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 System.Data.dll)

public DataColumn Add(
	string columnName,
	Type type,
	string expression


Type: System.String

The name to use when you create the column.

Type: System.Type

The DataType of the new column.

Type: System.String

The expression to assign to the Expression property.

Return Value

Type: System.Data.DataColumn

The newly created DataColumn.

Exception Condition

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 null 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

.NET Framework
Available since 1.1
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