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DataSet.Load Method (IDataReader, LoadOption, String[])

Note: This method is new in the .NET Framework version 2.0.

Fills a DataSet with values from a data source using the supplied IDataReader, using an array of strings to supply the names for the tables within the DataSet.

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

'Declaration
Public Sub Load ( _
	reader As IDataReader, _
	loadOption As LoadOption, _
	ParamArray tables As String() _
)
'Usage
Dim instance As DataSet
Dim reader As IDataReader
Dim loadOption As LoadOption
Dim tables As String()

instance.Load(reader, loadOption, tables)
public void Load (
	IDataReader reader, 
	LoadOption loadOption, 
	String[] tables
)
public function Load (
	reader : IDataReader, 
	loadOption : LoadOption, 
	... tables : String[]
)

Parameters

reader

An IDataReader that provides one or more result sets.

loadOption

A value from the LoadOption enumeration that indicates how rows already in the DataTable instances within the DataSet will be combined with incoming rows that share the same primary key.

tables

An array of strings, from which the Load method retrieves table name information.

The Load method provides a technique for filling a single DataTable with data, retrieved from an IDataReader instance. This method provides the same functionality, but allows you to load multiple result sets from an IDataReader into multiple tables within a DataSet.

The loadOption parameter allows you to specify how you want the imported data to interact with existing data, and can be any of the values from the LoadOption enumeration. See the documentation for the Load method for more information on using this parameter.

The tables parameter allows you to specify an array of table names, indicating the order of the tables corresponding to each result set loaded from the reader. The Load method attempts to find a table within the DataSet matching the name found in the array of table names, in order. If a matching table is found, that table is loaded with the content of the current result set. If no matching table is found, a table is created using the name supplied in the array of table names, and the new table's schema is inferred from the result set. After each result set, the Load method moves on to the next result set within the reader, until there are no more result sets.

The default namespace associated with DataSet, if any, is associated with each newly created DataTable. The name resolution scheme for this method is the same as that followed by the Fill method of the DbDataAdapter class.

The following Console application example first creates tables and loads data from a reader into a DataSet, using the Load method. The example then adds tables to a DataSet and attempts to fill the tables with data from a DataTableReader. In this example, because the parameters passed to the Load method indicate a table name that does not exist, the Load method creates a new table to match the name passed as a parameter. Once the data has been loaded, the example displays the contents of all its tables in the Console window.

Sub Main()
  Dim dataSet As New DataSet
  Dim table As DataTable

  Dim reader As DataTableReader = GetReader()

  ' The tables listed as parameters for the Load method 
  ' should be in the same order as the tables within the IDataReader.
  dataSet.Load(reader, LoadOption.Upsert, "Customers", "Products")
  For Each table In dataSet.Tables
    PrintColumns(table)
  Next

  ' Now try the example with the DataSet
  ' already filled with data:
  dataSet = New DataSet
  dataSet.Tables.Add(GetCustomers())
  dataSet.Tables.Add(GetProducts())

  ' Retrieve a data reader containing changed data:
  reader = GetReader()

  ' Load the data into the existing DataSet. Retrieve the order of the
  ' the data in the reader from the
  ' list of table names in the parameters. If you specify
  ' a new table name here, the Load method will create
  ' a corresponding new table.
  dataSet.Load(reader, LoadOption.Upsert, "NewCustomers", "Products")
  For Each table In dataSet.Tables
    PrintColumns(table)
  Next

  Console.WriteLine("Press any key to continue.")
  Console.ReadKey()
End Sub

Private Function GetCustomers() As DataTable
  ' Create sample Customers table.
  Dim table As New DataTable
  table.TableName = "Customers"

  ' Create two columns, ID and Name.
  Dim idColumn As DataColumn = table.Columns.Add("ID", GetType(Integer))
  table.Columns.Add("Name", GetType(String))

  ' Set the ID column as the primary key column.
  table.PrimaryKey = New DataColumn() {idColumn

  table.Rows.Add(New Object() {0, "Mary")
  table.Rows.Add(New Object() {1, "Andy")
  table.Rows.Add(New Object() {2, "Peter")
  table.AcceptChanges()
  Return table
End Function

Private Function GetProducts() As DataTable
  ' Create sample Products table, in order
  ' to demonstrate the behavior of the DataTableReader.
  Dim table As New DataTable
  table.TableName = "Products"

  ' Create two columns, ID and Name.
  Dim idColumn As DataColumn = table.Columns.Add("ID", GetType(Integer))
  table.Columns.Add("Name", GetType(String))

  ' Set the ID column as the primary key column.
  table.PrimaryKey = New DataColumn() {idColumn

  table.Rows.Add(New Object() {0, "Wireless Network Card")
  table.Rows.Add(New Object() {1, "Hard Drive")
  table.Rows.Add(New Object() {2, "Monitor")
  table.Rows.Add(New Object() {3, "CPU")
  Return table
End Function

Private Function GetReader() As DataTableReader
  ' Return a DataTableReader containing multiple
  ' result sets, just for the sake of this demo.
  Dim dataSet As New DataSet
  dataSet.Tables.Add(GetCustomers())
  dataSet.Tables.Add(GetProducts())
  Return dataSet.CreateDataReader()
End Function

Private Sub PrintColumns( _
   ByVal table As DataTable)

  Console.WriteLine()
  Console.WriteLine(table.TableName)
  Console.WriteLine("=========================")
  ' Loop through all the rows in the table.
  For Each row As DataRow In table.Rows
    For Each col As DataColumn In table.Columns
      Console.Write(row(col).ToString() & " ")
    Next
    Console.WriteLine()
  Next
End Sub

The example displays the following text in the Console window:


Customers
=========================
0 Mary
1 Andy
2 Peter

Products
=========================
0 Wireless Network Card
1 Hard Drive
2 Monitor
3 CPU

Customers
=========================
0 Mary
1 Andy
2 Peter

Products
=========================
0 Wireless Network Card
1 Hard Drive
2 Monitor
3 CPU

NewCustomers
=========================
0 Mary
1 Andy
2 Peter

Windows 98, Windows 2000 SP4, Windows CE, Windows Millennium Edition, Windows Mobile for Pocket PC, Windows Mobile for Smartphone, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

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

.NET Framework

Supported in: 2.0

.NET Compact Framework

Supported in: 2.0

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