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DataColumn Constructor ( String, Type, String )
System.Data Namespace DataColumn Class
Initializes a new instance of the DataColumn class using the specified name, data type, and expression.
[ VB ] Overloads Public Sub New ( _ ByVal columnName As String, _ ByVal dataType As Type, _ ByVal expr As String _ ) [ C# ] public DataColumn ( string columnName, Type dataType, string expr ); [ C++ ] public: DataColumn ( String* columnName, Type* dataType, String* expr ); [ JScript ] public function DataColumn ( columnName : String, dataType : Type, expr : String );
Parameters
- columnName
- A string that represents the name of the column to be created. If set to a null reference or an empty string ( "" ), a default name will be given when added to the columns collection.
- dataType
- A supported DataType.
- expr
- The expression used to create this column. For more details, see the Expression property.
Exceptions
| Exception Type | Condition |
|---|---|
| ArgumentNullException | Occurs when no dataType is specified. |
Example
The following example initializes a computed column.
private void AddDataColumn ( ) {
System.Type dt new 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 myColumn = new DataColumn ( "Tax", dt, "UnitPrice * .0862" );
// set various properties.
myColumn.Unique = true;
myColumn.AutoIncrement = false;
myColumn.ReadOnly = true;
// add to Columns collection.;
myTable.Columns.Add ( myColumn );
}
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| C# | VB | |
See Also
DataColumn Members DataColumn Constructor Overload List DefaultValue ColumnName Caption DataTable DataType Expression
