullable`1 ID) in c:\Windows\Microsoft.NET\Framework\v2.0.50727\Temporary ASP.NET Files\orderentry\b3e862cd\9afc9a7c\App_Code.0fhr_w-v.1.cs:line 4478
at Service.GetDataOrder_IDTable(Int32 ID) in d:\Project\OrderEntry\WebService\App_Code\Service.cs:line 88

ใช้ Web Service ไปเรียก Class สำหรับติดต่อ ฐานข้อมูล ค่ะ