MSDN Documentation

DataViews

The DataView class in ADO.NET provides a way to sort and filter DataTable data. It acts as a programmable view of the data in a DataTable, allowing you to present the data in different ways without modifying the underlying DataTable itself.

Key Features of DataView

• Sorting: You can sort the data in a DataView based on one or more columns.
• Filtering: You can filter the data to display only rows that meet specific criteria.
• Dynamic Updates: A DataView automatically reflects changes made to the underlying DataTable.
• Row State Filtering: You can filter based on the current state of rows (e.g., Added, Modified, Deleted, Unchanged).
• Data Binding: DataView objects are commonly used for data binding to UI controls like grids.

Creating and Using a DataView

To create a DataView, you instantiate the DataView class and pass the DataTable you want to view to its constructor. You can then set properties like Sort and RowFilter to configure the view.

Example: Sorting and Filtering

Let's assume you have a DataTable named productsTable with columns like ProductID, ProductName, and UnitPrice.

// Assume productsTable is already populated with data

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

// Sort the DataView by ProductName in ascending order
dataView.Sort = "ProductName ASC";

// Filter the DataView to show products with UnitPrice greater than 50
dataView.RowFilter = "UnitPrice > 50";

// Now, iterate through the filtered and sorted data
foreach (DataRowView rowView in dataView)
{
    Console.WriteLine($"Product: {rowView["ProductName"]}, Price: {rowView["UnitPrice"]}");
}
            

Key Properties

• RowFilter: A string expression used to filter rows. The syntax is similar to the WHERE clause in SQL.
• Sort: A string expression used to sort rows. The syntax is similar to the ORDER BY clause in SQL.
• DataViewManager: Gets or sets the DataViewManager associated with this DataView.
• Table: Gets the DataTable that this DataView is based on.
• AllowNew: Gets or sets a value indicating whether new rows can be added through this DataView.
• AllowEdit: Gets or sets a value indicating whether existing rows can be edited through this DataView.
• AllowDelete: Gets or sets a value indicating whether rows can be deleted through this DataView.

RowFilter Syntax

The RowFilter property uses an expression language to define filtering criteria. Here are some examples:

• "City = 'London'": Selects rows where the City column is 'London'.
• "Age > 30": Selects rows where the Age column is greater than 30.
• "LastName LIKE 'S%'": Selects rows where the LastName starts with 'S'.
• "OrderDate BETWEEN '2023-01-01' AND '2023-12-31'": Selects rows within a date range.
• "AND" and "OR" operators can be used to combine conditions.

Sort Syntax

The Sort property uses an expression language to define sorting order. Here are some examples:

• "ProductName ASC": Sorts by ProductName in ascending order.
• "UnitPrice DESC": Sorts by UnitPrice in descending order.
• "Category ASC, UnitPrice DESC": Sorts by Category ascending, then by UnitPrice descending for rows with the same category.

Conclusion

DataView is a powerful tool for manipulating and presenting data from a DataTable in ADO.NET. Its ability to sort, filter, and reflect changes dynamically makes it indispensable for data-driven applications.