StateChangeEventArgs クラスとは何？わかりやすく解説 Weblio辞書

.NET Framework クラスライブラリリファレンス

索引トップ用語の索引ランキング

StateChangeEventArgs クラス

.NET Framework データプロバイダの状態変化イベントにデータを提供します。

名前空間: System.Data
アセンブリ: System.Data (system.data.dll 内)
構文

Visual Basic (宣言)

Public NotInheritable Class
 StateChangeEventArgs
    Inherits EventArgs

Visual Basic (使用法)

Dim instance As StateChangeEventArgs

public sealed class StateChangeEventArgs :
 EventArgs

C++

public ref class StateChangeEventArgs sealed
 : public EventArgs

public final class StateChangeEventArgs extends
 EventArgs

JScript

public final class StateChangeEventArgs extends
 EventArgs

解説

このデータは、OleDbConnection の StateChange プロパティと SqlConnection の StateChange プロパティによって使用されます。

使用例

SqlConnection クラス内で StateChange イベントを使用する方法を次の例に示します。

Visual Basic

' Handler for the OnStateChange event.
Private Sub OnStateChange(ByVal
 sender As Object, _
    ByVal e As StateChangeEventArgs)
    PrintEventArgs(e)
End Sub

Sub Main()
    FillDataSet()
End Sub

Private Sub FillDataSet()
    Dim connectionString As String
 = GetConnectionString()
    Dim queryString As String
 = _
        "SELECT ProductID, UnitPrice from dbo.Products;"

    ' Create a DataAdapter.
    Using dataAdapter As New SqlDataAdapter(
 _
        queryString, connectionString)

        ' Add the handlers.
        AddHandler dataAdapter.SelectCommand.Connection.StateChange,
 _
            AddressOf OnStateChange

        ' Create a DataSet.
        Dim dataSet As New
 DataSet()

        ' Fill the DataSet, which fires several StateChange events.
        dataAdapter.Fill(dataSet, 0, 5, "Table")
    End Using
End Sub

Private Sub PrintEventArgs(ByVal
 args As StateChangeEventArgs)
    Console.WriteLine("StateChangeEventArgs")
    Console.WriteLine("  OriginalState= {0} CurrentState= {1}",
 _
        args.OriginalState, args.CurrentState)
End Sub

Private Function GetConnectionString() As
 String
    ' To avoid storing the connection string in your code,  
    ' you can retrieve it from a configuration file.
    Return "Data Source=(local);Initial Catalog=Northwind;"
 _
       & "Integrated Security=true;"
End Function

// Handler for OnStateChange event.
protected static void OnStateChange(object
 sender,
    StateChangeEventArgs e)
{
    PrintEventArgs(e);
}

static void Main()
{
    FillDataSet();
}

static private void FillDataSet()
{
    string connectionString = GetConnectionString();
    string queryString =
        "SELECT ProductID, UnitPrice from dbo.Products;";

    // Create a DataAdapter.
    using (SqlDataAdapter dataAdapter =
               new SqlDataAdapter(queryString, connectionString))
    {

        // Add the handlers.
        dataAdapter.SelectCommand.Connection.StateChange
            += new StateChangeEventHandler(OnStateChange);

        // Create a DataSet.
        DataSet dataSet = new DataSet();

        // Fill the DataSet, which fires several StateChange events.
        dataAdapter.Fill(dataSet, 0, 5, "Table");
    }
}

protected static void PrintEventArgs(StateChangeEventArgs
 args)
{
    Console.WriteLine("StateChangeEventArgs");
    Console.WriteLine("  OriginalState= {0} CurrentState= {1}",
        args.OriginalState, args.CurrentState);
}

static private string GetConnectionString()
{
    // To avoid storing the connection string in your code, 
    // you can retrieve it from a configuration file.
    return "Data Source=(local);Initial Catalog=Northwind;"
        + "Integrated Security=true";
}