DbSeekOptions 列舉

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指定 Seek 方法如何在索引上搜尋的選項。

此列舉有一個允許其成員值為位元組合的 FlagsAttribute 屬性。

命名空間：  System.Data.SqlServerCe
組件：  System.Data.SqlServerCe (在 System.Data.SqlServerCe.dll 中)

語法

'宣告
<FlagsAttribute> _
Public Enumeration DbSeekOptions
'用途
Dim instance As DbSeekOptions

[FlagsAttribute]
public enum DbSeekOptions

[FlagsAttribute]
public enum class DbSeekOptions

[<FlagsAttribute>]
type DbSeekOptions

public enum DbSeekOptions

成員

成員名稱 說明
FirstEqual 前移到索引上第一個符合的資料列 (按照索引順序)。
LastEqual 前移到索引上最後一個符合的資料列 (按索引順序)。
AfterEqual 前移至索引上最後一個符合的資料列。如果沒有符合的資料列，則按照索引順序，前移到具有搜尋值後面之值的第一個資料列。
After 前移到第一個資料列，該資料列具有搜尋值後面的值 (按照索引順序)。
BeforeEqual 前移到索引上第一個符合的資料列。如果沒有符合的值，則按照索引順序，前移到具有搜尋值前面之值的最後一個資料列。
Before 前移到最後一個資料列，該資料列具有搜尋值後面的值 (按照索引順序)。

範例

在此範例中，會針對索引上的 Seek 作業指定 FirstEqual 選項。

        Try
            Dim conn As New SqlCeConnection("Data Source = MyDatabase.sdf")
            conn.Open()

            Dim cmd As SqlCeCommand = conn.CreateCommand()
            cmd.CommandType = CommandType.TableDirect
            cmd.IndexName = "Orders_PK"
            cmd.CommandText = "Orders"

            ' We are interested in orders that match Order ID = 10020
            '
            cmd.SetRange(DbRangeOptions.Match, New Object() {10020}, Nothing)

            Dim reader As SqlCeDataReader = cmd.ExecuteReader(CommandBehavior.Default)

            While reader.Read()
                MessageBox.Show(String.Format("{0} ; {1}", reader("Order ID"), reader("Order Date")))
            End While

            ' Now we are interested in orders with Order ID between (10020, 10050)
            '
            cmd.SetRange(DbRangeOptions.InclusiveStart Or DbRangeOptions.InclusiveEnd, New Object() {10020}, New Object() {10050})

            reader = cmd.ExecuteReader(CommandBehavior.Default)

            ' Now seek to Order ID = 10045
            '
            Dim onRow As Boolean =  reader.Seek(DbSeekOptions.FirstEqual, New Object() {10045})

            ' Now ,the reader will return rows with Order ID >= 10045 <= 10050
            ' because the range was set to (10020, 10050)
            '
            If onRow Then
                While reader.Read()
                    MessageBox.Show(String.Format("{0} ; {1}", reader("Order ID"), reader("Order Date")))
                End While
            End If
        Catch e As Exception
            MessageBox.Show(e.Message)
        End Try

        try
        {
            SqlCeConnection conn = new SqlCeConnection("Data Source = MyDatabase.sdf");
            conn.Open();

            SqlCeCommand cmd = conn.CreateCommand();
            cmd.CommandType = CommandType.TableDirect;
            cmd.IndexName = "Orders_PK";
            cmd.CommandText = "Orders";

            // We are interested in orders that match Order ID = 10020
            //
            cmd.SetRange(DbRangeOptions.Match, new object[] { 10020 }, null);

            SqlCeDataReader reader = cmd.ExecuteReader(CommandBehavior.Default);

            for (int i = 1; reader.Read(); i++)
            {
                MessageBox.Show(String.Format("{0} ; {1}", reader["Order ID"], reader["Order Date"]));
            }

            // Now we are interested in orders with Order ID between (10020, 10050)
            //
            cmd.SetRange(DbRangeOptions.InclusiveStart | DbRangeOptions.InclusiveEnd,
                new object[] { 10020 }, new object[] { 10050 });

            reader = cmd.ExecuteReader(CommandBehavior.Default);

            // Now seek to Order ID = 10045
            //
            bool onRow = reader.Seek(DbSeekOptions.FirstEqual, new object[] { 10045 });

            // Now ,the reader will return rows with Order ID >= 10045 <= 10050
            // because the range was set to (10020, 10050)
            //
            if (onRow)
            {
                for (int i = 1; reader.Read(); i++)
                {
                    MessageBox.Show(String.Format("{0} ; {1}", reader["Order ID"], reader["Order Date"]));
                }
            }
        }
        catch (Exception e)
        {
            MessageBox.Show(e.Message);
        }

請參閱

參考

System.Data.SqlServerCe 命名空間