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»Spread for Windows Forms » Product Tour » Models » Data Understanding the Data Model   Back to Top  Data Model The data model includes the contents of the cells, whether it is the value or the formula in a cell, or the cell notes or cell tags. This includes the Value properties for cells in the data area of the spreadsheet, the database properties for data-bound spreadsheets, and anything having to do with the contents in the cells. The data model is an object that supplies the cell values being displayed in the sheet. In most cases, you can simply use the default data model that is created when the sheet is created. The default data model can be used in unbound or bound modes. In unbound mode, the data model acts much like a two dimensional array of cell values. In bound mode, the data model wraps the supplied DataSource and if needed can supply additional settings not available from the DataSource, for example, cell formulas, and unbound rows or columns. The DefaultSheetDataModel creates objects to store notes, formulas, tags, and values, and those objects are designed to balance memory usage versus speed based on how big the model is and how sparse the data in the model is. If you are not using notes, formulas, and tags, then not much memory is used since the sparsity of the data is high. In fact, those objects do not allocate any memory for data until it is actually needed, so as long as there are no notes, formulas, or tags set into the model, memory usage remains low. If you derive from DefaultSheetDataModel and use that implementation of GetValue and SetValue to store the data, then it will use our implementation of sparse arrays and matrices to balance the memory usage with the access speed. It is designed to make it very fast to create a very large model (that is, 2 billion rows by 2 billion columns) and keep it reasonably fast to get and set values into it.

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