System.Data.DataColumn

A DataColumn represents a single column (or field) in a DataTable (or in a DataRow).
All columns by default can contain Null values (assuming they are not primary keys.

Creating a DataColumn Object

Dim objDataColumn As System.Data.DataColumn 
objDataColumn = New System.Data.DataColumn 
objDataColumn.ColumnName = "NameOfColumn" 
objDataColumn.DataType = System.Type.GetType("System.String")

Alternatively you can pass the column name and the data type directly to the constructor

Dim objDataColumn As New System.Data.DataColumn("NameOfColumn", GetType(String))

Column DataTypes

objDataColumn.DataType = System.Type.GetType("System.String") 
objDataColumn.DataType = System.Type.GetType("System.Int32") 
objDataColumn.DataType = System.Type.GetType("System.Boolean") 
objDataColumn.DataType = System.Type.GetType("System.DateTime") 
objDataColumn.DataType = System.Type.GetType("System.Double") 
objDataColumn.DataType = System.Type.GetType("System.Decimal") 
objDataColumn.DataType = System.Type.GetType("System.Char") 
objDataColumn.DataType = System.Type.GetType("System.TimeSpan") 
objDataColumn.DataType = System.Type.GetType("System.Single") 
objDataColumn.DataType = System.Type.GetType("System.Int16")

Adding a DataColumn to a DataTable

objDataColumn.MaxLength = 100 
objDataTable.Columns.Add(objDataColumn)

Alternatively you can create an implicit DataColumn with the Columns.Add method

With objDataTable.Columns.Add("NameOfColumn", GetType(String)) 
   .MaxLength = 100 
End With 
'or even
objDataTable.Columns.Add("NameOfColumn", GetType(String)).MaxLength = 100

Creating an Expression

objDataColumn.Expression = "FirstName + LastName"

Properties

AllowDBNull	A boolean that determines whether null values can be accepted for this column. The default is True.
AutoIncrement	A boolean that determines whether this is an auto-incrementing column.
AutoIncrementSpeed	The starting value for an auto-incrementing column.
AutoIncrementStep	The increment value for an auto-incrementing column.
Caption	The caption to be used for this column in the user interface
ColumnMapping	The MappingType of this column, which is how this column is rendered as XML. It can be Element, Attribute, SimpleContent or Hidden.
ColumnName	The name of this column.
Container	An object implementing the IContainer interface that represents the component's container, or a null reference (Nothing in Visual Basic) if the component does not have a site.
DataType	The System.Type object that defines the data type of this column.
DefaultValue	The default value for this column when a new row is added to the table.
DesignMode
Expression	The expression to be used for calculated columns.
ExtendedProperties	Returns the PropertyCollection object used to store custom information about the DataColumn.
MaxLength	The maximum length of a text column.
Namespace	The namespace for this DataTable, used when importing or exporting XML data.
Ordinal	The position of this column in the DataColumnCollection
Prefix	The XML prefix for the DataTable namespace.
ReadOnly	A boolean that determines whether values in this column can be modified after the row has been added to the table.
Site
Table	The DataTable this column belongs to.
Unique	A boolean that determines whether duplicated values are accepted in this column.

Methods

Dispose
GetService
GetType
ToString