DataSet.EnforceConstraints 屬性

定義

命名空間:

System.Data

組件:

System.Data.Common.dll

來源:

DataSet.cs

取得或設定值，指出在嘗試任何更新作業時，是否遵循條件約束 (Constraint) 規則。

public:
 property bool EnforceConstraints { bool get(); void set(bool value); };

public bool EnforceConstraints { get; set; }

member this.EnforceConstraints : bool with get, set

Public Property EnforceConstraints As Boolean

屬性值

Boolean

true 如果強制執行規則，則為 ;否則為 false。 預設為 true。

例外狀況

ConstraintException

一個或多個條件約束無法強制遵循。

範例

下列範例會 DataSet 建立具有一個資料表、一個資料行、五個資料列和一個 UniqueConstraint的 。 屬性 EnforceConstraints 設定為 false ，而且每個數據列的值都設定為相同的值。 EnforceConstraints當 屬性重設為 true時，ConstraintException會產生 。

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

備註

條件約束是在層級 (Constraints 屬性) 設定DataTable。 如需建立條件約束的詳細資訊，請參閱 DataTable 條件約束。

另請參閱

• 在 ADO.NET 中使用數據集