DbSchemaTable.cs

Go to the documentation of this file.

namespace System.Data.Common;
 
internal sealed class DbSchemaTable
{
    private enum ColumnEnum
    {
        ColumnName,
        ColumnOrdinal,
        ColumnSize,
        BaseServerName,
        BaseCatalogName,
        BaseColumnName,
        BaseSchemaName,
        BaseTableName,
        IsAutoIncrement,
        IsUnique,
        IsKey,
        IsRowVersion,
        DataType,
        ProviderSpecificDataType,
        AllowDBNull,
        ProviderType,
        IsExpression,
        IsHidden,
        IsLong,
        IsReadOnly,
        SchemaMappingUnsortedIndex
    }
 
    private static readonly string[] s_DBCOLUMN_NAME = new string[21]
    {
        SchemaTableColumn.ColumnName,
        SchemaTableColumn.ColumnOrdinal,
        SchemaTableColumn.ColumnSize,
        SchemaTableOptionalColumn.BaseServerName,
        SchemaTableOptionalColumn.BaseCatalogName,
        SchemaTableColumn.BaseColumnName,
        SchemaTableColumn.BaseSchemaName,
        SchemaTableColumn.BaseTableName,
        SchemaTableOptionalColumn.IsAutoIncrement,
        SchemaTableColumn.IsUnique,
        SchemaTableColumn.IsKey,
        SchemaTableOptionalColumn.IsRowVersion,
        SchemaTableColumn.DataType,
        SchemaTableOptionalColumn.ProviderSpecificDataType,
        SchemaTableColumn.AllowDBNull,
        SchemaTableColumn.ProviderType,
        SchemaTableColumn.IsExpression,
        SchemaTableOptionalColumn.IsHidden,
        SchemaTableColumn.IsLong,
        SchemaTableOptionalColumn.IsReadOnly,
        "SchemaMapping Unsorted Index"
    };
 
    internal DataTable _dataTable;
 
    private readonly DataColumnCollection _columns;
 
    private readonly DataColumn[] _columnCache = new DataColumn[s_DBCOLUMN_NAME.Length];
 
    private readonly bool _returnProviderSpecificTypes;
 
    internal DataColumn ColumnName => CachedDataColumn(ColumnEnum.ColumnName);
 
    internal DataColumn Size => CachedDataColumn(ColumnEnum.ColumnSize);
 
    internal DataColumn BaseServerName => CachedDataColumn(ColumnEnum.BaseServerName);
 
    internal DataColumn BaseColumnName => CachedDataColumn(ColumnEnum.BaseColumnName);
 
    internal DataColumn BaseTableName => CachedDataColumn(ColumnEnum.BaseTableName);
 
    internal DataColumn BaseCatalogName => CachedDataColumn(ColumnEnum.BaseCatalogName);
 
    internal DataColumn BaseSchemaName => CachedDataColumn(ColumnEnum.BaseSchemaName);
 
    internal DataColumn IsAutoIncrement => CachedDataColumn(ColumnEnum.IsAutoIncrement);
 
    internal DataColumn IsUnique => CachedDataColumn(ColumnEnum.IsUnique);
 
    internal DataColumn IsKey => CachedDataColumn(ColumnEnum.IsKey);
 
    internal DataColumn IsRowVersion => CachedDataColumn(ColumnEnum.IsRowVersion);
 
    internal DataColumn AllowDBNull => CachedDataColumn(ColumnEnum.AllowDBNull);
 
    internal DataColumn IsExpression => CachedDataColumn(ColumnEnum.IsExpression);
 
    internal DataColumn IsHidden => CachedDataColumn(ColumnEnum.IsHidden);
 
    internal DataColumn IsLong => CachedDataColumn(ColumnEnum.IsLong);
 
    internal DataColumn IsReadOnly => CachedDataColumn(ColumnEnum.IsReadOnly);
 
    internal DataColumn UnsortedIndex => CachedDataColumn(ColumnEnum.SchemaMappingUnsortedIndex);
 
    internal DataColumn DataType
    {
        get
        {
            if (_returnProviderSpecificTypes)
            {
                return CachedDataColumn(ColumnEnum.ProviderSpecificDataType, ColumnEnum.DataType);
            }
            return CachedDataColumn(ColumnEnum.DataType);
        }
    }
 
    internal DbSchemaTable(DataTable dataTable, bool returnProviderSpecificTypes)
    {
        _dataTable = dataTable;
        _columns = dataTable.Columns;
        _returnProviderSpecificTypes = returnProviderSpecificTypes;
    }
 
    private DataColumn CachedDataColumn(ColumnEnum column)
    {
        return CachedDataColumn(column, column);
    }
 
    private DataColumn CachedDataColumn(ColumnEnum column, ColumnEnum column2)
    {
        DataColumn dataColumn = _columnCache[(int)column];
        if (dataColumn == null)
        {
            int num = _columns.IndexOf(s_DBCOLUMN_NAME[(int)column]);
            if (-1 == num && column != column2)
            {
                num = _columns.IndexOf(s_DBCOLUMN_NAME[(int)column2]);
            }
            if (-1 != num)
            {
                dataColumn = _columns[num];
                _columnCache[(int)column] = dataColumn;
            }
        }
        return dataColumn;
    }
}