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DataColumn.DataColumn(String, Type, String) Constructor

Initializes a new instance of the DataColumn class using the specified name, data type, and expression.

Namespace: System.Data
Assembly: System.Data (in

Public Sub New ( _
	columnName As String, _
	dataType As Type, _
	expr As String _
Dim columnName As String
Dim dataType As Type
Dim expr As String

Dim instance As New DataColumn(columnName, dataType, expr)
public DataColumn (
	String columnName, 
	Type dataType, 
	String expr
public function DataColumn (
	columnName : String, 
	dataType : Type, 
	expr : String
Not applicable.



A string that represents the name of the column to be created. If set to a null reference (Nothing in Visual Basic) or an empty string (""), a default name will be specified when added to the columns collection.


A supported DataType.


The expression used to create this column. For more information, see the Expression property.

Exception typeCondition


No dataType was specified.

The following example creates a computed column.

Private Sub AddDataColumn(ByVal table As DataTable)
    Dim column As DataColumn 
    Dim decimalType As System.Type
    decimalType = System.Type.GetType("System.Decimal")
    column = New DataColumn("Tax", decimalType, "UnitPrice * .0862")

    ' Set various properties.
    With column
       .AutoIncrement = False
       .ReadOnly = True
    End With

    ' Add to Columns collection.
 End Sub

Windows 98, Windows Server 2000 SP4, Windows CE, Windows Millennium Edition, Windows Mobile for Pocket PC, Windows Mobile for Smartphone, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The Microsoft .NET Framework 3.0 is supported on Windows Vista, Microsoft Windows XP SP2, and Windows Server 2003 SP1.

.NET Framework

Supported in: 3.0, 2.0, 1.1, 1.0

.NET Compact Framework

Supported in: 2.0, 1.0

XNA Framework

Supported in: 1.0