n Overloads Public Overridable Function Add() As DataColumn
n Overloads Public Sub Add(ByVal column As DataColumn )
n Overloads Public Overridable Function Add(ByVal columnName As String ) As DataColumn
n Overloads Public Overridable Function Add(ByVal columnName As String , ByVal type As Type ) As DataColumn
n Overloads Public Overridable Function Add(ByVal columnName As String , ByVal type As Type ,ByVal expression As String ) As DataColumn
参数
1. columnName 列的名称。
2. column 要添加的 DataColumn 。
3. type 新列的 DataType 。
4. expression 要分配给 Expression 属性的表达式。
DataColumnCollection 定义 DataTable 的架构，并确定每个 DataColumn 可以包含什么种类的数据。可以通过 DataTable 对象的 Columns 属性访问 DataColumnCollection 。
DataColumnCollection 使用 Add 和 Remove 方法插入和删除 DataColumn 对象。使用 Count 属性确定集合中有多少 DataColumn 对象。使用 Contains 方法验证集合中是否存在指定索引或列名称。
示例
Private Sub AddColumn()
Dim cols As DataColumnCollection= DataSet1.Tables("Orders").Columns
Dim myCol As DataColumn
myCol = cols.Add ()
With myCol
.DataType = System.Type.GetType("System.Decimal")
.ColumnName = "Total"
.Expression = "UnitPrice * Quantity"
.ReadOnly = True
.Unique = False
End With
myCol = New DataColumn
With myCol
.DataType = System.Type.GetType("System.Decimal")
.ColumnName = "Total"
.Expression = "UnitPrice * Quantity"
.ReadOnly = True
.Unique = False
End With
cols.Add( myCol )
myCol = cols.Add( "Total", System.Type.GetType("System.Decimal"), "UnitPrice * Quantity" )
myCol.ReadOnly = True
myCol.Unique = False
myCol = cols.Add( "Total" )
With myCol
.DataType = System.Type.GetType("System.Decimal")
.ReadOnly = True
.Expression = "UnitPrice * Quantity"
.Unique = False
End With
myCol = cols.Add( "Total", System.Type.GetType("System.Decimal") )
myCol.Expression = "UnitPrice * Quantity"
myCol.ReadOnly = True
myCol.Unique = False
Dim col As DataColumn
For Each col in cols
Console.WriteLine(col.ColumnName)
Console.WriteLine(col.DataType.ToString)
Next
End Sub