DataTable.CreateDataReader Método

Definição

Namespace:

System.Data

Assembly:

System.Data.Common.dll

Origem:

DataTable.cs

Retorna um DataTableReader correspondente aos dados nessa DataTable.

public:
 System::Data::DataTableReader ^ CreateDataReader();

public System.Data.DataTableReader CreateDataReader ();

member this.CreateDataReader : unit -> System.Data.DataTableReader

Public Function CreateDataReader () As DataTableReader

Retornos

DataTableReader

Um DataTableReader que contém um conjunto de resultados, correspondente à instância DataTable da origem.

Exemplos

O aplicativo de console a seguir cria uma instância DataTable. Em seguida, o exemplo passa o DataTable preenchido para um procedimento que chama o método CreateDataReader, que itera por meio dos resultados contidos no DataTableReader.

static void Main()
{
    TestCreateDataReader(GetCustomers());
    Console.WriteLine("Press any key to continue.");
    Console.ReadKey();
}

private static void TestCreateDataReader(DataTable dt)
{
    // Given a DataTable, retrieve a DataTableReader
    // allowing access to all the tables' data:
    using (DataTableReader reader = dt.CreateDataReader())
    {
        do
        {
            if (!reader.HasRows)
            {
                Console.WriteLine("Empty DataTableReader");
            }
            else
            {
                PrintColumns(reader);
            }
            Console.WriteLine("========================");
        } while (reader.NextResult());
    }
}

private static DataTable GetCustomers()
{
    // Create sample Customers table, in order
    // to demonstrate the behavior of the DataTableReader.
    DataTable table = new DataTable();

    // Create two columns, ID and Name.
    DataColumn idColumn = table.Columns.Add("ID", typeof(int));
    table.Columns.Add("Name", typeof(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" });
    return table;
}

private static void PrintColumns(DataTableReader reader)
{
    // Loop through all the rows in the DataTableReader
    while (reader.Read())
    {
        for (int i = 0; i < reader.FieldCount; i++)
        {
            Console.Write(reader[i] + " ");
        }
        Console.WriteLine();
    }
}

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

Private Sub TestCreateDataReader(ByVal dt As DataTable)
  ' Given a DataTable, retrieve a DataTableReader
  ' allowing access to all the tables's data:
  Using reader As DataTableReader = dt.CreateDataReader()
    Do
      If Not reader.HasRows Then
        Console.WriteLine("Empty DataTableReader")
      Else
        PrintColumns(reader)
      End If
      Console.WriteLine("========================")
    Loop While reader.NextResult()
  End Using
End Sub

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

Private Sub PrintColumns( _
   ByVal reader As DataTableReader)

  ' Loop through all the rows in the DataTableReader.
  Do While reader.Read()
    For i As Integer = 0 To reader.FieldCount - 1
      Console.Write(reader(i).ToString() & " ")
    Next
    Console.WriteLine()
  Loop
End Sub

O exemplo exibe a seguinte saída na janela do console:

1 Mary

2 Andy

3 Peter

4 Russ

Confira também

• CreateDataReader()
• DataTables