DataView Class

The DataView class in ADO.NET provides a way to create a custom view of a DataTable. It allows you to filter, sort, and navigate through the rows of a DataTable without modifying the original data. This is particularly useful for data-bound controls that need to display specific subsets or sorted orders of data.

Overview

A DataView is a dynamic view of the data contained in a DataTable. Changes made to the underlying DataTable are immediately reflected in the DataView, and vice-versa, allowing for real-time data manipulation.

Key features of DataView include:

• Filtering: You can filter the rows based on specified criteria.
• Sorting: You can sort the rows by one or more columns.
• Row State Filtering: You can choose to view only current, original, or deleted rows.
• Data Binding: Easily used with data-bound controls like DataGridView, ListBox, etc.

Creating a DataView

To create a DataView, you instantiate the DataView class, passing the DataTable you want to view as a constructor argument.

// Assume 'myDataTable' is an existing DataTable object
DataView myDataView = new DataView(myDataTable);
            

Filtering Data

The RowFilter property is used to specify a filter expression. The expression syntax is similar to the `WHERE` clause in SQL.

// Filter to show only rows where 'City' is 'London'
myDataView.RowFilter = "City = 'London'";

// Filter to show rows where 'Age' is greater than 30
myDataView.RowFilter = "Age > 30";

// Filter with multiple conditions
myDataView.RowFilter = "Country = 'USA' AND Age > 25";
            

Sorting Data

The Sort property is used to specify the sorting order. The expression syntax is similar to the `ORDER BY` clause in SQL.

// Sort by 'LastName' in ascending order
myDataView.Sort = "LastName ASC";

// Sort by 'Age' in descending order
myDataView.Sort = "Age DESC";

// Sort by multiple columns
myDataView.Sort = "Country ASC, City DESC";
            

Row State Filtering

The RowStateFilter property allows you to specify which versions of rows to display.

• DataViewRowState.CurrentRows: Shows the current state of rows (default).
• DataViewRowState.OriginalRows: Shows the original state of rows before any modifications.
• DataViewRowState.Deleted: Shows rows that have been deleted.
• DataViewRowState.Added: Shows rows that have been added.
• DataViewRowState.ModifiedCurrent: Shows modified rows in their current state.
• DataViewRowState.ModifiedOriginal: Shows modified rows in their original state.

// Show only the original rows
myDataView.RowStateFilter = DataViewRowState.OriginalRows;
            

Data Binding Example

Here's a simple example of how you might bind a DataView to a DataGridView in a Windows Forms application.

// Assuming you have a DataGridView named 'dataGridView1'
// and a DataTable named 'customersTable' populated with data

DataView customerView = new DataView(customersTable);
customerView.RowFilter = "Country = 'UK'";
customerView.Sort = "CompanyName ASC";

dataGridView1.DataSource = customerView;
                

Properties Summary

See Also

• DataTable Class
• Data Binding in ADO.NET
• Filtering Data in ADO.NET