n IsNull方法
n Overloads Public Function IsNull(ByVal column As DataColumn ) As Boolean
n Overloads Public Function IsNull(ByVal columnIndex As Integer ) As Boolean
n Overloads Public Function IsNull(ByVal columnName As String ) As Boolean
n Overloads Public Function IsNull(ByVal column As DataColumn, ByVal version As DataRowVersion ) As Boolean
参数
1. column DataColumn。
2. columnIndex 列的从零开始的索引。
3. columnName 列的名称。
4. version DataRowVersion 值之一,它指定行版本。可能值为 Default、Original、Current 和 Proposed。
示例1
以下示例将列的值更改为空值,然后使用 IsNull 方法来确定该值是否为空。
Private Sub IsValNull()
Dim t As DataTable
Dim r As DataRow
'''' Assuming the DataGrid is bound to a DataTable.
t = CType(DataGrid1.DataSource, DataTable)
r = t.Rows(datagrid1.CurrentCell.RowNumber)
r.BeginEdit
r("FirstName") = System.DBNull.Value’ r(1) = System.DBNull.Value
r.EndEdit
r.AcceptChanges
Console.WriteLine(r.IsNull("FirstName"))’ Console.WriteLine(r.IsNull(1))
End Sub
示例2
Private Sub PrintRows(ds As DataSet)
Dim c As DataColumn
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