To represent an hierarchy in the report, you must specify the value of the MasterKeyDataColumn property. This property is required for filling. If the value of the MasterKeyDataColumn is not specified, the report generator cannot determine the hierarchy in the report. The value of this property will be a data column from the selected Hierarchical band of the data source, which entries are the master key for creating an hierarchy in the report. For example, if the Employees data source is specified for the Hierarchical band, then the MasterKeyDataColumn property is the ReportsTo column data. The values of this data column are used to specify to what this element in the table is subordinated. Usually, this column indicates the keys in the data column, which is a value of the KeyDataColumn property. The picture below shows the scheme of an hierarchy of the ReportsTo data column:
