System.Data.DataRow.HasChanges C# (CSharp) Method

        internal bool HasChanges()
        {
            if (!HasVersion(DataRowVersion.Original) || !HasVersion(DataRowVersion.Current))
            {
                return true; // if does not have original, its added row, if does not have current, its deleted row so it has changes
            }
            foreach (DataColumn dc in Table.Columns)
            {
                if (dc.Compare(_oldRecord, _newRecord) != 0)
                {
                    return true;
                }
            }
            return false;
        }

        private void SetDataRowWithLoadOption (DataRow dataRow, int recordNo, LoadOption loadOption, bool checkReadOnly) {
            bool hasError = false;
            if (checkReadOnly) {
                foreach(DataColumn dc in this.Columns) {
                    if (dc.ReadOnly && !dc.Computed) {
                        switch(loadOption) {
                            case LoadOption.OverwriteChanges:
                                if ((dataRow[dc, DataRowVersion.Current] != dc[recordNo]) ||(dataRow[dc, DataRowVersion.Original] != dc[recordNo]))
                                    hasError = true;
                                break;
                            case LoadOption.Upsert:
                                if (dataRow[dc, DataRowVersion.Current] != dc[recordNo])
                                    hasError = true;
                                break;
                            case LoadOption.PreserveChanges:
                                if (dataRow[dc, DataRowVersion.Original] != dc[recordNo])
                                    hasError = true;
                                break;
                        }
                    }
                }
            } // No Event should be fired  in SenNewRecord and SetOldRecord
            // fire rowChanging event here

            DataRowChangeEventArgs drcevent = null;
            DataRowAction action = DataRowAction.Nothing;
            int cacheTempRecord = dataRow.tempRecord;
            dataRow.tempRecord = recordNo;

            switch(loadOption) {
                case LoadOption.OverwriteChanges:
                    action = DataRowAction.ChangeCurrentAndOriginal;
                    break;
                case LoadOption.Upsert:
                    switch(dataRow.RowState) {
                        case DataRowState.Unchanged:
                            // let see if the incomming value has the same values as existing row, so compare records
                            foreach(DataColumn dc in dataRow.Table.Columns) {
                                if (0 != dc.Compare(dataRow.newRecord, recordNo)) {
                                    action = DataRowAction.Change;
                                    break;
                                }
                            }
                            break;
                        case DataRowState.Deleted:
                            Debug.Assert(false, "LoadOption.Upsert with deleted row, should not be here");
                            break;
                        default :
                            action = DataRowAction.Change;
                            break;
                    }
                    break;
                case LoadOption.PreserveChanges:
                    switch(dataRow.RowState) {
                        case DataRowState.Unchanged:
                            action = DataRowAction.ChangeCurrentAndOriginal;
                            break;
                        default:
                            action = DataRowAction.ChangeOriginal;
                            break;
                    }
                    break;
                default:
                    throw ExceptionBuilder.ArgumentOutOfRange("LoadOption");
            }

            try {
                drcevent = RaiseRowChanging(null, dataRow, action);
                if (action == DataRowAction.Nothing) { // RaiseRowChanging does not fire for DataRowAction.Nothing
                    dataRow.inChangingEvent = true;
                    try {
                        drcevent = OnRowChanging(drcevent, dataRow, action);
                    }
                    finally {
                        dataRow.inChangingEvent = false;
                    }
                }
            }
            finally {
                Debug.Assert(dataRow.tempRecord == recordNo, "tempRecord has been changed in event handler");
                if (DataRowState.Detached == dataRow.RowState) {
                    // 'row.Table.Remove(row);'
                    if (-1 != cacheTempRecord) {
                        FreeRecord(ref cacheTempRecord);
                    }
                }
                else {
                    if (dataRow.tempRecord != recordNo) {
                        // 'row.EndEdit(); row.BeginEdit(); '
                        if (-1 != cacheTempRecord) {
                            FreeRecord(ref cacheTempRecord);
                        }
                        if (-1 != recordNo) {
                            FreeRecord(ref recordNo);
                        }
                        recordNo = dataRow.tempRecord;
                    }
                    else {
                        dataRow.tempRecord = cacheTempRecord;
                    }
                }
            }
            if (dataRow.tempRecord != -1) {
                dataRow.CancelEdit();
            }

            switch(loadOption) {
                case LoadOption.OverwriteChanges:
                     this.SetNewRecord(dataRow,  recordNo, DataRowAction.Change, false, false);
                     this.SetOldRecord(dataRow,  recordNo);
                     break;
                case LoadOption.Upsert:
                     if (dataRow.RowState == DataRowState.Unchanged) {
                         this.SetNewRecord(dataRow,  recordNo, DataRowAction.Change, false, false);
                         if (!dataRow.HasChanges()) {
                             this.SetOldRecord(dataRow, recordNo);
                         }
                     }
                     else {
                         if (dataRow.RowState == DataRowState.Deleted)
                             dataRow.RejectChanges();
                         this.SetNewRecord(dataRow,  recordNo, DataRowAction.Change, false, false);
                     }
                     break;
                case LoadOption.PreserveChanges:
                     if (dataRow.RowState == DataRowState.Unchanged) {
                         // SQLBU 500706: DataTable internal index is corrupted: '8'
                         // if ListChanged event deletes dataRow
                         this.SetOldRecord(dataRow,  recordNo); // do not fire event
                         this.SetNewRecord(dataRow, recordNo, DataRowAction.Change, false, false);
                     }
                     else { // if modified/ added / deleted we want this operation to fire event (just for LoadOption.PreserveCurrentValues)
                        this.SetOldRecord(dataRow,  recordNo);
                     }
                     break;
                default:
                    throw ExceptionBuilder.ArgumentOutOfRange("LoadOption");
            }

            if (hasError) {
                string error = Res.GetString(Res.Load_ReadOnlyDataModified);
                if (dataRow.RowError.Length == 0) { // WebData 112272, append the row error
                    dataRow.RowError = error;
                }
                else {
                    dataRow.RowError += " ]:[ " + error ;
                }

                foreach(DataColumn dc in this.Columns) {
                    if (dc.ReadOnly && !dc.Computed)
                        dataRow.SetColumnError(dc, error);
                }
            }

            drcevent = RaiseRowChanged(drcevent, dataRow, action);
            if (action == DataRowAction.Nothing) { // RaiseRowChanged does not fire for DataRowAction.Nothing
                dataRow.inChangingEvent = true;
                try {
                    OnRowChanged(drcevent, dataRow, action);
                }
                finally {
                    dataRow.inChangingEvent = false;
                }
            }

        }