BindingSource.Filter Property

 

Gets or sets the expression used to filter which rows are viewed.

Namespace:   System.Windows.Forms
Assembly:  System.Windows.Forms (in System.Windows.Forms.dll)

Public Overridable Property Filter As String

Property Value

Type: System.String

A string that specifies how rows are to be filtered. The default is null.

Typically used in complex data-binding scenarios, the Filter property allows you to view a subset of the DataSource. Only underlying lists that implement the IBindingListView interface support filtering.

When Filter is not null, the BindingSource passes this property to the underlying list. If you set this property during object initialization, the call will be deferred until after initialization is complete.

To form a filter value, specify the name of a column followed by an operator and a value to filter on. The accepted filter syntax depends on the underlying data source. If the underlying data source is a DataSet, DataTable, or DataView, you can specify Boolean expressions using the syntax documented for the DataColumn.Expression property.

The value of the Filter property affects the value of the Count property. Additionally, the Filter value will persist when the data source changes. To stop filtering the DataSource, call the RemoveFilter method.

The following example shows how to use the Filter property with a DataView. To run this example, paste the code into a Windows Form and call PopulateDataViewAndFilter from the form's constructor or Load event-handling method. Your form should import the System.Xml and System.IO namespaces.

Private Sub PopulateDataViewAndFilter() 
    Dim set1 As New DataSet()

    ' Some xml data to populate the DataSet with.
    Dim musicXml As String = "<?xml version='1.0' encoding='UTF-8'?>" & _
        "<music>" & _
        "<recording><artist>Coldplay</artist><cd>X&amp;Y</cd></recording>" & _
        "<recording><artist>Dave Matthews</artist><cd>Under the Table and Dreaming</cd></recording>" & _
        "<recording><artist>Dave Matthews</artist><cd>Live at Red Rocks</cd></recording>" & _
        "<recording><artist>Natalie Merchant</artist><cd>Tigerlily</cd></recording>" & _
        "<recording><artist>U2</artist><cd>How to Dismantle an Atomic Bomb</cd></recording>" & _
        "</music>"

    ' Read the xml.
    Dim reader As New StringReader(musicXml)
    set1.ReadXml(reader)

    ' Get a DataView of the table contained in the dataset.
    Dim tables As DataTableCollection = set1.Tables
    Dim view1 As New DataView(tables(0))

    ' Create a DataGridView control and add it to the form.
    Dim datagridview1 As New DataGridView()
    datagridview1.AutoGenerateColumns = True
    Me.Controls.Add(datagridview1)

    ' Create a BindingSource and set its DataSource property to
    ' the DataView.
    Dim source1 As New BindingSource()
    source1.DataSource = view1

    ' Set the data source for the DataGridView.
    datagridview1.DataSource = source1

    ' The Filter string can include Boolean expressions.
    source1.Filter = "artist = 'Dave Matthews' OR cd = 'Tigerlily'"

End Sub

.NET Framework
Available since 2.0
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