DataColumn Constructor (String, Type, String) (System.Data)

.NET Framework Class Library

DataColumn Constructor (String, Type, String)

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

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

Syntax

Visual Basic (Declaration)

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

Visual Basic (Usage)

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
)

Visual C++

public:
DataColumn(
    String^ columnName, 
    Type^ dataType, 
    String^ expr
)

JScript

public function DataColumn(
    columnName : String, 
    dataType : Type, 
    expr : String
)

Parameters

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

dataType: Type: System..::.Type
A supported DataType.

expr: Type: System..::.String
The expression used to create this column. For more information, see the Expression property.

Exceptions

Exception	Condition
ArgumentNullException	No dataType was specified.

Examples

The following example creates a computed column.

Visual Basic

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.
    table.Columns.Add(column)
 End Sub

private void AddDataColumn(DataTable table)
{
    System.Type decimalType;
    decimalType = System.Type.GetType("System.Decimal");

    // Create the column. The name is 'Tax,' with data type Decimal,and 
    // an expression ('UnitPrice * .0862) to calculate the tax.
    DataColumn column = new DataColumn("Tax", 
        decimalType, "UnitPrice * .0862");

    // Set various properties.
    column.AutoIncrement = false;
    column.ReadOnly = true;

    // Add to Columns collection.;
    table.Columns.Add(column);
}

Platforms

Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98, Windows CE, Windows Mobile for Smartphone, Windows Mobile for Pocket PC, Xbox 360, Zune

The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

Version Information