DataView Objects

The DataView object provides a way to view and interact with data stored in a DataTable. It acts as a dynamic view on the DataTable, allowing you to filter, sort, and navigate through the data without modifying the underlying DataTable itself. This is particularly useful for data binding scenarios and for presenting specific subsets of data to the user.

Key Features of DataView

• Filtering: You can define filter expressions to select specific rows from the DataTable based on criteria.
• Sorting: You can specify sort orders for columns to arrange the data in a desired sequence.
• Dynamic Updates: When the underlying DataTable changes, the DataView automatically reflects these changes.
• Current Row Management: Provides properties and methods to manage the current row within the view.
• Change Notifications: Can notify other objects when its data or view state changes, enabling responsive user interfaces.

Creating and Using a DataView

To create a DataView, you typically instantiate it with a DataTable. You can then configure its properties for filtering and sorting.

using System;
using System.Data;

// Assume 'dataTable' is an existing DataTable object populated with data.
DataTable dataTable = new DataTable("Products");
dataTable.Columns.Add("ProductID", typeof(int));
dataTable.Columns.Add("ProductName", typeof(string));
dataTable.Columns.Add("Category", typeof(string));
dataTable.Columns.Add("Price", typeof(decimal));

dataTable.Rows.Add(1, "Laptop", "Electronics", 1200.00m);
dataTable.Rows.Add(2, "Mouse", "Electronics", 25.00m);
dataTable.Rows.Add(3, "Keyboard", "Electronics", 75.00m);
dataTable.Rows.Add(4, "Desk Chair", "Furniture", 150.00m);
dataTable.Rows.Add(5, "Monitor", "Electronics", 300.00m);

// Create a DataView from the DataTable
DataView dataView = new DataView(dataTable);

// Set a filter expression to show only electronics
dataView.RowFilter = "Category = 'Electronics'";

// Set a sort order
dataView.Sort = "Price DESC";

// Iterate through the filtered and sorted data
Console.WriteLine("Filtered and Sorted Electronics Products:");
foreach (DataRowView rowView in dataView)
{
    Console.WriteLine($"  {rowView["ProductName"]} - ${rowView["Price"]}");
}
            

DataView Properties

The following are some of the most commonly used properties of the DataView object:

DataViewRowState

When working with DataView, you can also specify which row states to include. This is done using the DataViewRowState enumeration, which can be combined with the RowFilter. Common states include:

• CurrentRows: Includes only the current rows.
• Deleted: Includes only deleted rows.
• ModifiedCurrent: Includes only modified current rows.
• ModifiedOriginal: Includes only modified original rows.
• OriginalRows: Includes only the original rows.
• AllRows: Includes all rows, including original and current versions.

// Example: Show only modified rows
dataView.RowStateFilter = DataViewRowState.ModifiedCurrent;
            

Conclusion

The DataView object is a powerful tool for manipulating and presenting data from a DataTable. Its ability to filter, sort, and dynamically update makes it an essential component for building data-driven applications in ADO.NET.