DataTable

A DataTable object resembles a database table and has a collection of DataColumns (i.e. fields) and DataRows (i.e. records).
It can also have a primary key based on one or more columns and a collection of Constraint objects which are useful for enforcing the uniqueness of the values in a column.
DataTable objects in a DataSet class are often tied to each other through relationships.
It is possible for a DataTable object to exist outside a DataSet class but it obviously cannot have any relationships.
The majority of applications will populate a DataTable directly from a database however it is possible to fill a datatable using code.

either created initially if defining primary keys
or implicitly using dataadapter.fill
tables("").beginloaddata
adapter.fill
tables("").endloaddata

Creating a DataTable Object

Dim objDataTable As System.Data.DataTable 
objDataTable = New System.Data.DataTable 
objDataTable.TableName = "DataTableName" 

Alternatively you could pass the name of the datatable string directly to the constructor

Dim objDataTable As New System.Data.DataTable("DataTableName") 

Retrieving a DataTable from a DataSet

Dim objDataTable As System.Data.DataTable 
objDataTable = objDataSet.Tables("DataTableName") 
objDataTable = objDataSet.Tables(0) 

Creating a Primary Key

This creates a primary key from a single column

objDataTable.PrimaryKey = obDataColumn 
objDataTable.PrimaryKey = objDataTable.Columns("UniqueID") 

This creates a primary key from two columns

Dim aobjDataColumns() As DataColumn = {objDataColumn1, objDataColumn2} 
objDataTable.PrimaryKey = aobjDataColumns 

Filtering, Searching and Sorting

There are two techniques you can use for filtering, searching and sorting the rows in a DataTable.
DataView object - This is explained in more detail on the DataView page.
objDataTable.Select - Takes up to three arguments, a filter expression, a sort criteria and a DataViewRowState enumerated value.

This performs a simple filter and returns an array of matching DataRow objects.

Dim objDataRows() As System.Data.DataRow 
objDataRows = objDataTable.Select("FirstName = 'Russell'")  

This performs a simple filter and sorts the matching DataRow objects by Age

objDataRows = objDataTable.Select("FirstName = 'Russell',  "Age DESC")  

This performs a simple filter and sort but only returns the DataRow objects that have been deleted.
The default DataViewRowState is CurrentRows.

objDataRows = objDataTable.Select("FirstName = 'Russell',  "Age DESC", DataViewRowState.Deleted)  

Properties

Methods

Events