System.Data.Odbc.OdbcDataReader.OdbcDataReader.GetSchemaTable C# (CSharp) Метод

		DataTable GetSchemaTable ()
		{
			if (IsClosed)
				throw new InvalidOperationException ("The reader is closed.");

			// FIXME : 
			// * Map OdbcType to System.Type and assign to DataType.
			//   This will eliminate the need for IsStringType in
			//   OdbcColumn

			if (_dataTableSchema != null)
				return _dataTableSchema;
			
			DataTable dataTableSchema = null;
			// Only Results from SQL SELECT Queries 
			// get a DataTable for schema of the result
			// otherwise, DataTable is null reference
			if (cols.Length > 0) {
				dataTableSchema = new DataTable ();
				
				dataTableSchema.Columns.Add ("ColumnName", typeof (string));
				dataTableSchema.Columns.Add ("ColumnOrdinal", typeof (int));
				dataTableSchema.Columns.Add ("ColumnSize", typeof (int));
				dataTableSchema.Columns.Add ("NumericPrecision", typeof (int));
				dataTableSchema.Columns.Add ("NumericScale", typeof (int));
				dataTableSchema.Columns.Add ("IsUnique", typeof (bool));
				dataTableSchema.Columns.Add ("IsKey", typeof (bool));
				DataColumn dc = dataTableSchema.Columns["IsKey"];
				dc.AllowDBNull = true; // IsKey can have a DBNull
				dataTableSchema.Columns.Add ("BaseCatalogName", typeof (string));
				dataTableSchema.Columns.Add ("BaseColumnName", typeof (string));
				dataTableSchema.Columns.Add ("BaseSchemaName", typeof (string));
				dataTableSchema.Columns.Add ("BaseTableName", typeof (string));
				dataTableSchema.Columns.Add ("DataType", typeof(Type));
				dataTableSchema.Columns.Add ("AllowDBNull", typeof (bool));
				dataTableSchema.Columns.Add ("ProviderType", typeof (int));
				dataTableSchema.Columns.Add ("IsAliased", typeof (bool));
				dataTableSchema.Columns.Add ("IsExpression", typeof (bool));
				dataTableSchema.Columns.Add ("IsIdentity", typeof (bool));
				dataTableSchema.Columns.Add ("IsAutoIncrement", typeof (bool));
				dataTableSchema.Columns.Add ("IsRowVersion", typeof (bool));
				dataTableSchema.Columns.Add ("IsHidden", typeof (bool));
				dataTableSchema.Columns.Add ("IsLong", typeof (bool));
				dataTableSchema.Columns.Add ("IsReadOnly", typeof (bool));

				DataRow schemaRow;

				for (int i = 0; i < cols.Length; i += 1 ) {
					OdbcColumn col=GetColumn(i);

					schemaRow = dataTableSchema.NewRow ();
					dataTableSchema.Rows.Add (schemaRow);

					schemaRow ["ColumnName"] 	= col.ColumnName;
					schemaRow ["ColumnOrdinal"] 	= i;
					schemaRow ["ColumnSize"] 	= col.MaxLength;
					schemaRow ["NumericPrecision"] 	= GetColumnAttribute (i+1, FieldIdentifier.Precision);
					schemaRow ["NumericScale"] 	= GetColumnAttribute (i+1, FieldIdentifier.Scale);
					schemaRow ["BaseTableName"]   	= GetColumnAttributeStr (i+1, FieldIdentifier.TableName);
					schemaRow ["BaseSchemaName"]  	= GetColumnAttributeStr (i+1, FieldIdentifier.SchemaName);
					schemaRow ["BaseCatalogName"] 	= GetColumnAttributeStr (i+1, FieldIdentifier.CatelogName);
					schemaRow ["BaseColumnName"] 	= GetColumnAttributeStr (i+1, FieldIdentifier.BaseColumnName);
					schemaRow ["DataType"] 		= col.DataType;
					schemaRow ["IsUnique"] 		= false;
					schemaRow ["IsKey"] 		= DBNull.Value;
					schemaRow ["AllowDBNull"] 	= GetColumnAttribute (i+1, FieldIdentifier.Nullable) != libodbc.SQL_NO_NULLS;
					schemaRow ["ProviderType"] 	= (int) col.OdbcType;
					schemaRow ["IsAutoIncrement"] 	= GetColumnAttribute (i+1, FieldIdentifier.AutoUniqueValue) == libodbc.SQL_TRUE;
					schemaRow ["IsExpression"] 	= schemaRow.IsNull ("BaseTableName") || (string) schemaRow ["BaseTableName"] == String.Empty;
					schemaRow ["IsAliased"] 	= (string) schemaRow ["BaseColumnName"] != (string) schemaRow ["ColumnName"];
					schemaRow ["IsReadOnly"] 	= ((bool) schemaRow ["IsExpression"]
									   || GetColumnAttribute (i+1, FieldIdentifier.Updatable) == libodbc.SQL_ATTR_READONLY);

					// FIXME: all of these
					schemaRow ["IsIdentity"] 	= false;
					schemaRow ["IsRowVersion"] 	= false;
					schemaRow ["IsHidden"] 		= false;
					schemaRow ["IsLong"] 		= false;

					// FIXME: according to Brian, 
					// this does not work on MS .NET
					// however, we need it for Mono 
					// for now
					// schemaRow.AcceptChanges();
				}

				// set primary keys
				DataRow [] rows = dataTableSchema.Select ("BaseTableName <> ''",
									  "BaseCatalogName, BaseSchemaName, BaseTableName ASC");

				string lastTableName = String.Empty,
					lastSchemaName = String.Empty,
					lastCatalogName = String.Empty;
				string [] keys = null; // assumed to be sorted.
				foreach (DataRow row in rows) {
					string tableName = (string) row ["BaseTableName"];
					string schemaName = (string) row ["BaseSchemaName"];
					string catalogName = (string) row ["BaseCatalogName"];

					if (tableName != lastTableName || schemaName != lastSchemaName
					    || catalogName != lastCatalogName)
						keys = GetPrimaryKeys (catalogName, schemaName, tableName);
				
					if (keys != null &&
					    Array.BinarySearch (keys, (string) row ["BaseColumnName"]) >= 0) {
						row ["IsKey"] = true;
						row ["IsUnique"] = true;
						row ["AllowDBNull"] = false;
						GetColumn ( ColIndex ( (string) row ["ColumnName"])).AllowDBNull = false;
					}
					lastTableName = tableName;
					lastSchemaName = schemaName;
					lastCatalogName = catalogName;
				}
				dataTableSchema.AcceptChanges ();
			}
			return (_dataTableSchema = dataTableSchema);
		}