DataColumnCollection.Add Method (String, Type, String)

Creates and adds a DataColumn object that has the specified name, type, and expression to the DataColumnCollection.

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

public DataColumn Add (
	string columnName,
	Type type,
	string expression
public DataColumn Add (
	String columnName, 
	Type type, 
	String expression
public function Add (
	columnName : String, 
	type : Type, 
	expression : String
) : DataColumn
Not applicable.



The name to use when you create the column.


The DataType of the new column.


The expression to assign to the Expression property.

Return Value

The newly created DataColumn.

Exception typeCondition


The collection already has a column with the specified name. (The comparison is not case-sensitive.)


The expression is invalid. See the Expression property for more information about how to create expressions.

If a null reference (Nothing in Visual Basic) or an empty string ("") is passed in for the name, a default name ("Column1", "Column2", and so on) is given to the column.

Use the Contains method to determine whether a column with the proposed name already exists in the collection.

If the collection is successfully changed by adding or removing columns, the CollectionChanged event occurs.

The following example creates and adds a new DataColumn to a DataColumnCollection of a DataTable.

Private Sub AddColumn()
    ' Get the DataColumnCollection of a table in a DataSet.
    Dim columns As DataColumnCollection = _

    ' Add a new column and return it.
    Dim column As DataColumn = _
        columns.Add("Total", System.Type.GetType( _
        "System.Decimal"), "Price + Tax")
    column.ReadOnly = True
    column.Unique = False
 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

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