DataSet.EnforceConstraints Proprietà

Definizione

Ottiene o imposta un valore che indica se vengono seguite le regole sui vincoli quando si esegue un'operazione di aggiornamento.Gets or sets a value indicating whether constraint rules are followed when attempting any update operation.

public:
 property bool EnforceConstraints { bool get(); void set(bool value); };
[System.Data.DataSysDescription("DataSetEnforceConstraintsDescr")]
public bool EnforceConstraints { get; set; }
member this.EnforceConstraints : bool with get, set
Public Property EnforceConstraints As Boolean

Valore della proprietà

trueSe vengono applicate le regole; in caso falsecontrario,.true if rules are enforced; otherwise, false. Il valore predefinito è true.The default is true.

Attributi

Eccezioni

Non è possibile attivare uno o più vincoli.One or more constraints cannot be enforced.

Esempi

Nell'esempio seguente viene creato DataSet un oggetto con una tabella, una colonna, cinque righe e UniqueConstraintuna.The following example creates a DataSet with one table, one column, five rows, and one UniqueConstraint. La EnforceConstraints proprietà è impostata su false e i valori di ogni riga sono impostati sullo stesso valore.The EnforceConstraints property is set to false and the values of each row are set to the same value. Quando la EnforceConstraints proprietà viene reimpostata su ConstraintException true, viene generato un oggetto.When the EnforceConstraints property is reset to true, a ConstraintException is generated.

private void DemonstrateEnforceConstraints()
{
    // Create a DataSet with one table, one column and 
    // a UniqueConstraint.
    DataSet dataSet= new DataSet("dataSet");
    DataTable table = new DataTable("table");
    DataColumn column = new DataColumn("col1");

    // A UniqueConstraint is added when the Unique 
    // property is true.
    column.Unique=true;
    table.Columns.Add(column);
    dataSet.Tables.Add(table);
    Console.WriteLine("constraints.count: " + 
        table.Constraints.Count);

    // add five rows.
    DataRow row ;
    for(int i=0;i<5;i++)
    {
        row = table.NewRow();
        row["col1"] = i;
        table.Rows.Add(row);
    }
    table.AcceptChanges();

    dataSet.EnforceConstraints=false;
    // Change the values of all rows to 1.
    foreach(DataRow thisRow in table.Rows)
    {
        thisRow["col1"]=1;
        //Console.WriteLine("\table" + thisRow[0]);
    }
    try
    {
        dataSet.EnforceConstraints=true;
    }
    catch(System.Data.ConstraintException e)
    {
        // Process exception and return.
        Console.WriteLine("Exception of type {0} occurred.", 
            e.GetType());
    }
}
Private Sub DemonstrateEnforceConstraints()
    ' Create a DataSet with one table, one column and 
    ' a UniqueConstraint.
    Dim dataSet As New DataSet("dataSet")
    Dim table As New DataTable("table")
    Dim column As New DataColumn("col1")
    column.Unique = True
    table.Columns.Add(column)
    dataSet.Tables.Add(table)
    Console.WriteLine("constraints.count: " _
        & table.Constraints.Count)

    ' add five rows.
    Dim row As DataRow
    Dim i As Integer
    For i = 0 To 4
       row = table.NewRow()
       row("col1") = i
       table.Rows.Add(row)
    Next
    table.AcceptChanges()
     
    dataSet.EnforceConstraints = False
    ' Change the values of all rows to 1.
    Dim thisRow As DataRow
    For Each thisRow In table.rows
       thisRow("col1") = 1
    Next
 
    Try
        dataSet.EnforceConstraints = True
    Catch e As System.Data.ConstraintException
        ' Process exception and return.
        Console.WriteLine("Exception of type {0} occurred.", _
            e.GetType().ToString())
    End Try
End Sub

Commenti

I DataTable vincoli vengono impostati al livello (Constraints proprietà).Constraints are set at the DataTable level (Constraints property). Per ulteriori informazioni sulla creazione di vincoli, vedere vincoli DataTable.For more information about creating constraints, see DataTable Constraints.

Si applica a

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