DataTableReader.HasRows 屬性

定義

命名空間:

System.Data

組件:

System.Data.Common.dll

來源:

DataTableReader.cs

取得值，指出 DataTableReader 是否包含一個或多個資料列。

public:
 virtual property bool HasRows { bool get(); };

public override bool HasRows { get; }

member this.HasRows : bool

Public Overrides ReadOnly Property HasRows As Boolean

屬性值

Boolean

如果 DataTableReader 包含一個或更多資料列，則為 true，否則為 false。

例外狀況

InvalidOperationException

嘗試擷取有關已關閉之 DataTableReader 的資訊。

範例

下列範例會將兩 DataTable 個實例填入數據。 第一個 DataTable 包含一個數據列，而第二個數據列則不包含任何數據列。 然後，此範例會建立包含這兩DataTable個DataTableReader物件的 ，並呼叫 PrintData 方法來顯示每個 物件的內容，並在呼叫 PrintData 之前檢查每個 屬性的值HasRows。

private static void TestHasRows()
{
    DataTable customerTable = GetCustomers();
    DataTable productTable = GetProducts();

    using (DataTableReader reader = new DataTableReader(
               new DataTable[] { customerTable, productTable }))
    {
        do
        {
            if (reader.HasRows)
            {
                PrintData(reader);
            }
        } while (reader.NextResult());
    }

    Console.WriteLine("Press Enter to finish.");
    Console.ReadLine();
}

private static void PrintData(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();
    }
}

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" });
    return table;
}

private static DataTable GetProducts()
{
    // Create sample Products 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 };
    return table;
}

Private Sub TestHasRows()
   'Retrieve one row from the Store table:
   Dim customerTable As DataTable = GetCustomers()
   Dim productsTable As DataTable = GetProducts()

   Using reader As New DataTableReader( _
      New DataTable() {customerTable, productsTable})

      Do
         If reader.HasRows Then
            PrintData(reader)
         End If
      Loop While reader.NextResult()
   End Using

   Console.WriteLine("Press Enter to finish.")
   Console.ReadLine()
End Sub

Private Sub PrintData( _
   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("{0} ", reader(i))
      Next
      Console.WriteLine()
   Loop
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"})
   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

   ' 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}

   Return table
End Function

備註

屬性 HasRows 會傳回目前結果集的相關信息。 DataTableReader如果 包含多個結果集，您可以在呼叫 NextResult 方法之後立即檢查 HasRows 屬性值，以判斷新的結果集是否包含數據列。

HasRows使用 屬性，以避免在目前結果集中沒有數據列時呼叫 Read 的 DataTableReader 方法。

另請參閱

• NextResult()
• Read()