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DataColumn::DataType Property

Gets or sets the type of data stored in the column.

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

property Type^ DataType {
	Type^ get ();
	void set (Type^ value);

Property Value

Type: System::Type
A Type object that represents the column data type.


The column already has data stored.

- or -

AutoIncrement is true, but the value is set to a type a unsupported by AutoIncrement.

Setting the DataType value is very important to guaranteeing the correct creation and updating of data in a data source.

The DataType property supports the following base .NET Framework data types:

as well as the following array type:

  • Byte[]

An exception is generated when changing this property after the column has begun storing data.

If AutoIncrement is set to true before setting the DataType property, and you try to set the type to anything except an integer type, an exception is generated.


A column of data type Byte[] requires special treatment in certain cases since, unlike the base .NET Framework data types, it is a reference data type. If a column of data type Byte[] is used as a PrimaryKey, or as a Sort or RowFilter key for a DataView, any change to the column value must involve assigning the Byte[] column value to a separately instantiated Byte[] object. This assignment is required to trigger the update of the internal indexes used by sorting, filtering, and primary key operations. This is illustrated by the following example:

byte[] columnValue = (byte[])myDataTable.Rows[0][0];
byte[] newValue = (byte[])columnValue.Clone();
newValue[1] = 2;
myDataTable.Rows[0][0] = newValue;

Although it is possible to define a column as data type other than the base .NET Framework data types and Byte[], such a column will be treated as a user-defined type, subject to the following usage restrictions. (For more information on user-defined types, see Creating and Using User-Defined Types.)

  • The column cannot be part of a RowFilter or Select expression.

  • If the column is used as a PrimaryKey, or as a Sort or for a DataView, it must be treated as an immutable field; the column data must not be changed once it has been added to the table.

  • Its ColumnMapping can be only set to MappingType.Element.

  • The class that implements the column’s data type must be must be marked with the SerializableAttribute, and if necessary implement the ISerializable or IXmlSerializable interface.

  • Support for change tracking is limited. To utilize the DataTable class’s change tracking mechanism, the class that implements the column’s data type must either implement the IChangeTracking interface, or take over the responsibility for informing the DataRow when the column value has been modified, either by calling SetModified on the row or by assigning the column value object to a separately instantiated column value object.

The following example adds columns of several data types to a DataTable, and then adds one row to the table.

No code example is currently available or this language may not be supported.

Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98, Windows CE, Windows Mobile for Smartphone, Windows Mobile for Pocket PC, Xbox 360, Zune

The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

.NET Framework

Supported in: 3.5, 3.0, 2.0, 1.1, 1.0

.NET Compact Framework

Supported in: 3.5, 2.0, 1.0

XNA Framework

Supported in: 3.0, 2.0, 1.0