System.Data.Select.CreateIndex C# (CSharp) Méthode

        private void CreateIndex()
        {
            if (_index == null)
            {
                if (_nCandidates == 0)
                {
                    _index = new Index(_table, _indexFields, _recordStates, null);
                    _index.AddRef();
                }
                else
                {
                    int i;
                    int lenCanColumns = _candidateColumns.Length;
                    int lenIndexDesc = _indexFields.Length;
                    bool equalsOperator = true;
                    for (i = 0; i < lenCanColumns; i++)
                    {
                        if (_candidateColumns[i] != null)
                        {
                            if (!_candidateColumns[i].equalsOperator)
                            {
                                equalsOperator = false;
                                break;
                            }
                        }
                    }

                    int j = 0;
                    for (i = 0; i < lenIndexDesc; i++)
                    {
                        ColumnInfo candidateColumn = _candidateColumns[_indexFields[i].Column.Ordinal];
                        if (candidateColumn != null)
                        {
                            candidateColumn.flag = true;
                            j++;
                        }
                    }
                    int indexNotInCandidates = lenIndexDesc - j;
                    int candidatesNotInIndex = _nCandidates - j;
                    IndexField[] ndxFields = new IndexField[_nCandidates + indexNotInCandidates];

                    if (equalsOperator)
                    {
                        j = 0;
                        for (i = 0; i < lenCanColumns; i++)
                        {
                            if (_candidateColumns[i] != null)
                            {
                                ndxFields[j++] = new IndexField(_table.Columns[i], isDescending: false);
                                _candidateColumns[i].flag = false;// this means it is processed
                            }
                        }
                        for (i = 0; i < lenIndexDesc; i++)
                        {
                            ColumnInfo canColumn = _candidateColumns[_indexFields[i].Column.Ordinal];
                            if (canColumn == null || canColumn.flag)
                            { // if sort column is not a filter col , or not processed
                                ndxFields[j++] = _indexFields[i];
                                if (canColumn != null)
                                {
                                    canColumn.flag = false;
                                }
                            }
                        }

                        for (i = 0; i < _candidateColumns.Length; i++)
                        {
                            if (_candidateColumns[i] != null)
                            {
                                _candidateColumns[i].flag = false;// same as before, it is false when it returns 
                            }
                        }

                        // Debug.Assert(j == candidatesNotInIndex, "Whole ndxDesc should be filled!");

                        _index = new Index(_table, ndxFields, _recordStates, null);
                        if (!IsOperatorIn(_expression))
                        {
                            // if the expression contains an 'IN' operator, the index will not be shared
                            // therefore we do not need to index.AddRef, also table would track index consuming more memory until first write
                            _index.AddRef();
                        }


                        _matchedCandidates = _nCandidates;
                    }
                    else
                    {
                        for (i = 0; i < lenIndexDesc; i++)
                        {
                            ndxFields[i] = _indexFields[i];
                            ColumnInfo canColumn = _candidateColumns[_indexFields[i].Column.Ordinal];
                            if (canColumn != null)
                                canColumn.flag = true;
                        }
                        j = i;
                        for (i = 0; i < lenCanColumns; i++)
                        {
                            if (_candidateColumns[i] != null)
                            {
                                if (!_candidateColumns[i].flag)
                                {
                                    ndxFields[j++] = new IndexField(_table.Columns[i], isDescending: false);
                                }
                                else
                                {
                                    _candidateColumns[i].flag = false;
                                }
                            }
                        }
                        //                        Debug.Assert(j == nCandidates+indexNotInCandidates, "Whole ndxDesc should be filled!");

                        _index = new Index(_table, ndxFields, _recordStates, null);
                        _matchedCandidates = 0;
                        if (_linearExpression != _expression)
                        {
                            IndexField[] fields = _index._indexFields;
                            while (_matchedCandidates < j)
                            {
                                ColumnInfo canColumn = _candidateColumns[fields[_matchedCandidates].Column.Ordinal];
                                if (canColumn == null || canColumn.expr == null)
                                    break;
                                _matchedCandidates++;
                                if (!canColumn.equalsOperator)
                                    break;
                            }
                        }
                        for (i = 0; i < _candidateColumns.Length; i++)
                        {
                            if (_candidateColumns[i] != null)
                            {
                                _candidateColumns[i].flag = false;// same as before, it is false when it returns 
                            }
                        }
                    }
                }
            }
        }