DataTable.WriteXmlSchema Method (TextWriter, Boolean)

 

Writes the current data structure of the DataTable as an XML schema using the specified TextWriter. To save the schema for the table and all its descendants, set the writeHierarchy parameter to true.

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

Public Sub WriteXmlSchema (
	writer As TextWriter,
	writeHierarchy As Boolean
)

Parameters

writer
Type: System.IO.TextWriter

The TextWriter with which to write.

writeHierarchy
Type: System.Boolean

If true, write the schema of the current table and all its descendants. If false (the default value), write the schema for the current table only.

Use the WriteXmlSchema method to write the schema for a DataTable to an XML document. The schema includes table, relation, and constraint definitions.

The XML schema is written using the XSD standard.

To write the data to an XML document, use the WriteXml method.

Normally the WriteXmlSchema method writes the schema only for the current table. To write the schema for the current table and its entire descendant, related tables, call the method with the writeHierarchy parameter set to true.

The following console application creates two DataTable instances, adds each to a DataSet, creates a DataRelation relating the two tables, and then uses the WriteXmlSchema method to write the data contained within the parent table to a TextWriter. The example demonstrates the behavior when setting the writeHierarchy parameter to each of its values.

Sub Main()
  Dim ds As New DataSet
  Dim customerTable As DataTable = GetCustomers()
  Dim orderTable As DataTable = GetOrders()

  ds.Tables.Add(customerTable)
  ds.Tables.Add(orderTable)
  ds.Relations.Add("CustomerOrder", _
   New DataColumn() {customerTable.Columns(0)}, _
   New DataColumn() {orderTable.Columns(1)}, True)

  Dim writer As New System.IO.StringWriter
  customerTable.WriteXmlSchema(writer, False)
  PrintOutput(writer, "Customer table, without hierarchy")

  writer = New System.IO.StringWriter
  customerTable.WriteXmlSchema(writer, True)
  PrintOutput(writer, "Customer table, with hierarchy")

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

Private Function GetOrders() As DataTable
  ' Create sample Customers table, in order
  ' to demonstrate the behavior of the DataTableReader.
  Dim table As New DataTable

  ' Create three columns, OrderID, CustomerID, and OrderDate.
  table.Columns.Add(New DataColumn("OrderID", GetType(System.Int32)))
  table.Columns.Add(New DataColumn("CustomerID", GetType(System.Int32)))
  table.Columns.Add(New DataColumn("OrderDate", GetType(System.DateTime)))

  ' Set the OrderID column as the primary key column.
  table.PrimaryKey = New DataColumn() {table.Columns(0)}

  table.Rows.Add(New Object() {1, 1, #12/2/2003#})
  table.Rows.Add(New Object() {2, 1, #1/3/2004#})
  table.Rows.Add(New Object() {3, 2, #11/13/2004#})
  table.Rows.Add(New Object() {4, 3, #5/16/2004#})
  table.Rows.Add(New Object() {5, 3, #5/22/2004#})
  table.Rows.Add(New Object() {6, 4, #6/15/2004#})
  table.AcceptChanges()
  Return table
End Function

Private Function GetCustomers() As DataTable
  ' Create sample Customers table, in order
  ' to demonstrate the behavior of the DataTableReader.
  Dim table As New DataTable

  ' Create two columns, ID and Name.
  Dim idColumn As DataColumn = table.Columns.Add("ID", _
      GetType(System.Int32))
  table.Columns.Add("Name", GetType(System.String))

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

  table.Rows.Add(New Object() {1, "Mary"})
  table.Rows.Add(New Object() {2, "Andy"})
  table.Rows.Add(New Object() {3, "Peter"})
  table.Rows.Add(New Object() {4, "Russ"})
  table.AcceptChanges()
  Return table
End Function

Private Sub PrintOutput( _
   ByVal writer As System.IO.TextWriter, ByVal caption As String)

  Console.WriteLine("==============================")
  Console.WriteLine(caption)
  Console.WriteLine("==============================")
  Console.WriteLine(writer.ToString())
End Sub

The example displays the following output in the console window:

==============================
Customer table, without hierarchy
==============================
<?xml version="1.0" encoding="utf-16"?>
<xs:schema id="NewDataSet" xmlns="" xmlns:xs="http://www.w3.org/2001/XMLSchema"
xmlns:msdata="urn:schemas-microsoft-com:xml-msdata">
  <xs:element name="NewDataSet" msdata:IsDataSet="true" msdata:MainDataTable="Ta
ble1">
    <xs:complexType>
      <xs:choice minOccurs="0" maxOccurs="unbounded">
        <xs:element name="Table1">
          <xs:complexType>
            <xs:sequence>
              <xs:element name="ID" type="xs:int" />
              <xs:element name="Name" type="xs:string" minOccurs="0" />
            </xs:sequence>
          </xs:complexType>
        </xs:element>
      </xs:choice>
    </xs:complexType>
    <xs:unique name="Constraint1" msdata:PrimaryKey="true">
      <xs:selector xpath=".//Table1" />
      <xs:field xpath="ID" />
    </xs:unique>
  </xs:element>
</xs:schema>
==============================
Customer table, with hierarchy
==============================
<?xml version="1.0" encoding="utf-16"?>
<xs:schema id="NewDataSet" xmlns="" xmlns:xs="http://www.w3.org/2001/XMLSchema"
xmlns:msdata="urn:schemas-microsoft-com:xml-msdata">
  <xs:element name="NewDataSet" msdata:IsDataSet="true" msdata:MainDataTable="Table1">
    <xs:complexType>
      <xs:choice minOccurs="0" maxOccurs="unbounded">
        <xs:element name="Table1">
          <xs:complexType>
            <xs:sequence>
              <xs:element name="ID" type="xs:int" />
              <xs:element name="Name" type="xs:string" minOccurs="0" />
            </xs:sequence>
          </xs:complexType>
        </xs:element>
        <xs:element name="Table2">
          <xs:complexType>
            <xs:sequence>
              <xs:element name="OrderID" type="xs:int" />
              <xs:element name="CustomerID" type="xs:int" minOccurs="0" />
              <xs:element name="OrderDate" type="xs:dateTime" minOccurs="0" />
            </xs:sequence>
          </xs:complexType>
        </xs:element>
      </xs:choice>
    </xs:complexType>
    <xs:unique name="Constraint1" msdata:PrimaryKey="true">
      <xs:selector xpath=".//Table1" />
      <xs:field xpath="ID" />
    </xs:unique>
    <xs:unique name="Table2_Constraint1" msdata:ConstraintName="Constraint1" msdata:PrimaryKey="true">
      <xs:selector xpath=".//Table2" />
      <xs:field xpath="OrderID" />
    </xs:unique>
    <xs:keyref name="CustomerOrder" refer="Constraint1">
      <xs:selector xpath=".//Table2" />
      <xs:field xpath="CustomerID" />
    </xs:keyref>
  </xs:element>
</xs:schema>

.NET Framework
Available since 2.0
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