DataColumn.AllowDBNull DataColumn.AllowDBNull DataColumn.AllowDBNull DataColumn.AllowDBNull Property

定義

取得或設定值,指出對於屬於資料表的資料列而言,這個資料行中是否允許 Null 值。Gets or sets a value that indicates whether null values are allowed in this column for rows that belong to the table.

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

屬性值

true如果允許 null 值,則為,否則為falsetrue if null values are allowed; otherwise, false. 預設為 trueThe default is true.

範例

下列範例會建立新DataColumn的,並將其AllowDBNull屬性true設定為。The following example creates a new DataColumn and sets its AllowDBNull property to true.

private void AddNullAllowedColumn()
{
    DataColumn column;
    column = new DataColumn("classID", 
        System.Type.GetType("System.Int32"));
    column.AllowDBNull = true;

    // Add the column to a new DataTable.
    DataTable table;
    table = new DataTable();
    table.Columns.Add(column);
}
Private Sub AddNullAllowedColumn()
    Dim column As DataColumn
    column = New DataColumn("classID", _
        System.Type.GetType("System.Int32"))
    column.AllowDBNull = True

    ' Add the column to a new DataTable.
    Dim table As DataTable
    table = New DataTable
    table.Columns.Add(column)
End Sub

適用於

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