DataView
Class
Definition
Represents a databindable, customized view of a DataTable for sorting, filtering, searching, editing, and navigation. The DataView does not store data, but instead represents a connected view of its corresponding DataTable. Changes to the DataView’s data will affect the DataTable. Changes to the DataTable’s data will affect all DataViews associated with it.
public class DataView : System.ComponentModel.MarshalByValueComponent, System.Collections.IList, System.ComponentModel.IBindingListView, System.ComponentModel.ISupportInitializeNotification, System.ComponentModel.ITypedList
- Inheritance
- Implements
Inherited Members
System.ComponentModel.MarshalByValueComponent
System.Object
Examples
The following example creates a single DataTable with one column and five rows. Two DataView objects are created and the RowStateFilter is set on each to show different views of the table data. The values are then printed.
using System;
using System.Xml;
using System.Data;
using System.Data.Common;
using System.Windows.Forms;
public class Form1: Form
{
protected DataSet DataSet1;
protected DataGrid dataGrid1;
private void DemonstrateDataView()
{
// Create one DataTable with one column.
DataTable table = new DataTable("table");
DataColumn colItem = new DataColumn("item",
Type.GetType("System.String"));
table.Columns.Add(colItem);
// Add five items.
DataRow NewRow;
for(int i = 0; i <5; i++)
{
NewRow = table.NewRow();
NewRow["item"] = "Item " + i;
table.Rows.Add(NewRow);
}
// Change the values in the table.
table.AcceptChanges();
table.Rows[0]["item"]="cat";
table.Rows[1]["item"] = "dog";
// Create two DataView objects with the same table.
DataView firstView = new DataView(table);
DataView secondView = new DataView(table);
// Print current table values.
PrintTableOrView(table,"Current Values in Table");
// Set first DataView to show only modified
// versions of original rows.
firstView.RowStateFilter=DataViewRowState.ModifiedOriginal;
// Print values.
PrintTableOrView(firstView,"First DataView: ModifiedOriginal");
// Add one New row to the second view.
DataRowView rowView;
rowView=secondView.AddNew();
rowView["item"] = "fish";
// Set second DataView to show modified versions of
// current rows, or New rows.
secondView.RowStateFilter=DataViewRowState.ModifiedCurrent
| DataViewRowState.Added;
// Print modified and Added rows.
PrintTableOrView(secondView,
"Second DataView: ModifiedCurrent | Added");
}
private void PrintTableOrView(DataTable table, string label)
{
// This function prints values in the table or DataView.
Console.WriteLine("\n" + label);
for(int i = 0; i<table.Rows.Count;i++)
{
Console.WriteLine("\table" + table.Rows[i]["item"]);
}
Console.WriteLine();
}
private void PrintTableOrView(DataView view, string label)
{
// This overload prints values in the table or DataView.
Console.WriteLine("\n" + label);
for(int i = 0; i<view.Count;i++)
{
Console.WriteLine("\table" + view[i]["item"]);
}
Console.WriteLine();
}
}
Private Sub DemonstrateDataView()
' Create one DataTable with one column.
Dim table As DataTable = New DataTable("table")
Dim colItem As DataColumn = New DataColumn("item", _
Type.GetType("System.String"))
table.Columns.Add(colItem)
' Add five items.
Dim NewRow As DataRow
Dim i As Integer
For i = 0 To 4
NewRow = table.NewRow()
NewRow("item") = "Item " & i
table.Rows.Add(NewRow)
Next
table.AcceptChanges()
' Create two DataView objects with the same table.
Dim firstView As DataView = New DataView(table)
Dim secondView As DataView = New DataView(table)
' Change the values in the table.
table.Rows(0)("item") = "cat"
table.Rows(1)("item") = "dog"
' Print current table values.
PrintTableOrView(table, "Current Values in Table")
' Set first DataView to show only modified versions of original rows.
firstView.RowStateFilter = DataViewRowState.ModifiedOriginal
' Print values.
PrintTableOrView(firstView, "First DataView: ModifiedOriginal")
' Add one New row to the second view.
Dim rowView As DataRowView
rowView = secondView.AddNew()
rowView("item") = "fish"
' Set second DataView to show modified versions of
' current rows, or New rows.
secondView.RowStateFilter = DataViewRowState.ModifiedCurrent _
Or DataViewRowState.Added
' Print modified and Added rows.
PrintTableOrView(secondView, _
"Second DataView: ModifiedCurrent or Added")
End Sub
Overloads Private Sub PrintTableOrView( _
ByVal view As DataView, ByVal label As String)
Console.WriteLine(label)
Dim i As Integer
For i = 0 To view.count - 1
Console.WriteLine(view(i)("item"))
Next
Console.WriteLine()
End Sub
Overloads Private Sub PrintTableOrView( _
ByVal table As DataTable, ByVal label As String)
Console.WriteLine(label)
Dim i As Integer
For i = 0 To table.Rows.Count - 1
Console.WriteLine(table.Rows(i)("item"))
Next
Console.WriteLine()
End Sub
The following example creates a DataView of online orders ordered by total due from a LINQ to DataSet query:
DataTable orders = dataSet.Tables["SalesOrderHeader"];
EnumerableRowCollection<DataRow> query =
from order in orders.AsEnumerable()
where order.Field<bool>("OnlineOrderFlag") == true
orderby order.Field<decimal>("TotalDue")
select order;
DataView view = query.AsDataView();
bindingSource1.DataSource = view;
Dim orders As DataTable = dataSet.Tables("SalesOrderHeader")
Dim query = _
From order In orders.AsEnumerable() _
Where order.Field(Of Boolean)("OnlineOrderFlag") = True _
Order By order.Field(Of Decimal)("TotalDue") _
Select order
Dim view As DataView = query.AsDataView()
bindingSource1.DataSource = view
Remarks
A major function of the DataView is to allow for data binding on both Windows Forms and Web Forms.
Additionally, a DataView can be customized to present a subset of data from the DataTable. This capability lets you have two controls bound to the same DataTable, but that show different versions of the data. For example, one control might be bound to a DataView that shows all the rows in the table, and a second might be configured to display only the rows that have been deleted from the DataTable. The DataTable also has a DefaultView property. This returns the default DataView for the table. For example, if you want to create a custom view on the table, set the RowFilter on the DataView returned by the DefaultView.
To create a filtered and sorted view of data, set the RowFilter and Sort properties. Then, use the Item[Int32] property to return a single DataRowView.
You can also add and delete from the set of rows using the AddNew and Delete methods. When you use those methods, the RowStateFilter property can set to specify that only deleted rows or new rows be displayed by the DataView.
Note
If you do not explicitly specify sort criteria for DataView, the DataRowView objects in DataView are sorted based on the index of DataView's corresponding DataRow in the DataTable.Rows DataRowCollection.
LINQ to DataSet allows developers to create complex, powerful queries over a DataSet by using LINQ. A LINQ to DataSet query returns an enumeration of DataRow objects, however, which is not easily used in a binding scenario. DataView can be created from a LINQ to DataSet query and takes on the filtering and sorting characteristics of that query. LINQ to DataSet extends the functionality of the DataView by providing LINQ expression-based filtering and sorting, which allows for much more complex and powerful filtering and sorting operations than string-based filtering and sorting. See Data Binding and LINQ to DataSet for more information.
Constructors
| DataView() |
Initializes a new instance of the DataView class. |
| DataView(DataTable) |
Initializes a new instance of the DataView class with the specified DataTable. |
| DataView(DataTable, String, String, DataViewRowState) |
Initializes a new instance of the DataView class with the specified DataTable, RowFilter, Sort, and DataViewRowState. |
Properties
| AllowDelete |
Sets or gets a value that indicates whether deletes are allowed. |
| AllowEdit |
Gets or sets a value that indicates whether edits are allowed. |
| AllowNew |
Gets or sets a value that indicates whether the new rows can be added by using the AddNew() method. |
| ApplyDefaultSort |
Gets or sets a value that indicates whether to use the default sort. The default sort is (ascending) by all primary keys as specified by PrimaryKey. |
| Count |
Gets the number of records in the DataView after RowFilter and RowStateFilter have been applied. |
| DataViewManager |
Gets the DataViewManager associated with this view. |
| IsInitialized |
Gets a value that indicates whether the component is initialized. |
| IsOpen |
Gets a value that indicates whether the data source is currently open and projecting views of data on the DataTable. |
| Item[Int32] |
Gets a row of data from a specified table. |
| RowFilter |
Gets or sets the expression used to filter which rows are viewed in the DataView. |
| RowStateFilter |
Gets or sets the row state filter used in the DataView. |
| Sort |
Gets or sets the sort column or columns, and sort order for the DataView. |
| Table |
Gets or sets the source DataTable. |
Methods
| AddNew() |
Adds a new row to the DataView. |
| BeginInit() |
Starts the initialization of a DataView that is used on a form or used by another component. The initialization occurs at runtime. |
| Close() |
Closes the DataView. |
| ColumnCollectionChanged(Object, CollectionChangeEventArgs) |
Occurs after a DataColumnCollection has been changed successfully. |
| CopyTo(Array, Int32) |
Copies items into an array. Only for Web Forms Interfaces. |
| Delete(Int32) |
Deletes a row at the specified index. |
| Dispose(Boolean) |
Disposes of the resources (other than memory) used by the DataView object. |
| EndInit() |
Ends the initialization of a DataView that is used on a form or used by another component. The initialization occurs at runtime. |
| Equals(DataView) |
Determines whether the specified DataView instances are considered equal. |
| Find(Object[]) |
Finds a row in the DataView by the specified sort key values. |
| Find(Object) |
Finds a row in the DataView by the specified sort key value. |
| FindRows(Object) |
Returns an array of DataRowView objects whose columns match the specified sort key value. |
| FindRows(Object[]) |
Returns an array of DataRowView objects whose columns match the specified sort key value. |
| GetEnumerator() |
Gets an enumerator for this DataView. |
| IndexListChanged(Object, ListChangedEventArgs) |
Occurs after a DataView has been changed successfully. |
| OnListChanged(ListChangedEventArgs) |
Raises the ListChanged event. |
| Open() |
Opens a DataView. |
| Reset() |
Reserved for internal use only. |
| ToTable(Boolean, String[]) |
Creates and returns a new DataTable based on rows in an existing DataView. |
| ToTable(String) |
Creates and returns a new DataTable based on rows in an existing DataView. |
| ToTable(String, Boolean, String[]) |
Creates and returns a new DataTable based on rows in an existing DataView. |
| ToTable() |
Creates and returns a new DataTable based on rows in an existing DataView. |
| UpdateIndex(Boolean) |
Reserved for internal use only. |
| UpdateIndex() |
Reserved for internal use only. |
Events
| Initialized |
Occurs when initialization of the DataView is completed. |
| ListChanged |
Occurs when the list managed by the DataView changes. |
Explicit Interface Implementations
Extension Methods
| Cast<TResult>(IEnumerable) | |
| OfType<TResult>(IEnumerable) | |
| AsParallel(IEnumerable) | |
| AsQueryable(IEnumerable) |
Thread Safety
This type is safe for multithreaded read operations. You must synchronize any write operations.