System.Data Namespace   DataColumnCollection Class

---

Initializes and adds a DataColumn with the specified name, type, and expression to the columns collection.

[ VB ]
Overloads Public Function Add ( _
   ByVal columnName As String, _
   ByVal type As Type, _
   ByVal expression As String _
) As DataColumn

[ C# ]
public virtual DataColumn Add (
   string columnName,
   Type type,
   string expression
);

[ C++ ]
public: virtual DataColumn* Add (
   String* columnName,
   Type* type,
   String* expression
);

[ JScript ]
public function Add (
   columnName : String,
   type : Type,
   expression : String
) : DataColumn;

columnName

The name to give to the column.

type

The DataType of the column.

expression

The expression to assign to the Expression property.

The newly created DataColumn.

Exception Type	Condition
DuplicateNameException	The collection already has a column with the same name ( the comparison is not case-sensitive ).
InvalidExpressionException	The expression is invalid. See the Expression property for details on creating expressions.

If a null reference or an empty string ( "" ) is passed in for the name, a default name ( "Column1", "Column2", etc. ) 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 initializes and adds a new DataColumn to the DataColumnCollection of a DataTable using this constructor.

Private Sub AddColumn ( )
   ' get the DataColumnCollection of a table in a DataSet.
   Dim cols As DataColumnCollection = ds.Tables ( "Orders" ).Columns

   ' add a new column
   Dim myCol As DataColumn = cols.Add ( "Total", System.Type.GetType ( "System.Decimal" ), _
      "Price + Tax" )
   myCol.ReadOnly = True
   myCol.Unique = False
End Sub

DataColumnCollection Members   DataColumnCollection.Add Overload List   ColumnName   DataType   Expression

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