DataView.RowFilter Vlastnost

Definice

Obor názvů:

System.Data

Sestavení:

System.Data.Common.dll

Zdroj:

DataView.cs

Získá nebo nastaví výraz použitý k filtrování, které řádky jsou zobrazeny DataViewv .

public:
 virtual property System::String ^ RowFilter { System::String ^ get(); void set(System::String ^ value); };

public virtual string? RowFilter { get; set; }

member this.RowFilter : string with get, set

Public Overridable Property RowFilter As String

Hodnota vlastnosti

String

Řetězec, který určuje, jak mají být řádky filtrovány.

Příklady

Následující příklad vytvoří DataView a nastaví jeho RowFilter vlastnost.

using System;
using System.Data;
using System.Windows.Forms;

public class Form1 : Form {
   protected TextBox Text1;
   protected DataSet DataSet1;

   public static void Main() {
      DemostrateDataView();
   }

   private static void DemostrateDataView() {
      // Create a DataTable with one column
      DataTable dt = new DataTable("MyTable");
      DataColumn column = new DataColumn("Col", typeof(int));
      dt.Columns.Add(column);

      // Add 5 rows on Added state
      for (int i = 0; i < 5; i++) {
         DataRow row = dt.NewRow();
         row["Col"] = i;
         dt.Rows.Add(row);
      }

      // Add 5 rows on Unchanged state
      for (int i = 5; i < 10; i++) {
         DataRow row = dt.NewRow();
         row["Col"] = i;
         dt.Rows.Add(row);
         // Calling AcceptChanges will make the DataRowVersion change from Added to Unchanged in this case
         row.AcceptChanges();
      }

      // Create a DataView
      DataView dv = new DataView(dt);

      Console.WriteLine("Print unsorted, unfiltered DataView");
      PrintDataView(dv);

      // Changing the Sort order to descending
      dv.Sort = "Col DESC";

      Console.WriteLine("Print sorted DataView. Sort = 'Col DESC'");
      PrintDataView(dv);

      // Filter by an expression. Filter all rows where column 'Col' have values greater or equal than 3
      dv.RowFilter = "Col < 3";

      Console.WriteLine("Print sorted and Filtered DataView by RowFilter. RowFilter = 'Col > 3'");
      PrintDataView(dv);

      // Removing Sort and RpwFilter to ilustrate RowStateFilter. DataView should contain all 10 rows back in the original order
      dv.Sort = String.Empty;
      dv.RowFilter = String.Empty;

      // Show only Unchanged rows or last 5 rows
      dv.RowStateFilter = DataViewRowState.Unchanged;

      Console.WriteLine("Print Filtered DataView by RowState. RowStateFilter =  DataViewRowState.Unchanged");
      PrintDataView(dv);
   }

   private static void PrintDataView(DataView dv) {
      // Printing first DataRowView to demo that the row in the first index of the DataView changes depending on sort and filters
      Console.WriteLine("First DataRowView value is '{0}'", dv[0]["Col"]);

      // Printing all DataRowViews
      foreach (DataRowView drv in dv) {
         Console.WriteLine("\t {0}", drv["Col"]);
      }
   }
}

Imports System.Data
Imports System.Windows.Forms

Public Class Form1
    Inherits Form
    Protected Text1 As TextBox
    Protected DataSet1 As DataSet

    Public Shared Sub Main()
        DemostrateDataView()
    End Sub

    Private Shared Sub DemostrateDataView()
        ' Create a DataTable with one column
        Dim dt As New DataTable("MyTable")
        Dim column As New DataColumn("Col", GetType(Integer))
        dt.Columns.Add(column)

        ' Add 5 rows on Added state
        For i As Integer = 0 To 4
            Dim row As DataRow = dt.NewRow()
            row("Col") = i
            dt.Rows.Add(row)
        Next

        ' Add 5 rows on Unchanged state
        For i As Integer = 5 To 9
            Dim row As DataRow = dt.NewRow()
            row("Col") = i
            dt.Rows.Add(row)
            ' Calling AcceptChanges will make the DataRowVersion change from Added to Unchanged in this case
            row.AcceptChanges()
        Next

        ' Create a DataView
        Dim dv As New DataView(dt)

        Console.WriteLine("Print unsorted, unfiltered DataView")
        PrintDataView(dv)

        ' Changing the Sort order to descending
        dv.Sort = "Col DESC"

        Console.WriteLine("Print sorted DataView. Sort = 'Col DESC'")
        PrintDataView(dv)

        ' Filter by an expression. Filter all rows where column 'Col' have values greater or equal than 3
        dv.RowFilter = "Col < 3"

        Console.WriteLine("Print sorted and Filtered DataView by RowFilter. RowFilter = 'Col > 3'")
        PrintDataView(dv)

        ' Removing Sort and RpwFilter to ilustrate RowStateFilter. DataView should contain all 10 rows back in the original order
        dv.Sort = [String].Empty
        dv.RowFilter = [String].Empty

        ' Show only Unchanged rows or last 5 rows
        dv.RowStateFilter = DataViewRowState.Unchanged

        Console.WriteLine("Print Filtered DataView by RowState. RowStateFilter =  DataViewRowState.Unchanged")
        PrintDataView(dv)
    End Sub

    Private Shared Sub PrintDataView(dv As DataView)
        ' Printing first DataRowView to demo that the row in the first index of the DataView changes depending on sort and filters
        Console.WriteLine("First DataRowView value is '{0}'", dv(0)("Col"))

        ' Printing all DataRowViews
        For Each drv As DataRowView In dv
            Console.WriteLine(vbTab & " {0}", drv("Col"))
        Next
    End Sub
End Class

Poznámky

Pokud chcete vytvořit RowFilter hodnotu, zadejte název sloupce následovaného operátorem a hodnotu, podle které chcete filtrovat. Hodnota musí být v uvozovkách. Příklad:

"LastName = 'Smith'"

Další informace najdete ve ExpressionDataColumn vlastnosti třídy.

Pokud chcete vrátit pouze sloupce s hodnotami null, použijte následující výraz:

"Isnull(Col1;'Null Column') = 'Null Column'"

Viz také

• Expression
• Sort
• Datové sady, tabulky a zobrazení dat (ADO.NET)